Tkool Electronics

FAQWhatisl293d?L293DICisadualH-bridgemotordriverIC.OneH-bridgeiscapabletodriveadcmotorinbidirectional.L293DICisacurrentenhancingICastheoutputfromthesensorisnotabletodrivemotorsitselfsoL293Disusedforthispurpose.Whichisbetterl293dvsl298n?L293DDriversOperatesat4.5Vto36VwhereasL298NcanbeOperatesatupto46V.Maximum600mACurrentcanbedrawnthroughbothchannelsofL293DwhereasL298NMotorDrivercandrawupto2Afrombothchannels.WhatistheuseofEnablepininl293d?L293DhasanenablefacilitywhichhelpsyouenabletheICoutputpins.Ifanenablepinissettologichigh,thenstateoftheinputsmatchthestateoftheoutputs.Ifyoupullthislow,thentheoutputswillbeturnedoffregardlessoftheinputstates.HowmanyDCmotorscanbecontrolledbyanICl293d?TheL293Disa16-pinMotorDriverICwhichcancontroluptotwoDCmotorssimultaneously,inanydirection.HowdoIconnectmyArduinotol293d?Connect5VtoEnable1,Vss,andVsontheL293D.Connectdigitaloutputpins(wereusing6and7)toinput1andinput2ontheL293D.ConnectyourArduinosGNDtobothGNDpinsonthesamesideoftheL293D.Finally,connectoutput1andoutput2oftheL293Dtoyourmotorpins.WhatisHbridgeinl293d?H-BridgeCircuit.AHbridgeisanelectroniccircuitthatallowsavoltagetobeappliedacrossaloadinanydirection.H-bridgecircuitsarefrequentlyusedinroboticsandmanyotherapplicationstoallowDCmotorstorunforwardbackward.WhatisthefunctionofHbridge?AnH-bridgeisanelectroniccircuitthatswitchesthepolarityofavoltageappliedtoaload.ThesecircuitsareoftenusedinroboticsandotherapplicationstoallowDCmotorstorunforwardsorbackwards.Whatisl293dmotordrivershield?L293DshieldisadriverboardbasedonL293IC,whichcandrive4DCmotorsand2stepperorServomotorsatthesametime.Eachchannelofthismodulehasthemaximumcurrentof1.2Aanddoesntworkifthevoltageismorethan25vorlessthan4.5v.HowdoIusethel293dmotordrivermodule?Connect5VtoEnable1,Vss,andVsontheL293D.Connectdigitaloutputpins(wereusing6and7)toinput1andinput2ontheL293D.ConnectyourArduinosGNDtobothGNDpinsonthesamesideoftheL293D.Whatisthedifferencebetweenl293dandl298n?L293isquadruplehalf-HdriverwhileL298isdualfull-Hdriver,i.e,inL293allfourinput-outputlinesareindependentwhileinL298,ahalfHdrivercannotbeusedindependently,onlyfullHdriverhastobeused....Hence,heatsinkisprovidedinL298.。

IRLU120PBF-VISHAY

FAQWhatisl293d?L293DICisadualH-bridgemotordriverIC.OneH-bridgeiscapabletodriveadcmotorinbidirectional.L293DICisacurrentenhancingICastheoutputfromthesensorisnotabletodrivemotorsitselfsoL293Disusedforthispurpose.Whichisbetterl293dvsl298n?L293DDriversOperatesat4.5Vto36VwhereasL298NcanbeOperatesatupto46V.Maximum600mACurrentcanbedrawnthroughbothchannelsofL293DwhereasL298NMotorDrivercandrawupto2Afrombothchannels.WhatistheuseofEnablepininl293d?L293DhasanenablefacilitywhichhelpsyouenabletheICoutputpins.Ifanenablepinissettologichigh,thenstateoftheinputsmatchthestateoftheoutputs.Ifyoupullthislow,thentheoutputswillbeturnedoffregardlessoftheinputstates.HowmanyDCmotorscanbecontrolledbyanICl293d?TheL293Disa16-pinMotorDriverICwhichcancontroluptotwoDCmotorssimultaneously,inanydirection.HowdoIconnectmyArduinotol293d?Connect5VtoEnable1,Vss,andVsontheL293D.Connectdigitaloutputpins(wereusing6and7)toinput1andinput2ontheL293D.ConnectyourArduinosGNDtobothGNDpinsonthesamesideoftheL293D.Finally,connectoutput1andoutput2oftheL293Dtoyourmotorpins.WhatisHbridgeinl293d?H-BridgeCircuit.AHbridgeisanelectroniccircuitthatallowsavoltagetobeappliedacrossaloadinanydirection.H-bridgecircuitsarefrequentlyusedinroboticsandmanyotherapplicationstoallowDCmotorstorunforwardbackward.WhatisthefunctionofHbridge?AnH-bridgeisanelectroniccircuitthatswitchesthepolarityofavoltageappliedtoaload.ThesecircuitsareoftenusedinroboticsandotherapplicationstoallowDCmotorstorunforwardsorbackwards.Whatisl293dmotordrivershield?L293DshieldisadriverboardbasedonL293IC,whichcandrive4DCmotorsand2stepperorServomotorsatthesametime.Eachchannelofthismodulehasthemaximumcurrentof1.2Aanddoesntworkifthevoltageismorethan25vorlessthan4.5v.HowdoIusethel293dmotordrivermodule?Connect5VtoEnable1,Vss,andVsontheL293D.Connectdigitaloutputpins(wereusing6and7)toinput1andinput2ontheL293D.ConnectyourArduinosGNDtobothGNDpinsonthesamesideoftheL293D.Whatisthedifferencebetweenl293dandl298n?L293isquadruplehalf-HdriverwhileL298isdualfull-Hdriver,i.e,inL293allfourinput-outputlinesareindependentwhileinL298,ahalfHdrivercannotbeusedindependently,onlyfullHdriverhastobeused....Hence,heatsinkisprovidedinL298.。

Description74LS138isa3-lineto8-linedecoder/demultiplexer.Thechipisdesignedtobeusedinhigh-performancememory-decodingordata-routingapplications,requiringveryshortpropagationdelaytimes.Inhighperformancememorysystemsthesedecoderscanbeusedtominimizetheeffectsofsystemdecoding.Thethreeenablepinsofchip(inwhichTwoactive-lowandoneactive-high)reducetheneedforexternalgatesorinverterswhenexpanding.A24-linedecodercanbeimplementedwithnoexternalinverters,anda32-linedecoderrequiresonlyoneinverter.74LS138isusedinde-multiplexingapplicationsbyusingenablepinasdatainputpin.Alsothechipinputsareclampedwithhigh-performanceSchottkydiodestosuppressline-ringingandsimplifysystemdesign.CatalogDescriptionCatalogCADModelsFeaturesApplicationPinoutLogicDiagramPackageParametersProductComplianceComponentDatasheetProductManufacturerFAQOrdering&QuantityCADModels74LS138Symbol74LS138FootprintFeaturesDesignedSpecificallyforHigh-Speed:MemoryDecodersDataTransmissionSystems3EnableInputstoSimplifyCascadingand/orDataReceptionSchottky-ClampedforHighPerformanceApplicationLinedecodersServersDigitalsystemsLineDe-multiplexingTelecomcircuitsMemorycircuitsPinoutPinFunctionPinNameDescription1A0Addressinputpin2A1Addressinputpin3A2Addressinputpin4E1Enableinput(activeLOW)5E2Enableinput(activeLOW)6E3Enableinput(activeHIGH)7O7Outputpin78GNDGround9O6Outputpin610O5Outputpin511O4Outputpin412O3Outputpin313O2Outputpin214O1Outputpin115O0Outputpin016VCCPowersupplypinLogicDiagramPackageParametersFunctionDecoder,DemultiplexerTechnologyFamilyLSVCC(Min)(V)4.75VCC(Max)(V)5.25Channels(#)1Voltage(Nom)(V)5F@nomvoltage(Max)(MHz)35ICC@nomvoltage(Max)(mA)10tpd@nomVoltage(Max)(ns)41Configuration3:8ProducttypeStandardIOL(Max)(mA)8IOH(Max)(mA)-0.4RatingCatalogOperatingtemperaturerange(C)0to70Bits(#)8Digitalinputleakage(Max)(uA)5ESDCDM(kV)0.75ESDHBM(kV)2ProductComplianceECCNEAR99USHTS8542390001ComponentDatasheetDatasheet74LS138DatasheetProductManufacturerTexasInstrumentsInc.(TI)isanAmericantechnologycompanythatdesignsandmanufacturessemiconductorsandvariousintegratedcircuits,whichitsellstoelectronicsdesignersandmanufacturersglobally.ItsheadquartersareinDallas,Texas,UnitedStates.TIisoneofthetoptensemiconductorcompaniesworldwide,basedonsalesvolume.TexasInstrumentssfocusisondevelopinganalogchipsandembeddedprocessors,whichaccountsformorethan80%oftheirrevenue.TIalsoproducesTIdigitallightprocessing(DLP)technologyandeducationtechnologyproductsincludingcalculators,microcontrollersandmulti-coreprocessors.Todate,TIhasmorethan43,000patentsworldwide.FAQWhatisthedifferencebetween74hc138and74LS138?Bothhavethesamefunction.74HC138ismadeofhigh-speedCMOSprocess,withlowpowerconsumption,highoutput,lowlevelandwiderange.74LS138adoptstheearlybipolarprocess,anditsdrivingcapabilityisrelativelylarger.Whatisthefunctionaldifferencebetween74ls138decoderand74ls148?74ls138isa3-8wiredecoder/multiplexer,74ls148isan8-3wireoctalpriorityencoder.Oneisdecodingandtheotherisencoding.OppositeeffectWhatsthedifferencebetween74LS138Dand74LS138N?Thosetwoarethesamechip,DisSOPpackage,NisDIPpackage.Whataretheoutputcharacteristicsof74LS138decoder?UnderthepremisethattheenableterminalsS1(activehigh),S2(activelow),andS3(activelow)arevalidatthesametime,onlyoneoutputterminalislowatatime(therestarehigh);Iftheenableterminalisinvalid,theoutputisallhighlevel.Whatdothelettersandnumbersin74ls138standfor?74ls138isa3-8-linedecoder.Thenumber74representsthe74seriesofthe54/74series,andthe74serieshasanoperatingtemperatureof0degreesto70degrees.LSisaseries,representingthelow-powerSchottkyseries.138isthevarietycode.Whatstheworkingprincipleof74ls138?74LS138workingprinciple①Whenonestrobeterminal(E1)ishighlevel,andtheothertwostrobeterminals(E2)and(E3)arelowlevel,attheoutputterminalscorrespondingtoY0toY7,thebinarycodeofaddressterminals(A0,A1,A2)canbedecodedatlowlevel.Forexample:whenA2A1A0=110,theY6outputterminaloutputsalow-levelsignal.②UsingE1,E2andE3,itcanbecascadedtoexpandintoa24-linedecoder;ifanexternalinverterisconnected,itcanalsobecascadedtoexpandintoa32-linedecoder.③Ifoneofthestrobeterminalsisusedasadatainputterminal,74LS138canalsobeusedasadatadistributor.④Itcanbeusedin8086decodingcircuittoexpandmemory.I.IntroductionTheheartrateisakeyindicatorvaluereflectingthehealthofthebody.Simplyput,theheartratereferstothefrequencyofcardiovascularbeatswithin1minute.Thetestofheartratecanshowscientificevidenceinworksuchasdiseasediagnosis,patientcare,andathletetraining.Inrecentyears,manymedicalequipmentandfitnessequipmentdevelopedandmanufacturedbycountriesaroundtheworldhaveadoptedheartratetestpowercircuits.Thelowcostofproductdevelopmentandhighperformanceheartratetestpowercircuitshaveimportantapplicationvalues.ThearticleintroducesthiskindofheartbeatratedetectionsystembasedonAD620integratedICindetail.Usingtheexcellentlow-noisecharacteristicsofAD620integratedIC,pluseffectivefilteringandamplifyingcircuits,combinedwithmicroprocessorsolutions,ahigh-precisionheartratemonitoringsystemisobtained.Figure1AD620CatalogI.IntroductionII.AD620ChipIII.CircuitDesign3.1BlockDiagram3.2SignalExtractionCircuitBasedonAD6203.3FilterAmplifierCircuit3.4MicroprocessorCircuit3.5ExperimentalResultsandDiscussionIV.ConclusionFAQOrdering&QuantityII.AD620chipAD620isalow-cost,high-precisioninstrumentationamplifier.Itonlyneedsanexternalresistortosetthegain,andthegainrangeis1to10000.Inaddition,AD620adopts8-pinSOICandDIPpackage,thesizeissmallerthanthediscretecircuitdesign,andthepowerconsumptionislower,soitisverysuitableforbattery-poweredandportableapplications.Itscharacteristicsareasfollows:EASYTOUSEGainSetwithOneExternalResistor(GainRange1to10,000)WidePowerSupplyRange(2.3Vto18V)HigherPerformancethanThreeOpAmpIADesignsAvailablein8-LeadDIPandSOICPackagingLowPower,1.3mAmaxSupplyLOWNOISE9nV/Hz,@1kHz,InputVoltageNoise0.28Vp-pNoise(0.1Hzto10Hz)EXCELLENTDCPERFORMANCE(BGRADE)50Vmax,InputOffsetVoltage0.6V/Cmax,InputOffsetDrift1.0nAmax,InputBiasCurrent100dBminCommon-ModeRejectionRatio(G=10)EXCELLENTACSPECIFICATIONS120kHzBandwidth(G=100)15sSettlingTimeto0.01%III.CircuitDesign3.1BlockDiagramThesurfaceofthehumanskincontainshumanECG,EMG,andpowerfrequencysignals.Generally,thenoiseoftheECGsignalcontainingheartrateinformationismuchsmallerthanthatofthepowerfrequencysignal.InordertoextracttheweakECGsignal,alow-noiseoperationalamplifiermustbeusedandareasonablefilteramplifiercircuitmustbedesigned.Figure2isablockdiagramoftheheartratedetectionsystem.Thewholeheartratedetectionsystemconsistsoffourparts:thesensorheadincontactwiththehumanskinsurface,thesignalextractioncircuit,thefilteramplifiercircuitandthemicroprocessorcircuit.Thesensorheadisgenerallyametalthatiseasytoconductelectricity.Aftercontactingthesurfaceofthehumanskin,ithascomplexelectricalsignalssuchashumanECGsignals,electromyographicsignals,andpowerfrequencysignals.Weusethelow-noiseAD620operationalamplifierasthecorechipoftheheartbeatrateextractioncircuit.Inthefilteringandamplifyingcircuitpart,asimplelow-passfilteringcircuitisused.Theexperimentalresultsshowthatthisfilteringcircuitissufficienttoextracttheheartratesignal.Afterfilteringtheamplifiedsignal,anadjustablecomparatorcombinedwithatransistorcircuitisusedtoforma5voltTTLlevelsignal,andfinallyconnectedtothemicroprocessor,theheartbeatsignalisprocessedbythemicrocomputer,andtheheartbeatrateiscalculatedanddisplayed.Figure2Blockdiagramofheartratedetectionprinciple3.2SignalExtractionCircuitBasedonAD620AD620operationalamplifier,usuallyusedinhigh-precisiontestinstruments,themaximumnonlinearerrorof40ppm,themaximumvoltageoffsetof50uV,themaximumtemperaturedriftof0.6uV/℃,becauseofitslownoise,lowbiascurrent,lowpowerconsumptioncharacteristics,itItiswidelyusedinmedicalfieldssuchaselectrocardiogram(ECG)andbloodpressuremonitoring.Figure3isasignalextractioncircuitbasedonAD620,inwhichtheLEFT_ARM,RIGHT_ARM,LEGthreeleadsareconnectedtothealuminumsheet(iethesensorhead),whicharerespectivelyconnectedtotheleftandrighthandsandrightfeetofthehumanbody.OurexperimentalresearchresultsshowthattheR4gainofLEFT_ARMis1K,thecorrespondingAD620operationalamplifiergainis50.Toomuchgainwillweakenthefinalsignal-to-noiseratio,sotheR4resistancevalueshouldbesetreasonablyintheexperiment.The0.1uFcapacitancebetweentheLEFT_ARMandRIGHT_ARMleadsistoeffectivelyweakenthepowerfrequencynoise.TheLEGleadisconnectedtoAD620throughTL082A,whichprovidesthereferencepotentialofthehumanbodyforthedifferentialsignalofLEFT_ARMandRIGHT_ARM.Figure3SignalextractioncircuitbasedonAD6203.3FilterAmplifierCircuitFigure4isafilteramplifiercircuit.Threeoperationalamplifiersconstituteathree-stageamplification,eachamplifying100times.Duetocircuitloss,especiallythelossoftheisolationcapacitor,theactualsignalamplificationislessthan1milliontimes.TheratiooftheresistancevaluesofR6andR5,R9andR8,R11andR10inthecircuitdeterminesthemagnificationfactor,andtheseresistancevaluesshouldbeadjustedreasonablyinpracticalapplications.Alow-passfiltercircuitshouldbeusedwhileamplifyingthesignaltoachievetheeffectoffilteringpowerfrequencynoise.Sincethefrequencyofthepowerfrequencynoiseis50Hz,thedesignedfiltercircuithasapassbandbandwidthoflessthan50Hz,thatis,theRCtimeconstantofthecapacitorresistormustbeofthesameorderofmagnitudeasthepowerfrequencysignalperiod.R7andC10inthecircuitformalow-passfilter.Weuse1uFcapacitorisolationbetweenlevelsofamplification.Thesecapacitorswillattenuatethesignalatthesametime,andthethreeoperationalamplifiersareselectedforsignalamplification,sothesignal-to-noiseratioisimproved.Itshouldbepointedoutthatiftheisolationcapacitoristoolarge,itiseasytocausetheoutputelectricalsignaltodrift.Figure4FilteramplifiercircuitFigure5istheshapingcircuit.Theheartbeatratesignalandsignal-to-noiseratioofthe2ND_OUTleadarelargeenough(thepulserateoftheheartbeatrateis1~5V),afterthehalf-waveshapingofD1,thentheadjustablecomparator,andfinallythetransistorQ1isconvertedtothemicrocontrollerlevel.Figure5Shapingcircuit3.4MicroprocessorCircuitThefinalsignalisprocessedbyAT89C51,andtheheartrateisdisplayedbyLEDdigitaltube.ThemicroprocessorcircuitwithAT89C51asthecoreisverymature,soitsnoneedtorepeathere.3.5ExperimentalResultsandDiscussionFigure6showstheactualmeasurementresultsofthehumanheartrateusingtheabovesystem.Figure6(a)isthevoltagesignalafterthesignal2ND_OUTisshapedbyD1.ItcanbeseenfromthefigurethatthisisactuallyacompleteECGsignal.Inacycleofsignals,therearetwomoreobviouspulsesignals.Thispulsecharacteristicvariesfrompersontoperson.ItisfoundthatthereisatleastonepulsesignalthroughactualmeasurementoftheECGsignalsofdifferentpeople.Figure6(b)showstheelectricalsignalofHEART_PULSE,whichisobtainedafterthesignalofFigure6(a)passesthroughthecomparatorandthetransistorswitch.Thesignalcanbedirectlyinputtotheportofthemicroprocessor,andthemicroprocessorcalculatesandoutputstheheartrate.Figure6HeartratesignaldiagramWhendevelopingtheabove-mentionedheartratedetectionsystem,thereareseveralkeypointstopayspecialattentionto:(1)ConnectingcapacitorstoLEFT_ARMandRIGHT_ARMcangreatlyimprovethesignal-to-noiseratio;themainenergyoftheheartratesignalonLEFT_ARMandRIGHT_ARMisatafrequencyofabout1Hz,andthecapacitorisalow-passfilterthatcanfilterandsuppressnoise;Choosealargecapacitortoeliminatehigh-frequencynoise.Intheexperiment,a10uFnon-polarcapacitorisused,andtheeffectisverygood;(2)Thelow-passfiltercircuiteffectivelyweakensthepowerfrequencysignalandimprovesthesignal-to-noiseratio;itadoptsacombinationofactivefilteringandpassivefilteringtofilterwhileamplifying,whichhasabettereffectthanfilteringafteramplification;(3)Capacitorisolationattenuationandmulti-stageamplificationarebeneficialtoimprovethesignal-to-noiseratio;themainnoiseis50Hzpowerfrequencysignals.Althoughthemulti-stageamplificationandfilteringincreasethermalnoise,ithasgreatsuppressionofpowerfrequencynoise.Ofcourse,thenumberofamplificationstagescannotbeinfinite,andthebestnumberofstagesistheminimumsumofpowerfrequencynoiseandthermalnoise;(4)SmallcapacitorisolationshouldbeusedtosuppressDCsignaldrift.Thisisshownbytheexperimentalresults,andthereasonneedstobefurtherstudied.IV.ConclusionThisarticlediscussesaschemebasedonAD620chipheartratedetection,andintroducesthecircuitdesignofthesensorhead,signalextraction,filteramplificationandmicroprocessorthatmakeupthesystem.Givesthemethodtoimprovethesystemperformance.ExperimentsshowthatthesystemcanobtainbetterECGsignalsandaccurateheartrate.Theheartbeatratedetectionsysteminthisarticlehasstronganti-interferenceability,simplestructureandlowcost.FAQWhatisAD620?AD620isalow-cost,high-precisioninstrumentationamplifier.Itonlyrequiresanexternalresistortosetthegain.Thegainrangeis1to10,000.CanIchangeAD620toAD623whenmakingMCUproducts?BothAD620andAD623aresingleinstrumentationamplifiers,andthepinarrangementisexactlythesame.Themaindifferenceis:AD620mustusepositiveandnegativepowersupplies,AD623canbeapositiveandnegativepowersupplyorasinglepowersupply.IftheoriginalboardisAD620,youcanreplaceitwith623;iftheoriginalboardisAD623,youmaynotbeabletoreplaceitwith620(itdependsonwhetherthepowersupplyoftheoriginalboardcircuitisdualpowersupplyorsinglepowersupply).AfterreplacingAD620andAD623insingle-chipproducts,theprogramcanworknormallywithoutmodification.WhatisthedifferencebetweenAD620BRandAD620AN?Theirpackagesaredifferent.WhatistheoutputresistanceofAD620?Howtoadjustit?AD620isakindoflowpowerconsumptioninstrumentamplifier,itsoutputresistanceisabout10K,thisistheinherentcharacteristicofthischip,generallyitisdifficulttoadjust.Ifyouhaverequirementsforoutputresistance,youcangenerallyuseanexternalcircuittosolveit.IsAD620apositivephaseamplificationorareversephaseamplification?AD620isaninstrumentamplifier,theoutputvoltageis[(Vin+)-(Vin-)]*gain.Ifthedesiredsignalis(Vin+)-(Vin-),thegainispositive,whichisequivalenttopositiveamplification.Conversely,ifthedesiredsignalis(Vin-)-(Vin+),thegainisequivalenttonegative,whichisequivalenttoreverseamplification.Whatisaninstrumentationamplifier?Instrumentationamplifier,animprovementofthedifferentialamplifier,hasaninputbuffer,doesnotrequireinputimpedancematching,sothattheamplifierissuitableformeasurementandelectronicinstruments

IRLU120PBF-VISHAY

I.IntroductionTheamplificationofweaksignalshashighrequirementsandhighdifficulty.Thesignalamplificationisrelatedtotherequirementsofstabilityandaccuracyofsignalamplification.Differentialamplificationtechnologyhasthecharacteristicsofsuppressingcommonmodesignalsandonlyamplifyingdifferentialmodesignalswithhighgain,soitisappliedtosmallsignalamplificationtechnology.ThesystemdesignadoptstheAD620chipwithdifferentialamplificationfunctiontoamplifytheweakvoltagesignalofthestrainsensortoachievethehighprecisionrequirementsofthesystem.Thisarticleusesvirtualinstrumenttechnologytocollectandanalyzetheamplifiedsignal,andwritethecorrespondingdisplayinterface.Themeasurementdataisanalyzedbythesecond-orderinterpolationmethodtoverifytheaccuracyofthecircuit.AD620CatalogI.IntroductionII.SystemDesignIII.SystemHardwareCircuitDesign3.1PressureMeasurementCircuit3.2VoltageSignalAmplifierCircuit3.3ReferenceVoltageSourceCircuitandVoltageZeroingCircuit3.4Voltage-currentConversionCircuitIV.TheOverallSoftwareDesignoftheSystemV.QuantitativeTestingandResultAnalysis5.1DataProcessingMethod5.2DataProcessingResults5.3ErrorAnalysisVI.ConclusionFAQOrdering&QuantityII.SystemDesignThesystemisprovidedwithtwovoltagesof12Vand5VfromaDCstabilizedsource.Whensetting12Vpowersupply,thesystemvoltageoutputfullrangeis5V,andthesensorwithstandsstaticpressurefullrangeis19.6N.Whenmeasuringwithinthefull-scalerange,themaximumabsoluteerrorofthestaticpressuresignalis9.810-3N,andtherelativeerroris0.02%.Theoutputsignaloftheloadcellprovidestwooutputmodes:voltageoutputandcurrentoutputaftertheamplifiercircuit.III.SystemHardwareCircuitDesignTheoveralldesignprocessofthesystemisshowninFigure1.ThesystemhardwarecircuitismainlycomposedofLC7012loadcell,AD620instrumentationamplifier,referencevoltagesource,voltagezeroingcircuit,signalfilteringandshapingcircuitandvoltage-currentconversioncircuit.Figure1Systemhardwarecircuitoveralldesignprocess3.1PressureMeasurementCircuitPressuremeasurementadoptsLC7012loadcell,withfullbridgemeasurementcircuit.LC7012loadcellhasthefollowingtwocharacteristicswhensubjectedtopressure:(1)Underthesamepressure,thestrainofthesensorstraingaugeandtheoutputvoltageofthebridgeareconstantandhavenothingtodowiththeprecisepositionofthepressureactingontheloadendofthesensor.(2)Theoutputvoltageandpressureofthefullbridgecircuitcomposedofstraingaugesarebasicallylinear.The4piecesofresistancestraingaugesintheLC7012loadcellareattachedtothestrainzoneofthedouble-holebeam.Whenthereisstaticpressure,thedouble-holebeamproducesquadrilateraldeformationundertheactionofthepressureandthesupportingforceofthesystemchassisonthedouble-holebeam.Thefourstraingaugesareconnectedtoafullbridgecircuitinafullbridgemode.Undertheexcitationofthebridgevoltage,differentweakvoltagesignalsareoutputwithdifferentpressures,andtheamplifiercircuitamplifiestheweakvoltagesignalssentbythebridge.Thefull-bridgeequal-armbridgehassimplestructure,strongsymmetry,highsensitivity,andgoodconsistencyoftheparametersofeacharm.Theeffectsofvariousinterferencescancanceleachother,forexample,itcansuppresstheeffectsoftemperaturechangesandsuppresstheinterferenceoflateralforces.Itiseasiertosolvetheproblemofcompensationoftheloadcell.Thefull-bridgemeasurementcircuitenablestheoutputoftheweakvoltagesignaltoeliminateerrorscausedbythecircuititselfasmuchaspossible,andprovidestheinitialguaranteefortheoverallaccuracyofthesystem.3.2VoltageSignalAmplifierCircuitInordertoimprovetheamplificationaccuracyoftheweakvoltagesignaloutputbythebridge,thesignalamplifyingcircuitselectstheAD620chipproducedbyADIasthecoreelement,anddesignsaspecialadjustablereferencevoltagesourceforittomeetthereferencevoltagerequirementsofdifferentvoltagesources.Andtheneedtoaccuratelyamplifyweaksignals.Figure2AD620PinoutAD620isalow-cost,high-precisioninstrumentationamplifier.Itonlyneedsanexternalresistortosetthegain.Thegainrangeis1to10000dB.AndAD620powerconsumptionislow,themaximumoperatingcurrentis1.3mA.AD620hasthecharacteristicsofhighprecision(maximumlinearity4010-6),lowoffsetvoltage(maximum50V)andlowoffsetdrift(maximum0.6V/℃),makingitanidealchoiceforprecisiondataacquisitionsystemssuchassensorinterfaces.Figure2showsitspinarrangement.AD620monolithicstructureandlasercrystaladjustmentallowcircuitcomponentstobecloselymatchedandtracked,thusensuringtheinherenthighperformanceofthecircuit.AD620isathree-op-ampintegratedinstrumentationamplifierstructure,inordertoprotectthehighprecisionofgaincontrol,theinputtransistorprovidesdifferentialbipolarinput,andusesprocesstoobtainlowerinputbiascurrent,throughthefeedbackoftheinputstageinternalop-amp,Keepthecollectorcurrentoftheinputtransistorconstant,andaddtheinputvoltagetotheexternalgaincontrolresistorRG.AD620internalgainresistanceisadjustedtoanabsolutevalueof24.7k,soanexternalresistancecanbeusedtoachievepreciseprogrammingofthegain.ThegainformulaisThevoltagesignalamplifiedbytheAD620canpassthroughafilteringandshapingcircuitandbedisplayedindigitalformwithadigitaltubethroughtheanalog-to-digitalconvertermodule.Inordertofullyutilizeanddemonstratethefunctionsofvirtualinstruments,thesystemusesLabVIEWtodesignthecorrespondingsignalacquisitionandprocessingprogramanddisplayinterface.3.3ReferenceVoltageSourceCircuitandVoltageZeroingCircuitThereferencevoltagesourcecircuitismainlycomposedofaZenerdiodeLM285,alow-powerdualoperationalamplifierchipLM258,avariableresistorandanumberoffixedresistanceresistors,asshowninthelowerleftpartofFigure3.ThisreferencevoltagesourcecircuitcanprovideAD620with1.25Vor2.5Vaccuratereferencevoltage.Figure3VoltagesignalamplifiercircuitThevoltagestabilizingdiodeLM285providestheprimarystablevoltage,butthetemperaturedriftofthediodeislarge,andthevoltagestabilizationvalueofdifferentdiodesinthesamebatchisnotthesame,sothecorrespondingauxiliaryvoltagestabilizingcircuitmustbedesignedforit.TheoperationalamplifierLM258U1AamplifiesthevoltagefromtheZenerdiodeandfeedsbacktheoutputvoltagethroughthefeedbackresistorR2,makingtheoutputvoltagemorestable.ResistorR5andpotentiometerW1dividetheoutputvoltageoftheZenerdiode.PotentiometerW1hastwofunctions:(1)AdjustingW1canmakethevoltagefollowercomposedofoperationalamplifierLM258U1Bhavedifferentoutputvoltages,andthenprovidedifferentstablereferencevoltagestoAD620.(2)ThepotentiometerW1alsoplaysaroleofzeroadjustmentontheamplifyingcircuitcomposedofAD620.Thevoltagefollowerisusedbecausethevoltagefollowercanincreasetheinputimpedanceandreducetheoutputimpedance,andtherequirementofthepowersupplyisthatthecircuithasasmalleroutputresistance.AD620itselfhasaninternalzeroadjustmentfunction,butaccordingtoactualmeasurement,itisfoundthatwhenthedifferentialinputiszero,theoutputisnotzero,butaboutafewtenthsofmV.Therefore,inordertoimprovetheaccuracyoftheoutput,itisnecessarytoperformtheAD620Externalzeroadjustment,byprovidingdifferentreferencevoltagestotheAD620referencevoltagepins,theoutputvoltageoftheinstrumentationamplifierAD620canbezerowhenthedifferentialinputiszero.ThecircuitjustadjustsW1tomaketheoutputterminalofthevoltagefollowerhavedifferentvoltageoutput,adjuststhereferencevoltageofAD620,thusplaystheroleofzeroadjustmenttoAD620.TheinstabilityofthereferencevoltagewilldirectlyaffectthestabilityoftheamplifiercircuitcomposedofAD620,andleadtoinaccuracyofthefinaloutputresult.Therefore,thesystemdoesnotdirectlyusetherelativelystable-12Vor-5VprovidedbytheDCstabilizedsourceasthereferencevoltage.3.4Voltage-currentConversionCircuitThevoltage-currentconversioncircuitenablesthesystemtooutputintheformofcurrent.TheAD620iscombinedwithanAD705operationalamplifierandtworesistors(asshowninFigure4)toformaquietcurrentsource.AD705providesabufferforthereferencepin.Ensuregoodcommonmoderejection(CMR)performance.TheoutputvoltageofAD620appearsontheresistanceRL,thelatterconvertsitintoelectriccurrentoutput.Figure4Schematicdiagramofvoltage-currentconversioncircuitAD705isalow-power,bipolaroperationalamplifierwithabipolarfieldeffecttransistorinputstage.Therefore,ithasthecharacteristicsofhighinputimpedance,lowinputoffsetvoltage,smallinputbiascurrent,andsmallinputoffsetvoltagedrift.TheinputbiascurrenthasreachedthepAlevel.Itnotonlyhasmanyadvantagesofbipolarfieldeffecttransistorsandbipolaroperationalamplifiers,butalsoovercomesthedefectoflargebiascurrentdriftinthefulltemperaturerange.Inthefulltemperaturerange,thetypicalvalueofthebiascurrentofAD705onlyincreasesby5times,andthebiascurrentofthegeneralbipolarfieldeffecttransistoroperationalamplifierincreasesby1,000times.ComparedwithOP07,thetemperaturedriftvalueis1/2ofOP07,themaximuminputbiascurrentisonly1/5ofOP07,andtheinputoffsetvoltageisonly1/20ofOP07.Becauseitisabipolarfieldeffecttransistorinputpole,thesignalsourceimpedanceismuchhigherthanOP07,whileitsDCaccuracyremainsunchanged.IV.TheOverallSoftwareDesignoftheSystemThesystemsoftwareiswritteninLabVIEW.LabVIEWisagraphicalprogramminglanguage,whichiswidelyusedinvariousfieldsasastandardfordataacquisitionandinstrumentcontrolsoftware.LabVIEWisapowerfulandflexiblesoftware.Useittoeasilybuildyourownvirtualinstrument.Inthecaseofonepieceofhardware,differentfunctionsofdifferentinstrumentscanberealizedbychangingthesoftwareprogramming,whichisconvenientandfast.Combinedwiththenewdevelopmentdirectionofthecurrenttestingfieldinstruments,thefinaloutputanalogvoltagesignaliscollectedbyAdvantechsUSB4716universaldataacquisitionmoduleandtransmittedtothecomputer.UseNIvirtualinstrument(LabVIEW)todesignvoltagesignalacquisitioncontrolprogramandvoltagedatareal-timedisplayinterface.UseLabVIEWsoftwareplatformtoanalyzeandprocessthedigitalvoltagesignalfromUSB4716.ThepartprogramofLabVIEWvoltagesignalacquisitioncontrolanddisplayisshowninFigure5.Figure5VoltagesignalacquisitionprogramV.QuantitativeTestingandResultAnalysis5.1DataProcessingMethodSecond-orderinterpolation(parabolicinterpolation):select(x0,y0),(x1,y1),(x2,y2)correspondinginterpolationequationsfromasetofdata.5.2DataProcessingResultsInordertoobtainanaccuratecorrespondencebetweenpressureandvoltageandfacilitatesubsequentanalysisofabsoluteandrelativeerrors,theexperimentusesstaticmeasurementmethodstomeasureaseriesofstaticpressurevalues,andquantitativelyanalyzetheexperimentalresultstodeterminetheaccuracyofthecircuit.Commonlyusedwaveformtimedomainandfrequencydomainanalysismethods.Table1Brightness/ContrastComparisonPressure/N0...2.94...8.829.8...13.72...19.6219.6Voltage/V0...0.75...2.2472.498...3.498...4.755.001Measure20staticpressurevaluesfromsmalltolargewithinthefullscalerange,andmakethepressureincrement△thesame.Let△=0.98N,andusethesecond-orderinterpolationmethodtoanalyzetherelationshipbetweenvoltageandpressure.SelectthreerepresentativepointsfromTable1:(x0,y0)=(0,0);(x1,y1)=(2.498V,9.8N);(x2,y2):(5.001V,19.6N).Bringinsecond-orderinterpolationTherelationshipcurvebetweenthepressureonthesensorandthesystemoutputvoltageisY=(-1.56810-3)x2+3.927x(3)5.3ErrorAnalysisTheabsoluteerrorreflectsthedeviationofthemeasuredvaluefromthetruevalue,thatis,theabsolutevalueofthedifferencebetweenthemeasuredvalueandthetruevalue.Theabsoluteerrorcanbedefinedas:=|X-L|(4)Intheformula,istheabsoluteerror;Xisthemeasuredvalue;Listhetruevalue.Relativeerroristheratioofabsoluteerrortothemeasuredvalueortheaveragevalueofmultiplemeasurements,andtheresultisusuallyexpressedasapercentage,soitisalsocalledpercentageerror.Absoluteerrorcanindicatethereliabilityofameasurementresult,whilerelativeerrorcancomparethereliabilityofdifferentmeasurementresults.Whenmeasuringwiththesametool,thelargerthemeasuredvalue,thesmallertherelativeerrorofthemeasurementresult.TheabsoluteerrorandrelativeerrorofthestraingaugepressuresensortestsystemareshowninFigure6andFigure7.Thetwofiguresrespectivelyshowtheabsoluteerrorandrelativeerrorcurvesoftwootherdataprocessingmethods:linearinterpolationandaverageselectionmethod.ItcanbeseenfromFigure6andFigure7thatthecalculationaccuracyofthesecond-orderinterpolationmethodishigherthantheothertwomethods,whichalsoprovesthatthechoiceofthedataprocessingmethodiscorrect.Figure6AbsoluteerrorcurveFigure7RelativeerrorcurveVI.ConclusionKnownfromtherelativeerrorandabsoluteerrorgraphthat,themeasurementresulterrorofthecircuitintherangeof0~4.9Nisrelativelylarge,butitstillmeetsthesystemdesignrequirements.Afteranalyzingthesensorandtheexperimentalmeasurementcircuit,itisbelievedthatthereasonforthelargererrorcomesfromtherigidityofthecantileverbeammaterialofthesensorandtheflexibleinfluenceoftheviscousmaterialthatfixesthestraingauge.Becausetheaccuracyoftheweakvoltagesignaloutputbythebridgeisaffected,theerrorisalsoamplifiedafterpassingthroughtheamplifyingcircuit,resultinginalargererrorintheexperimentalresultwhenthemeasuredvalueissmall.Insummary,thepressuresignalamplificationsystemsatisfiesthedesignrequirementsofabsolutefull-scaleerror9.810-3Nandrelativeerror.FAQWhatisAD620?AD620isalow-cost,high-precisioninstrumentationamplifier.Itonlyrequiresanexternalresistortosetthegain.Thegainrangeis1to10,000.CanIchangeAD620toAD623whenmakingMCUproducts?BothAD620andAD623aresingleinstrumentationamplifiers,andthepinarrangementisexactlythesame.Themaindifferenceis:AD620mustusepositiveandnegativepowersupplies,AD623canbeapositiveandnegativepowersupplyorasinglepowersupply.IftheoriginalboardisAD620,youcanreplaceitwith623;iftheoriginalboardisAD623,youmaynotbeabletoreplaceitwith620(itdependsonwhetherthepowersupplyoftheoriginalboardcircuitisdualpowersupplyorsinglepowersupply).AfterreplacingAD620andAD623insingle-chipproducts,theprogramcanworknormallywithoutmodification.WhatisthedifferencebetweenAD620BRandAD620AN?Theirpackagesaredifferent.WhatistheoutputresistanceofAD620?Howtoadjustit?AD620isakindoflowpowerconsumptioninstrumentamplifier,itsoutputresistanceisabout10K,thisistheinherentcharacteristicofthischip,generallyitisdifficulttoadjust.Ifyouhaverequirementsforoutputresistance,youcangenerallyuseanexternalcircuittosolveit.IsAD620apositivephaseamplificationorareversephaseamplification?AD620isaninstrumentamplifier,theoutputvoltageis[(Vin+)-(Vin-)]*gain.Ifthedesiredsignalis(Vin+)-(Vin-),thegainispositive,whichisequivalenttopositiveamplification.Conversely,ifthedesiredsignalis(Vin-)-(Vin+),thegainisequivalenttonegative,whichisequivalenttoreverseamplification.Whatisaninstrumentationamplifier?Instrumentationamplifier,animprovementofthedifferentialamplifier,hasaninputbuffer,doesnotrequireinputimpedancematching,sothattheamplifierissuitableformeasurementandelectronicinstrumentsIDescriptionAD620isalow-power,high-precisioninstrumentationamplifier.BasedontheinformationprovidedbytheADcompany,thisblogintroducesthecharacteristicsandtypicalusageofAD620.Besides,thisblogalsointroducestheapplicationofAD620.Theapplicationsaremainlyaboutphotoelectricdetection,ultrasonictesting,etc.Figure1.AD620IDescriptionIIIntroductionIIIAD620PinoutandWorkingPrincipleIVAD620TypicalUsageVAD620Application5.1ApplicationinPhotoelectricDetection5.2ApplicationinUltrasonicTestingVIConclusionFAQOrdering&QuantityIIIntroductionAD620isalow-power,high-precisioninstrumentationamplifier.Anditcansettheamplificationfactorfrom1to1000withonlyanexternalresistor.Itissmallinsize,inan8-pinSOICorDIPpackage;thepowersupplyrangeis2.3V~18V;themaximumpowersupplycurrentisonly1.3mA.AD620hasgoodDCandACcharacteristics.Itsmaximuminputoffsetvoltageis50V,themaximuminputoffsetvoltagedriftis1V/℃,andthemaximuminputbiascurrentis2.0nA.WhenG=10,itscommon-moderejectionratioisgreaterthan93dB.Theinputvoltagenoiseisat1kHz,thepeak-to-peakvalueoftheinputvoltagenoiseis0.28Vintherangeof0.1Hz~10Hz,andtheinputcurrentnoiseisWhenG=1,itsgainbandwidthis120kHz,andthesettlingtimeis15s.Ingeneral,thecharacteristicsofAD620canbesummarizedasfollows:AD620canensuretheperformanceindicatorsrequiredforhigh-gainprecisionamplification.Forexample,lowoffsetvoltage,lowoffsetvoltagedrift,andlownoise,etc.;Withonlyoneexternalresistor,themagnificationcanbesetfrom1to1000;Smallsize,with8pins;Lowpowerconsumptionanditsmaximumsupplycurrentare1.3mA.IIIAD620PinoutandWorkingPrincipleThepinofAD620isshownasinFig.2,itsstructurediagramisshownasinFig.3.Figure2.AD620PinoutFigure3.AD620StructureDiagramAD620isamonolithicinstrumentamplifier.Itisdevelopedonthebasisoftheimprovementofthetraditionalthree-opamplifiercombination.TheinputtransistorsQ1andQ2providetheonlybipolardifferentialinput.Duetotheinternalsuperprocessing,itsinputoffsetcurrentis10timeslowerthannormal.ThroughthefeedbackoftheQ1-A1-R1loopandtheQ2-A2-R2loop,thecollectorcurrentsofQ1andQ2arekeptconstant.Thus,theinputvoltageisequivalenttothetwoendsoftheexternalresistorRg.AndthedifferentialamplificationfactorfromtheinputtotheA1/A2outputisG=(R1+R2)/Rg+1.TheunitygainsubtractorcomposedofA3eliminatesanycommon-modecomponents.Andthenitproducesasingle-channeloutputrelatedtothepotentialoftheREFpin.ThevalueofRgalsodeterminesthetransconductanceofthepreviousstageopamp.WhenRgdecreases,theamplificationfactorincreases.Andthetransconductancetotheinputtransistorgraduallyincreases.Thishasobviousadvantages:theincreaseintheamplificationfactorincreasestheopen-loopgain.Thus,theerrorrelatedtogainisreduced.Thegain-bandwidthproductdeterminedbyC1,C2andthepre-opamptransconductanceincreases.Thus,thefrequencyresponseisimproved.Theinputvoltagenoiseismainlydeterminedbythecollectorcurrentoftheinputtransistorandthebaseresistance.Andtheinputvoltagenoiseisreducedto.TheinternalgainresistorsR1andR2areaccuratelydeterminedas24.7k.Inthiscase,theoperationalamplifiergainisaccuratelydeterminedbyRg.G=49.4k/Rg+1orRg=49.4k/(G-1)IVAD620TypicalUsage(1)Theinputbiascurrentisthecurrentrequiredtobiastheinputtransistoroftheopamp,anditmusthaveareturnloop.Therefore,whenamplifyinganAC-coupledsignalsourcelikeatransformer,eachinputpointmusthaveaDCpathtoground.AsshowninFigure4-6.Figure4.BiasCurrentLoopwithTransformerCoupledInputFigure5.BiasCurrentLoopforThermocoupleInputFigure6.BiasCurrentLoopWhenACCoupledInput(2)Allinstrumentamplifiersrectifythesignaloutsidethechannel.Ifasmallsignalisamplified,thisrectifiedvoltagebecomesaDCoffsetvoltage.ThestructureofAD620allowsafirst-levelfiltertobeinsertedbetweenthebaseandemitteroftheinputtransistortofilteroutunwantedrectifiedsignals,asshowninFigure5.RC=1/2f,fisgreaterthanorequaltothebandwidthofAD620,C150pF.Figure7.PrimaryFilterPrincipleDiagram(3)TheoutputvoltageofAD620isrelatedtothereferenceterminal.ConnectingtheREFterminaltoanappropriategroundingpointcansolvemanygroundingproblems.Manydataacquisitionsystemsseparatetheanaloggroundfromthedigitalground.Howcome?Justaimingtoisolatethelow-levelanalogsignalfromthenoisydigitalenvironment.Thegroundingprincipleisasfollows:eachindependentgroundloopminimizesthecurrentflowingfromthesensitivepointtotheground.Thesegroundloopsmustbeconnectedtogetheratsomepoint,usuallyontheADC.LetstakealookatFigure7.Thereferenceterminal5oftheAD620,thegroundterminalofthesample-and-holdAD585.Andthegroundterminaloftheanalogpowersupplyarerespectivelyconnectedtotheanaloggroundterminaloftheanalog-to-digitalconverterAD574A.Thegroundterminalofthedigitalpowersupplyisconnectedwiththedigitalgroundoftheanalog-to-digitalconverterAD574A.Finally,theanaloggroundanddigitalgroundareconnectedtotheAD574A.Inmanyapplications,shieldedcablesareoftenusedtoreducenoiseinterferenceattheinput.Properdrivetotheshieldcanreducethedifferentialphaseshiftcausedbycablecapacitanceandstraycapacitance.AndensurethattheACcommon-moderejectionratiodoesnotdrop.Figure8showsthedifferentialshielddriveconnection.Figure9showsthecommon-modeshielddriveconnection.Figure8.DifferentialShieldDriveFigure9.CommonModeShieldDriveVAD620Application5.1ApplicationinPhotoelectricDetectionPhotoelectricdetectioniswidelyusedintheindustry.Theprincipleofdesigningaphotoelectricdetectionsystemistoreducethetotalsystemnoisetoaminimum.Thenoiseofthesystemmainlyincludesdetectornoise,resistancenoise,andoperationalamplifiernoise.Becausetheyareindependentofeachother,thetotalnoisecanbeexpressedasUn(T)=[Un2(D)+Un2(L,F)+Un2(A)]1/2Intheformula:Un2(D)Detectornoisevarieswithdifferentphotodetectors.Theappropriatedetectorshouldbeselectedaccordingtothesystemrequirements;Un2(L,F)Loadresistancenoise;Un2(A)Opampnoise.ThenoiseofAD620isverysmall.Therefore,itisoftenusedasthepre-opamplifierofthephotoelectricdetectioncircuit.Takethephotodiodeasthedetectorasanexampletoillustrate.Here,supposethecurrentofthephotodiodeisID,thenID=ISC+IdarkIntheformula:ISCPhotocurrent.Itisproportionaltothelightintensity,whichistheeffectiveinformationdetected;IdarkDarkcurrent.ItconsistsofthecurrentonthesurfaceofthediodeandtheusualPNjunctioncurrent.Itbelongstoinvalidinformationinthesystem.Weneedtoeliminatetheinfluenceofdarkcurrent.TwodiodesD1andD2withthesameperformanceandtworesistorsR1andR2withtheresistancevalueofRareselectedtoformabridge.AsshowninFigure10.Figure10.PhotoelectricDetectionPreamplifierCircuitWhenD1haslightandD2hasnolight,theinputvoltageatbothendsoftheop-ampis(ISC+Idark)-R1-Idark-R=ISC-R1.Itisonlyrelatedtothephotocurrent,thuseliminatingtheinfluenceofthedarkcurrent.5.2ApplicationinUltrasonicTestingInthefieldofultrasonictesting,especiallywhenultrasonicwavespropagateinanon-uniformandattenuatedmedium,theechoafterencounteringtheinterfaceisveryweak.Ifageneralop-ampisusedforpre-processing,thenoiseisoftenlargeandeffectivesignalscannotbeobtained.ChoosingAD620asthepre-amplifiercircuithasasimpleconnectionandlownoise.AsshowninFigure11.Figure11.UltrasonicDetectionReceivingFrontCircuitVIConclusionAD620isahighprecisioninstrumentationamplifier.Intheapplication,wealsoneedtopayattentiontopreventtheblockageoftheamplifier.IfastrongDCsignalissuperimposedontheweaksignal,wemustsetupaseparationcircuit.Inthisway,theDCsignalcanbeseparated.FAQWhatisAD620?AD620isalow-cost,high-precisioninstrumentationamplifier.Itonlyrequiresanexternalresistortosetthegain.Thegainrangeis1to10,000.CanIchangeAD620toAD623whenmakingMCUproducts?BothAD620andAD623aresingleinstrumentationamplifiers,andthepinarrangementisexactlythesame.Themaindifferenceis:AD620mustusepositiveandnegativepowersupplies,AD623canbeapositiveandnegativepowersupplyorasinglepowersupply.IftheoriginalboardisAD620,youcanreplaceitwith623;iftheoriginalboardisAD623,youmaynotbeabletoreplaceitwith620(itdependsonwhetherthepowersupplyoftheoriginalboardcircuitisdualpowersupplyorsinglepowersupply).AfterreplacingAD620andAD623insingle-chipproducts,theprogramcanworknormallywithoutmodification.WhatisthedifferencebetweenAD620BRandAD620AN?Theirpackagesaredifferent.WhatistheoutputresistanceofAD620?Howtoadjustit?AD620isakindoflowpowerconsumptioninstrumentamplifier,itsoutputresistanceisabout10K,thisistheinherentcharacteristicofthischip,generallyitisdifficulttoadjust.Ifyouhaverequirementsforoutputresistance,youcangenerallyuseanexternalcircuittosolveit.IsAD620apositivephaseamplificationorareversephaseamplification?AD620isaninstrumentamplifier,theoutputvoltageis[(Vin+)-(Vin-)]*gain.Ifthedesiredsignalis(Vin+)-(Vin-),thegainispositive,whichisequivalenttopositiveamplification.Conversely,ifthedesiredsignalis(Vin-)-(Vin+),thegainisequivalenttonegative,whichisequivalenttoreverseamplification.Whatisaninstrumentationamplifier?Instrumentationamplifier,animprovementofthedifferentialamplifier,hasaninputbuffer,doesnotrequireinputimpedancematching,sothattheamplifierissuitableformeasurementandelectronicinstrumentsIIntroductionHere,youcanlearnabouttheAD620instrumentamplifiercircuit.Besides,youcanalsobrowseAD620mainfeatures,workingprinciples,andapplications.Thisbloggenerallydiscussesthefollowing3basicquestions:1.Whatisaninstrumentationamplifier;2.Howdoesitwork;3.Howandwheretouse.Figure1.AD620CatalogIIntroductionIIDescriptionIIIAD620TechnicalIndicatorsIVAD620WorkingPrincipleVAD620ApplicationVIConclusionFAQOrdering&QuantityIIDescriptionOperationalamplifiershaveevolvedoverthedecadesandasaresult,thereisawidevarietyofthem.Theycanbeeasilycategorizedaccordingtotheirapplicationrequirements.Themaincategoriesincludegeneral-purpose,low-voltage,low-power,high-speed,andhigh-precisiontypes.Inrecentyears,applicationssuchasconsumerelectronics,communication,andnetworkinghavebeendevelopingcontinuously.Andtheseconstantlydevelopingindustriesalsoputforwardnewtechnicalrequirementsforop-ampproducts.AD620instrumentamplifieristheproductofADcompany.Duetoitssupertechnology,AD620hasthefollowingcharacteristics:1.3mAMaximumWorkingCurrent5VInputOffsetVoltage1V/℃InputOffsetDriftMaximum93dBCommonModeRejectionRatioAdjustableGainRangeEasytoAdjustandLowNoise.AndwhycanAD620becomeanindustry-standardhigh-performance,low-costinstrumentationamplifier?ThatsbecausethecoreofAD620isathree-stageop-ampcircuit,whichhasahighcommon-moderejectionratio,goodtemperaturestability,wideamplificationband,andlownoise.Andithasthecharacteristicsofhighaccuracy,easyuse,andlownoise.sothisisalsothereasonwhyAD620canbesopopular.IIIAD620TechnicalIndicatorsThemaintechnicalindicatorsofAD620areasfollows:Bandwidth800MHzOutputpower2.4mWPowergain120dBWorkingvoltage15VStaticpowerconsumption0.48mWInoltage60VConversionrate1.2V/SPackageformDIP8Operatingtemperaturerange-55℃~+125℃IVAD620WorkingPrincipleThefunctionalstructureoftheAD620amplifierisshowninFig.2.Figure2.AD620FunctionalBlockDiagramDoyouknowwhatthecharacteristicsofthisamplifierare?Theansweris:differentialinput,asingle-endedoutput.ThevoltagegaincanbedeterminedbyaresistorRG.Thegainsareadjustable,whichsolvestheproblemofconnectingthesubsequentloadtotheground.Besides,A1andA2formadifferentialinputandadifferentialoutputwithin-phasehighinputimpedanceandundertakeallgainamplificationtasks.Becausethecircuitstructureissymmetrical,whichmeanswhenthegainchanges,theinputimpedancedoesnotchange.ThefeedbackresistanceRl=R2=24.7k.Thecommon-modegain,offset,drift,andothererrorsoftheamplifiersA1andA2aremutuallycompensated.ThegainofthelatterstageA3is1,whichhasahighercommon-moderejectionratioandanti-interferenceability.AD620isamonolithicintegratedamplifier.Anditisdevelopedonthebasisoftheimprovementofthetraditionalthree-opamplifiercombination.AsshowninFigure2,theinputtransistorsQ1andQ2providetheonlybipolardifferentialinput.Duetotheinternalultra-processing,itsinputoffsetcurrentis10timeslowerthanthegeneralcase.ThroughthefeedbackoftheQ1-A1-R1loopandtheQ2-A2-R2loop,theintegratedpolecurrentofQ1andQ2iskeptconstant.SotheinputvoltageisequivalenttothetwoendsoftheexternalresistorRG.ThedifferentialamplificationfactorfrominputtoA1/A2outputisG=(R1+R2)/RG+1.TheunitygainsubtractorcomposedofA3eliminatesanycommon-modecomponents.Thereby,itproducesasingle-channeloutputrelatedtothepotentialoftheREFpin.Figure3.AD620SowhataboutRG?ThevalueofRGalsodeterminesthetransconductanceofthepreviousstageop-amp.WhenRGdecreases,themagnificationincreases.WhenRGdecreases,thetransconductancetotheinputtransistorgraduallyincreases.Thishasthefollowingtwoobviousadvantages:First,theincreaseintheamplificationfactorincreasestheopen-loopgain.Therebyreducingthegain-bandwidthproductandincreasingthefrequencyresponse;Second,itismainlydeterminedbytheinputtransistorcollectorcurrentandbaseresistance.ByaccuratelycorrectingthevalueoftheinternalgainresistorsR1andR2to24.7k,wecanmaketheoperationalamplifiergain(derivedbycalculation)accuratelydeterminedbyRG:G=49.4k/RG+1orRG=49.4k/(G-1)Figure4.AD620CircuitStructureDiagramRGistheexternalgainadjustment.Tomeettherequiredamplificationfactor,wecanconnectthishigh-precisionresistancebetweenpin1and8.ByusingtheamplifierAD620,thegainerrorcanbelessthan0.01%,andthenon-linearityislessthan0.002%.Fromtheapplicationpointofview,AD620isparticularlysuitableforapplications.Suchassensorinterface,ECGmonitor,precisionvoltagecurrentconversionandotherapplications.Ifweanalyzethecircuittechnologyperformance,wewilladeeperunderstandingofAD620.Thatis,AD620isactuallyalow-power,high-precisioninstrument,broadbandintegratedoperationalamplifier.VAD620ApplicationInstrumentationamplifiersaresometimesmisunderstoodbypeople.Here,weneedtopointout2ideas:First,notallamplifiersusedforinstrumentationareinstrumentationamplifiers;Second,allinstrumentationamplifiersarebynomeansonlyusedforinstrumentation.Instrumentationamplifiersareusedinmanyfields.Frommotorcontroltodataacquisitionandautomotivesystems.Instrumentationamplifierisaclosed-loopgainunit.Andwithdifferentialinputandsingle-endedoutputrelativetothereferenceend.Inmostcases,theimpedanceofthetwoinputendsoftheinstrumentationamplifierisbalanced.Theresistanceisveryhigh,anditstypicalvalueis109.Theinputbiascurrentisalsoverylow,typically1nAto50nA.Liketheoperationalamplifier,itsoutputimpedanceisverylow,usuallyonlyafewmilliohmsinthelowfrequencyrange.Theclosed-loopgainofanoperationalamplifierisdeterminedbytheexternalresistance.Theexternalresistanceisconnectedbetweenitsinvertinginputandoutput.Therearedifferencesbetweentheinstrumentamplifierandtheamplifier.Theinstrumentamplifierusesaninternalfeedbackresistornetwork,whichisisolatedfromitssignalinput.Toapplyinputsignalstothetwodifferentialinputterminalsoftheinstrumentationamplifier.Thegaincaneitherbepresetinternallyorsetbytheuser.Throughapinconnectedtoaninternalorexternalgainresistor,whichisalsoisolatedfromthesignalinputterminal.Figure5showsablockdiagramofadifferentialamplifier.Figure5.DifferentialAmplifierICThistypeofICisaspecial-purposeinstrumentationamplifier.Anditwhichusuallyconsistsofasubtractoramplifierfollowedbyanoutputbuffer(perhapsone-stagegain).ThefourresistorsusedforthesubtractorareusuallyinsidetheIC,sotheycanbepreciselymatchedtoachieveahigherCMR.Manydifferentialamplifiersaresuitableforapplications.Wherethecommon-modevoltageandsignalvoltagemayeasilyexceedthesupplyvoltage.Thesedifferentialamplifiersusuallyusehigh-valueinputresistorstoattenuatethesignal.Generallyspeaking,instrumentationamplifiersanddifferentialamplifiersareusedinthefollowingranges:DataAcquisitionThemainpurposeoftheinstrumentationamplifieristoamplifytheweaksignaloutputbythesensorinanoisyenvironment.Amplificationofsignalsfrompressuresensorsortemperaturesensorsiscommon.Commonbridgeapplicationsincludestrainforceandweightmeasurement.MedicalInstrumentsInstrumentationamplifiersarewidelyusedinmedicalequipment.Suchaselectrocardiographsandelectroencephalographs,bloodpressuremonitors,anddefibrillators.Thedifferentialamplifierofmonitoringandcontrolelectronicscanbeusedtomonitorthevoltageandcurrentinthesystemandtriggerthealarmsystemwhenthenormalvalueisexceeded.Becausedifferentialamplifiershavetheabilitytosuppresshighcommon-modevoltages,theyareoftenusedinsuchapplications.Figure6.ElectrocardiographSoftwareProgrammableApplicationsToallowsoftwaretocontrolthehardwaresystem,wecanturntoinstrumentationamplifiers.Instrumentationamplifierscanbeusedonchipswithsoftwareprogrammableresistors.AudioApplicationsBecauseinstrumentationamplifiershavehighCMR,theyareusedforaudio(e.g.microphonepreamplifiers)toextractweaksignalsinnoisyenvironments.Also,itcanbeusedtominimizetheoffsetcausedbygroundloopsVoltageandnoise.High-speedSignalConditioningDuetotheincreasedspeedandaccuracyrequirementsoftodaysvideodataacquisitionsystems,thedemandforbroadbandinstrumentationamplifiersisincreasing.EspeciallyinthefieldofCCDimagingequipmentthatrequiresoffsetcorrectionandinputbuffering.Inthisfield,doublecorrectionsamplingtechnologyisusuallyusedtocorrecttheCCDimage.Generallyusetwosample-and-holdamplifierstomonitortheimageandreferencelevel,andsendthesignalvoltagetoaninstrumentationamplifiertoprovideaDCcorrectionoutput.Figure7.CCDCameraVideoApplicationsHigh-speedinstrumentationamplifiersareusedinmanyvideoandcableradiofrequency(RF)systemstoamplifyorprocesshigh-frequencysignals.PowerControlApplicationsInstrumentationamplifierscanalsomonitorthemotor(monitoringandcontrollingthemotorsspeed,torque,etc.)bymeasuringthemotorsvoltage,currentandthephaserelationshipofthethree-phaseACmotor.Thedifferentialamplifierisusedwhentheinputsignalvoltageexceedsthepowersupplyvoltage.VIConcusionGenerallyspeaking,high-speedoperationalamplifiersaremainlyusedincommunicationequipment,videosystems,andtestandmeasurementinstruments.Advancedapplicationsintestandmeasurement,communications,medical,imagingandotherfieldsarethemaindrivingforcestoimproveamplifierperformance;DSLandconsumervideoapplicationsareitslargestmarkets.FAQWhatisAD620?AD620isalow-cost,high-precisioninstrumentationamplifier.Itonlyrequiresanexternalresistortosetthegain.Thegainrangeis1to10,000.CanIchangeAD620toAD623whenmakingMCUproducts?BothAD620andAD623aresingleinstrumentationamplifiers,andthepinarrangementisexactlythesame.Themaindifferenceis:AD620mustusepositiveandnegativepowersupplies,AD623canbeapositiveandnegativepowersupplyorasinglepowersupply.IftheoriginalboardisAD620,youcanreplaceitwith623;iftheoriginalboardisAD623,youmaynotbeabletoreplaceitwith620(itdependsonwhetherthepowersupplyoftheoriginalboardcircuitisdualpowersupplyorsinglepowersupply).AfterreplacingAD620andAD623insingle-chipproducts,theprogramcanworknormallywithoutmodification.WhatisthedifferencebetweenAD620BRandAD620AN?Theirpackagesaredifferent.WhatistheoutputresistanceofAD620?Howtoadjustit?AD620isakindoflowpowerconsumptioninstrumentamplifier,itsoutputresistanceisabout10K,thisistheinherentcharacteristicofthischip,generallyitisdifficulttoadjust.Ifyouhaverequirementsforoutputresistance,youcangenerallyuseanexternalcircuittosolveit.IsAD620apositivephaseamplificationorareversephaseamplification?AD620isaninstrumentamplifier,theoutputvoltageis[(Vin+)-(Vin-)]*gain.Ifthedesiredsignalis(Vin+)-(Vin-),thegainispositive,whichisequivalenttopositiveamplification.Conversely,ifthedesiredsignalis(Vin-)-(Vin+),thegainisequivalenttonegative,whichisequivalenttoreverseamplification.Whatisaninstrumentationamplifier?Instrumentationamplifier,animprovementofthedifferentialamplifier,hasaninputbuffer,doesnotrequireinputimpedancematching,sothattheamplifierissuitableformeasurementandelectronicinstruments

IRLU120PBF-VISHAY

IntroductionInrecentyears,withthecontinuousdevelopmentofnewtechnologies,storagebatteriesasapowersourcenotonlyplayanimportantroleintransportation(railroad,subway,ship),powergeneration,communications,aerospace,chemical,traditionalautomobilesandotherindustries.Inaddition,batterieshavealsobeguntobeusedinthefieldsofelectricvehicles(EV)andhybridelectricvehicles(HEV)aspowersourcesorpowerauxiliarypowersources.Doyouknowwhatare2featuresofbatteriescomparedwithdisposablerechargeablebatteries?Thatismultiplerecyclingandhighefficiencyandenergysaving.Whenthecarisnotstarted,itmustrelyonthebatterytosupplypowertothestarteruntilitdrivestheenginetorotate.Whenthebatteryvoltageisinsufficientorthebatteryisdamaged,itisdifficulttoprovidesufficientpower,thuscausingtheenginetofailtorun.Therefore,thisblogproposesthedesignofalow-batteryalarmsystemforcarbatteriesbasedonLM741.Ingeneral,whenthebatteryvoltagedropstoacertainlimit,itwillsendoutareminder.Theprincipleofthereminderisthatthecircuitjudgeswhetherthebatteryisworkingnormallybyinstallingasoundandlightsignalalarmsystem.Inthisway,wecanrechargeourcarorreplacethebatteryintime.CatalogIntroductionCatalogIDescriptionofLM741IIDesignoftheSystemIIICircuitDesign3.1SystemHardwareCircuitDesign3.2ReferencePowerSupplyCircuit3.3SamplingCircuit3.4OutputCircuit3.5AlarmPrinciple3.6WiringDiagramoftheSystemIVTestResultsoftheSystemFAQOrdering&QuantityIDescriptionofLM741TheLM741seriesaregeneral-purposeoperationalamplifiers.Itisintendedforawiderangeofanalogueapplications.Thehighgainandwiderangeofoperatingvoltageprovidesuperiorperformanceinintegrator,summingamplifier,andgeneralfeedbackapplications.LM741hasbothinvertinginputsandnon-invertinginputs.Whenthevoltageofthenon-invertinginput(+)ishigherthanthevoltageoftheinvertinginput(-),theoutputofthecomparatorishigh.Ifthevoltageattheinvertinginput(-)ishigherthanthenon-invertingterminal(+),theoutputislow.Theoutputoftheoperationalamplifieristheproductofgainandinputvoltage.IIDesignoftheSystemThelowbatteryalarmsystemismainlycomposedofreferencepowersupplycircuit,samplingcircuit,voltagecomparatorcircuitandoutputcircuit.Thereferencepowersupplycircuitconsistsofavoltageregulatorandacurrentlimitingresistor,whichisaddedtotheinvertinginputofthevoltagecomparatorandprovidesareferencevoltageforit.Thesamplingcircuitiscomposedoftworesistorsinseriestoformaseriesvoltagedivider,whichisusedastheinputsignalofthewholecircuit,andapartofthebatteryvoltageiscomparedwiththereferencevoltage.Thevoltagecomparatorcircuitjudgeswhethertheoutputishighlevelorlowlevelbycomparingthevoltageofthereferencepowersupplycircuitandthevoltageofthesamplingcircuit.Theoutputcircuitjudgeswhetherthelight-emittingdiodeisintheconductingstatebythereceivedoutputvoltagefromvoltagecomparator,therebygivinganalarmsignaltoindicatethebatterypoweristoolow.Figure1.StructureoftheSystemIIICircuitDesign3.1SystemHardwareCircuitDesignThehardwarecircuitoflowbatteryalarmsystemisshowninFigure2.ThesystemmainlyincludesvoltagecomparatorLM741,resistor,voltageregulatorandLED.Figure2.HardwareCircuit3.2ReferencePowerSupplyCircuitThereferencepowersupplycircuitconsistsofcurrentlimitingresistorR2andvoltageregulatorVDZ.ThissystemtakesthestablevoltageoftheregulatorasthereferencevoltageofthecomparatorLM741,andconnectsittotheinvertinginputoftheLM741.R2=100k.Thestablevoltageis5V.3.3SamplingCircuitR1andR3areconnectedinseriestoformasamplingcircuit,whichisconnectedtothein-phaseinputterminalofLM741.TheresistancevaluesofR1andR3areequal,taking100ktoformseriespartialvoltage.Theintermediatepointisthesamplingvoltage,thatis,takingpartofthebatteryvoltageasthedetectionvoltage,i.e.theinputvoltage.3.4OutputCircuitTheoutputcircuitconsistsofR4andLED.R4=1K,whichcanlimitthecurrent.AccordingtothevoltagevalueattheoutputofthevoltagecomparatortodeterminedwhethertheLEDisonoroff.3.5AlarmPrincipleWhenthebatteryvoltageishigherthan10V,thatis,thevoltageofsamplingcircuitexceeds5V,theinputsignalvoltageishigherthanthereferencevoltage,thenLM741outputshighlevel,andtheoutputvoltageisbatteryvoltage(10~12V).ItcanbeseenfromFigure4thatthepotentialofpin6ishigherthanthepotentialofpin7.LEDdonotemitlightbecauseofthereversevoltage.Thisindicatesthatthebatteryvoltageisnormalandthealarmfunctionisnotactivated.Whenthebatteryvoltageislowerthan10Vandtheinputsignalvoltage(5V)islowerthanthereferencevoltage,theLM741outputsalowlevel,thatis,theoutputvoltageiszero.Atthistime,thepotentialofpin7ishigherthanthepotentialofpin6,theLEDisturnedonduetotheforwardvoltage.Andthelightindicatesthatthebatterypoweristoolow.Thealarmfunctionisactivated.3.6WiringDiagramoftheSystemFigure3showsthewiringstructureoflowbatteryalarmsystem.Theautomobilebatteryisconnectedtothevoltagecomparisondevicethroughthecarkeyswitch,andprovidespowerfortheautomobilecircuitload(lightingsystem,instrumentsystem,etc.)Whenthebatteryvoltageisnormal,theloadvoltageisnormal.Andthevehiclecanstartnormally.Theinstrumentsystemcandisplayandworknormally.Whenthebatteryvoltageistoolow,thevoltagecomparisondevicewillsendoutalightalarmsignal.Atthesametime,ifthepowersupplyvoltagecannotreachtherequiredvoltagelevelofthesystem,thecorrespondinglighting,instrumentandothersystemswillnotoperate.Figure3.WiringDiagramoftheSystemIVTestResultsoftheSystemItcanbeseenfromtable1thatwhenthebatteryvoltageislowerthan10V,thealarmindicatorison;whenthebatteryvoltageishigherthan10V,thealarmindicatorisoff.Therefore,thecircuitcangiveanalarmwhenthebatteryvoltageislowerthan10V,andstopwhenthebatteryisrechargedtoabove10Vagain.Thealarmsystemdoesnotworkwhentheoutputvoltageofthebatteryisabove10V.Itfullyshowsthatthedesignschemeofthecircuitiscorrectandfeasible.TestResultsoftheSystemBatteryvoltage(V)BatteryvoltagestatusAlarmindicatorstatus6.8toolowon8.1lowon9.6lowon10.3(Aftercharging)normaloff12.8(Aftercharging)normaloff13.6(Aftercharging)toohightoffFAQWhatislm741opamp?AnLM741operationalamplifierisaDC-coupledhighgainelectronicvoltageamplifier.Ithasonlyoneop-ampinside.AnoperationalamplifierICisusedasacomparatorwhichcomparesthetwosignal,theinvertingandnon-invertingsignal.WhyOpampiscalled741?The741OpAmpICisamonolithicintegratedcircuit,comprisingofageneralpurposeOperationalAmplifier.ItwasfirstmanufacturedbyFairchildsemiconductorsintheyear1963.Thenumber741indicatesthatthisoperationalamplifierIChas7functionalpins,4pinscapableoftakinginputand1outputpin.Howdoesa741opampwork?ThemostcommonOp-Ampisthe741anditisusedinmanycircuits.TheOPAMPisaLinearAmplifierwithanamazingvarietyofuses.Itsmainpurposeistoamplify(increase)aweaksignal-alittlelikeaDarlingtonPair.TheOP-AMPhastwoinputs,INVERTING(-)andNON-INVERTING(+),andoneoutputatpin6.Howdoyoucalculatelm386gain?VoltageGainAnalysis:Withoutanyexternalcomponents,ithasagainofGv=2x15K/(150+1350)=20(26dB).Withacapacitor(orshortcutting)betweenpins1and8,ithasagainofGv=2x15K/150=200(46dB).WhydoestheIC741requiredualpowersupply?Operationalamplifiershavetwopowersupplyrailsbecausetheyusuallyneedtoswingbipolar-outputvoltagesthatgoeitherpositiveornegativeinresponsetothenormalrangeofinputsignals....Withoutthedualsuppliestheoutputsignalwouldclipatthegroundpotential.HowdoIcheckmy741IC?Testinga741ICThecircuitiscommonlycalledasvoltagefollower.Avoltageisappliedtopin3oftheop-ampthroughthevariableresistor(10K).AllweneedtodoistoverifywhetherthevoltagesV1andV2areexactlysameornot.Checkthemusingamulti-meter.WhatisIC741?Anopampisacomplexelectronicdevice,whichconsistsofresistors,capacitors,transistorsanddiodes.Itiscommerciallyavailableinintegratedcircuitform.MostcommonlyavailableandusedopampICisIC741.TheIC741isasmallchip.Itcompriseseightpins.Whatisgainbandwidthproductof741?Gain-BandwidthProduct:ForanOp-Ampthegain,Gisdefinedasthegainwhenasignalisfeddifferentiallyintotheop-ampandnofeedbackloopispresent....ItisgenerallygiveninV/s,andforthe741op-ampissomethingcloseto1v/s.WhatarethefeaturesofIC741?Shortcircuitandoverloadprotectionprovided.Intheory,thedcoutputvoltagewillbezeroifboththeinputsofthe741ICareconnectedtotheground.Lowpowerconsumption.Largecommonmoderejectionratio(CMRR)anddifferentialvoltageranges.Noexternalfrequencycompensationisrequired.Whichop-amp(LM356orLM741)isthebetterchoiceforhigherfrequencyapplications?Um,theLM356isanaudiopoweramplifierwitha300KHzbandwidth.TheLM741isanoperationalamplifierwithatypicalunitygainbandwidthof1MHz.Inotherwords,theyareentirelydifferentsortsofthingsandnotatallinterchangeable.Neitherisverygoodathigherfrequencies.YoumightbethinkingoftheLF356,whichisaJFETinputoperationalamplifierwithaunitygainbandwidtharound5MHz.MuchbetterpartinalmosteverydimensionthantheLM741.CanweuseanLM324insteadofanLM741forconstructinganop-ampintegrator?Yes.Itwilllikelyperformslightlybettertooasithasaslightlybetterspecification(frequency,slewrate,etc),plusyougetfouridenticalopampsinasingle14pinpackage.IntroductionTheLM386isapoweramplifierdesignedforuseinlowvoltageconsumerapplications.Thegainisinternallysetto20tokeepexternalpartcountlow,buttheadditionofanexternalresistorandcapacitorbetweenpins1and8willincreasethegaintoanyvaluefrom20to200.Theinputsaregroundreferencedwhiletheoutputautomaticallybiasestoone-halfthesupplyvoltage.Thequiescentpowerdrainisonly24mWwhenoperatingfroma6Vsupply,makingtheLM386idealforbatteryoperation.CatalogIntroductionCatalogIHowdoesLM386InternalCircuitWork?1.1Inputstage1.2VoltageAmplifierstage1.3Outputstage1.4FeedbackNetworkIILM386ApplicationCircuit2.1CircuitofInfraredalarm2.2CircuitofAutomobileVoiceHorn2.3CircuitofMicrocomputerStereoPowerAmplifierFAQOrdering&QuantityIHowdoesLM386InternalCircuitWork?TheprincipleofLM386internalcircuitisshowninthefigure.Theinternalcircuitisbasedonatypicalaudiopoweramplifierconfiguration,oftenreferredtoasLintopology.LM386internalcircuitisdividedintoinputstage,voltageamplifierstage(VAS),outputstage(OPS)andfeedbacknetwork.Figure1.LM386InternalCircuit1.1InputstageThefirstmoduleisthePNPemitterfolloweramplifier(Q1,Q3).ItsetstheinputimpedanceanddefinestheDCoperatingpointtoraisetheinputvoltagefromtheground,sothecircuitwillacceptthenegativeinputsignalto-0.4V.Both50Kinputresistors(R1,R3)haveestablishedpathstothebasecurrentground,andtheinputsneedtobecoupledtoavoidinterferingwiththeinternalbias.Sotheinputimpedanceisdeterminedbytheseresistorsandissetto50K.Analysisofvoltagegain:Thegainoflongtailpair(Q2,Q4)ofdifferentialamplifierisregulatedbytwogainsettingresistors1.35k+150(R5+R5).Externalpins1and8canadjustthegainfrom20(minimum)to200(maximum).Thevoltagegaincanbecalculatedunderstaticconditions(withoutinputsignalapplied)asfollows:Figure2.AnalysisofLM386voltagegainThevoltage(vdiff)atbothendsofR4andR5isonlythedifferentialinputvoltage(VIN),becausethebaseemittervoltagedropofPNPtransistors(Q1,Q2,Q3andQ4)onbothsidesofLTPisthesame.ThecurrentmirrorformedbyQ5andQ6producesequalcurrentonbothsidesoftheLTP.ThecurrentismarkedasI.Duetothecurrentmirror,thecurrentintensitythroughR8isequalto2I,whileignoringthecurrent(i7)throughthetwo15Kresistors(R6,R7).thesetworesistorshavealargerimpedancecomparedtotherestofthecircuit,thereby:Inthefigureabove,itiseasytoseethatifi7=0,then:Theformulacanalsoberewritteninamoregeneralway:Z1-5andZ1-8aretheimpedancebetweenthecorrespondingpins.Withoutanyexternalcomponents,thegainisGV=2x15k/(150+1350)=20(26dB).Useacapacitor(orshortcut)betweenpin1and8,thenitsgainofGV=2x15k/150=200(46db).1.2VoltageAmplifierstageThecommonemitteramplifier(Q7)amplifiesthelowamplitudeinputsignaltotheappropriateleveldirectlycoupledtotheoutputstage.1.3OutputstageItisclassABpoweramplifier,thatis,push-pullconfiguration.Eachtransistoramplifiesitscorrespondinghalfwave.BecausethegaindifferencebetweenQ9andQ10ofPNPtransistorsisinacompoundPNPtransistorconfiguration,TOTAL=Q9XQ10.Dividercompensation:DiodesD1andD2areusedtocompensateforcrossdistortion.Infact,inapush-pulltopology,thetransistordoesnotstartconductinguntiltheinputsignalbeginstoexceeditsforwardvoltage(Vbe).Theforwardvoltage(VBE)isthevoltageatthebaseemitterjunction(usuallyabout0.6V).Inordertooffsettheminimumconductionlimit(Vbe)ofthetransistors,theyneedtobebiasedsothattheiridlingvoltagewillneverbelowerthantheforwardvoltage(Vbe).Acertainamountofcurrent(calledabiascurrent)willcontinuouslyfeedintothebaseofthetransistortoensurethattheymaintainthesacrificialefficiencyofconduction.Itisprovedthatusingdiodesisoneofthebestsolutions.Itprovidesatemperature-dependentpressuredrop.Andbymatchingthethermalcoefficienttothetransistor,thebiascurrentcanbekeptfairlystable.Ifaccurateheattracingisrequired,installthediodesonthesameheatsinkasthepowertransistor.Sinceonediodeisusuallynotenough,amplifiersusuallyusemultiplediodejunctions1.4FeedbackNetworkAnegativefeedbackisappliedfromtheoutputtotheemitterQ4viatheresistorR8.ThefunctionoftheDCfeedbackistostabilizetheoutputDCbiasvoltagetohalfofthesupplyvoltage.ThefunctionsofDCfeedbackareasfollows:IfforsomereasonVOincreases,thecorrespondingcurrentincrementwillflowthroughR8andintotheemitterofQ4.Therefore,theincreaseofcollectorcurrentofQ4leadstothepositiveincreaseofbasevoltageofQ7.ThisleadstoanincreaseinthecollectorcurrentofQ7,whichreducesthebasevoltageofQ7,thusreducingVo.IILM386ApplicationCircuit2.1CircuitofInfraredalarmFigure3.CircuitofInfraredalarmFigure3showsthecircuitofinfraredalarm.ThecircuitiscomposedofanANDgatecircuit,amonostabledelaycircuit,afour-wayinfraredtransmittingandreceivingcircuit,atriggerandatwo-colorlight-emittingcircuit,andanaudioalarmcircuit.FourpairsofwarninglinesfortransmissionandreceptioniscomposedofHF1~HF4(infraredlight-emittingdiodes)andBG1~BG4(infraredreceivingpairingtubes).Ifsomeonecrossesthewarninglineandtheinfraredbeamisblocked,thecorrespondingmatchingtubewillbecutoff.AndtheinputofthecorrespondingNANDgateishighlevel.Itmakesthetriggerterminalpin2ofIC3(555)obtainanegativedifferentialpulse,thatis,theoutputterminaloftheANDgatecomposedofD1~D4.Therefore,the555isset,andthehighlevelisoutputfrompin3whichmakesBG5saturatedandturnedon.ThechipIC4(KD-9562)ispoweredonandanalarmsoundisgiven.ThedelaywidthofIC3monostablecircuittd=1.1Rw1R3determinesthesoundtime.Thedelayalarmtimecorrespondingtotheparametersinthefigureisabout100seconds.Atthesametime,thecorrespondingtimecanbechangedbychangingthevalueofWandCaccordingtothespecificsituation.ThevoltagestabilizingtubeDWadopts2cw7or2cw10,andthevoltagerangeisabout3VtoprotectthemusicintegrationKD-9562,soastopreventitfromburningduetoover-voltage(highvoltage).ThechipKD-9562isaneightanalogsoundintegratedcircuit,whichcanselectthecorrespondingmusicaccordingtotheusesituationandpurpose.LM386isasinglepoweraudiopoweramplifierintegratedcircuit,whichisusedtoexpandtherangeofalarmsound.F1-1~F1-6,F2-1~F2-6usesixinverterCD4069.Two-colorlight-emittingdiodesLED1~LED4adopt2EF303.Undernormalconditions,theyemitgreenlight,andwhensomeonecrossesthewarningline,theysendoutredwarninglight.2.2CircuitofAutomobileVoiceHornFigure4.CircuitofAutomobileVoiceHornTheleftsideofthedottedlineinFigure4istheoriginalcircuitdiagramofthevehicleelectrichorn.SListheelectrichornbuttonswitchonthesteeringwheel.S2isanewlyaddedSPDTSwitch,whichisusedforswitchingbetweenelectrichornandvoicehornoftheoriginalvehicle.WhentheswitchS2issetto2,presstheswitchSl,thecapacitorClischarged,thetransistorsVTl,VT2turnon,therelayJlpullsin.J1-1isclosedandheldfor15secondstosupplypowertothecircuit.IClisadedicatedvoiceintegratedcircuitHL-169A.Sinceitsworkingtimeis2.8seconds,theself-excitedmultivibratoriscomposedoftransistorsVT3andVT4.Every3seconds,ahighlevelisoutputasatriggersignal,sothatICloutputsavoicesignalevery3seconds,andsendsittoIC2foraudiopoweramplification,andthespeakerBLemitsvoice.2.3CircuitofMicrocomputerStereoPowerAmplifierBecausetheaudiosignalamplitudeofthelineoutputofthesoundcardistoolarge,theLM386canbedriventopushthespeaker.Inaddition,duetotheinterferenceofvideosignalwhenplayingVCD,itisnotgoodtoconnecttheVCDaccordingtothetypicalcircuit,soitisnecessarytoaddsomecomponentsanddebugthecomponentvalues.TheschematicdiagramisshowninFigure5.Figure5.CircuitofMicrocomputerStereoPowerAmplifierLM386hastwoinputterminals,3pinin-phaseinputand2pininvertinginput.Theinputsignalcanbeinputfromanyendandtheotherinputterminalcanbegrounded.TheinputendisconnectedwithcapacitorC4inordertofilteroutthevideointerferencewhenplayingVCD.Thevaluecanbeincreasedappropriately,butitcanbeusedwithorwithoutC4whenplayingCD.Thepin1andpin8aregaincontrolterminals,whicharecomposedofC2andW2.Thesmallertheresistance,thehigherthegain.ItismoreappropriatetoadjustthegainofW2toabout150.Ifthegainistoohigh,itwilleasilycauseself-excitation.Pin7isconnectedtoa10capacitor.ThehighfrequencycomponentattenuationcircuitiscomposedofR2andC6toeliminatethecrashsoundfromtheloudspeaker.ThecapacityofC6canbeadjustedaccordingtotheactualeffect.Pin6isconnectedtothegroundwitha0.1capacitor,whichactsasafiltertoeliminatethestatichumoftheamplifier.Pin5isconnectedtothecouplingcapacitorC3.Ifonlyoneconespeakerisconnectedtoonechannel,C3capacityshouldnotexceed470,otherwisetheloudspeakerwillbeblockedwhenplayinglowmusic.Ifhigh-frequencyandlow-frequencycrossovertechnologyisadopted,thecapacityofC3canbeincreasedtomakethebassfullyreflected.W1isusedtoadjusttheoutputvolume,whichisparticularlyconvenientwhenplayinggamesorlisteningtoCDs.FAQHowdoesanLM386work?TheLm386integratedchipisalowpoweraudiofrequencyamplifier,whichuseslowlevelpowersupplylikebatteriesinelectroniccircuits.Itisdesignedas8pinminiDIPpackage.Thisprovidesvoltageamplificationof20.Byusingexternalpartsvoltagegaincanberaisedupto200.Islm386anopamp?TheLM386isatypeofoperationalamplifier(Op-Amp)....Inanamplifiercircuit,theLM386takesanaudioinputsignalandincreasesitspotentialanywherefrom20to200times.Thatamplificationiswhatsknownasthevoltagegain.Whatislm386IC?TheLM386isanintegratedcircuitcontainingalowvoltageaudiopoweramplifier.Itissuitableforbattery-powereddevicessuchasradios,guitaramplifiers,andhobbyelectronicsprojects.Howdoyoucalculatelm386gain?VoltageGainAnalysis:Withoutanyexternalcomponents,ithasagainofGv=2x15K/(150+1350)=20(26dB).Withacapacitor(orshortcutting)betweenpins1and8,ithasagainofGv=2x15K/150=200(46dB).WhichICisusedinaudioamplifier?TheICLM386isalow-poweraudioamplifier,anditutilizeslowpowersupplylikebatteriesinelectricalandelectroniccircuits.ThisICisavailableinthepackageofmini8-pinDIP.WhataresomeprojectsthatusetheLM386audioamplifiercircuit?LM386isanintegratedclassABampandisgoodforbeginnerssmallaudioamplifierapplicationsforexampleinaRFreceiver,smallStereosystem,cheaplowvoltageamplifieretcdrawbacksisthatitcannothandlemuchpowerandhencecreatesdistortionwhenyoucrankupthevolumetoomuch..SootherICsareusedinpractical.HowtomakeanLM386audioamplifiercircuit?

IRLU120PBF-VISHAY

IntroductonLM386isalowvoltageaudiopoweramplifier.LM386adopts8-pindoublein-lineplasticpackagewithworkingvoltageof4V-15V.Whenthepowersupplyvoltageis12V,300mWoutputpowercanbeobtainedonan8load.VariousoscillatorscanbeeasilyproducedwithLM386.CatalogIntroductonCatalogISimplestOscillatorIIBlockingOscillatorIIIElectronicPianoIVSquare-waveOscillatorVSinusoidalOscillatorFAQOrdering&QuantityISimplestOscillatorFigure1.CircuitofSimplestOscillatorInFigure1,theoutputendandin-phaseinputendofLM386areconnectedbypiezoelectricceramicchipHTD.Theamplifierformspositivefeedbackandgeneratesoscillation.HereHTDisbothafeedbackcapacitorandasound-generatingdevice.Componentparametersinthefigure:D1~D4are1N4001,C1=220pF,HTDispiezoelectricceramicsheetwithauxiliaryacousticcavity.IIBlockingOscillatorFigure2.CircuitofBlockingOscillatorAsshowninFigure2,asimpleoscillatorconsisitofLM386,C3,C4andloudspeakers.RPandC2makethisoscillatorproduceblocking-oscillation.Afterconnectingthepowersupply,LM386doesnotworkbecausetheinitialterminalvoltageofC2iszero,andthepowersupplychargesC2throughRP.WhenC2chargingvoltageishigherthanacertainvalue,LM386oscillatorstartstovibrate.Astheamplitudecontinuestoincrease,thecurrentconsumptionoftheoscillatoralsoincreases.ThiscurrentflowsthroughRP,anditsvoltagedroponRPalsoincreases,causingtheLM386powersupplyterminal6pinvoltagetocontinuetodrop.EventuallytheLM386cannotworkandtheoscillatorstops.ThepowersupplyrechargesC2viaRPagain,causingthevoltageatC2torise.WhenthevoltageatC2risestoacertainvalue,theLM386oscillatorstartsagain.Inthisway,theoscillatorwillproduceblocking-oscillation,andthespeakeremitsbeep,beep,beepsound.Componentparametersinthefigure:D1~D4are1N4001,C1=C3=220F,thermal overload symbolC2=47F.C4=0.01F ,types of diodesRP=4.7K.IIIElectronicPianoFigure3.CircuitofElectronicPianoFigure3isasimpleelectronicpianocircuit.Onthepin3ofLM386,theintegratedcircuithasa10Kresistortoground.Thisbuilt-inresistorandtenscaleresistorsRP1~RP10constitutethetimingresistoroftheoscillator.C2isthetimingcapacitor.ByadjustingthevaluesofRP1~RP10,thespeakerscansequentiallyemitmusicalsoundsfromlowoctavedo,re,mitohighoctavedo,re,mi.KI~K10arekeyswitches.Componentparametersinthefigure:Cl=C3=220F.C2=2200FIVSquare-waveOscillatorFigure4.CircuitofSquare-waveOscillatorFigure4showsasquare-waveoscillatorcomposedofLM386.R1isthetimingresistor.C2isthetimingcapacitor.R2andR3providevoltagebiasforLM386in-phaseinput.BecausethevoltageattheC2terminalcannotchangeabruptly,theinvertinginputterminalpin2oftheLM386islowlevel,andpin5isthemidpointoftheinternalOTLoutputstageoftheamplifier.Itis1/2Vocinstaticstate,anditissuppliedtothethird-phaseinputpin3afterdividingpressureviaR2andR3.Obviouslythepotentialofthispinishigherthanthesecondpin.Therefore,pin5outputshighlevel.ThishighlevelchargesC2viaR1.WhenthevoltageofC2terminalishigherthanthepotentialofpin3,pin5outputslowlevel.C2dischargestopin5viaR1.WhenC2isdischarged,thepotentialofpin2dropsandislowerthanthepotentialofpin3.Pin5outputshighlevelagain.Inthisway,thecircuitformsoscillation,andtheoscillationsignaldrivestheloudspeakertosoundthroughC3.Componentparametersinthefigure:C1=C3=220F,smd resistors codesC2=0.33F.R1=22K,switch diodesR2=1K.R3=9.4KVSinusoidalOscillatorFigure5.CircuitofSinusoidalOscillatorFigure5isasinusoidaloscillatormadeofLM386.ThecircuitadoptsWienbridgeoscillationmode,andtheoutputsignaldistortioncoefficientofthecircuitisverylow.TheflashlampHandtheresistorR3formanegativefeedbackcircuit,whichkeepstheamplitudeoftheoscillatoroutputsignalstableandhaslowdistortion.WhenthevaluesofcapacitorsC1andC2arethesame,theoscillationfrequencyofthecircuitcanbeobtainedbytheformulaf=1/2C1R1R2.Inactualproduction,Hcanuse3V,15mAflashlamp.FAQHowdoesanLM386work?TheLm386integratedchipisalowpoweraudiofrequencyamplifier,whichuseslowlevelpowersupplylikebatteriesinelectroniccircuits.Itisdesignedas8pinminiDIPpackage.Thisprovidesvoltageamplificationof20.Byusingexternalpartsvoltagegaincanberaisedupto200.Islm386anopamp?TheLM386isatypeofoperationalamplifier(Op-Amp)....Inanamplifiercircuit,theLM386takesanaudioinputsignalandincreasesitspotentialanywherefrom20to200times.Thatamplificationiswhatsknownasthevoltagegain.Whatislm386IC?TheLM386isanintegratedcircuitcontainingalowvoltageaudiopoweramplifier.Itissuitableforbattery-powereddevicessuchasradios,guitaramplifiers,andhobbyelectronicsprojects.Howdoyoucalculatelm386gain?VoltageGainAnalysis:Withoutanyexternalcomponents,ithasagainofGv=2x15K/(150+1350)=20(26dB).Withacapacitor(orshortcutting)betweenpins1and8,ithasagainofGv=2x15K/150=200(46dB).WhichICisusedinaudioamplifier?TheICLM386isalow-poweraudioamplifier,anditutilizeslowpowersupplylikebatteriesinelectricalandelectroniccircuits.ThisICisavailableinthepackageofmini8-pinDIP.WhataresomeprojectsthatusetheLM386audioamplifiercircuit?LM386isanintegratedclassABampandisgoodforbeginnerssmallaudioamplifierapplicationsforexampleinaRFreceiver,smallStereosystem,cheaplowvoltageamplifieretcdrawbacksisthatitcannothandlemuchpowerandhencecreatesdistortionwhenyoucrankupthevolumetoomuch..SootherICsareusedinpractical.HowtomakeanLM386audioamplifiercircuit?

IDescriptionThisblogusesLM386integratedblockasthecoredevicetomakeasimplesoundamplifier.Itsproductioncostisrelativelylow.Thisblogissuitableforbeginnerstolearnaboutpowertubes,integratedoperationalamplifiers,speakers,languagechipsandothercomponents.Sowecanmastertheprinciples,characteristicsandusageofthebasicamplifiercircuitandpoweramplifiercircuit.Figure1.LM386CatalogIDescriptionIIIntroductiontoLM3862.1Features2.2InternalStructureIIIWorkingPrincipleofLM386SoundAmplifierIVLM386SoundAmplifierDebuggingVConclusionFAQOrdering&QuantityIIIntroductiontoLM3862.1FeaturesLM386isakindofaudiointegratedamplifier.Ithastheadvantagesoflowpowerconsumption,adjustableinternalchaingainadjustment,largepowersupplyvoltagerange,fewexternalcomponentsandlowtotalharmonicdistortion.Therefore,LM386iswidelyusedinrecordersandradios,mainlyinlow-voltageconsumerproducts.LM386featuresare:BatteryOperationMinimumExternalPartsWideSupplyVoltageRange:4V12Vor5V18VLowQuiescentCurrentDrain:4mAVoltageGainsfrom20to200Ground-ReferencedInputSelf-CenteringOutputQuiescentVoltageLowDistortion:0.2%(AV=20,VS=6V,RL=8,PO=125mW,f=1kHz)Availablein8-PinMSOPPackageBasedonthecharacteristicsshownabove,lm386componentsarewidelyusedincommunicationequipment,smallradios,andwalkie-talkiecircuits.Itisalsocalleduniversalpoweramplifiercircuitbythemajorityofelectronicenthusiasts.2.2InternalStructureLM386adopts8-pindualin-linepackage.SeeFigure2forthepinarrangementdiagram.Figure2.LM386PinArrangementPin6isconnectedtothepositivepoleofthepowersupply;Pin4aregrounded;Pin2invertinginputterminal;Pin3non-invertinginputterminal;Pin5istheoutputterminal;Pins1,7,and8areusedtoimprovetheperformanceofthecircuit.Theexternalcomponentends,andtheinternalcircuitisathree-stageamplifiercircuit:The1ststageconsistsofVT1~VT6toformadifferentialamplifiercircuit,The2ndstageiscomposedofVT7voltageamplifiercircuit,The3rdstageiscomposedofVT8~VT10toformacomplementarysymmetricalOTLoutputcircuitthatcaneliminatecrossoverdistortion.R5,R6,andR7formanegativefeedbacknetwork.IIIWorkingPrincipleofLM386SoundAmplifierThecoreoftheLM386soundamplifieristheLM386poweramplifierintegratedcircuit.AsshowninFigure3.TheelectretmicrophoneB1convertssoundsignalsintoelectricalsignals.Thissignalisveryweak,howtoamplifyit?WecanaddthecouplingcapacitorC1tothebaseofVT1,andVT1formsacommonemitteramplifiercircuittoamplifythesignal.Also,thesignalisoutputfromthecollectorofVT1,andaddedtotheinvertinginputterminalofLM386viacouplingcapacitorC2topin2andpin3isgrounded.AfterthesignalisamplifiedbytheinternalthreestagesofLM386,thesignalisoutputfrompin5,andthenpassesthroughthecouplingcapacitor.C3issenttothespeakers.Aftergoingthroughtheseprocesses,itcanmakeasound.Figure3.LM386SoundAmplifierFigure4.LM386AudioAmplifierCircuitThenhowtoadjustthesignalmagnificationofLM386?Here,wecanconnectanadjustableresistorR5andcapacitorC6topin1andpin8toformaseriesRCnetwork.WhenR5=0,thevoltagemagnificationis200.Pin7isconnectedtocapacitorC5topreventLM386fromgeneratingself-excitation.Inaddition,pin5isgroundedthroughR4andC4tomakethespeakersoundsofter.IVLM386SoundAmplifierDebuggingAfterthecircuitisassembled,weshouldcarefullycheckforerrorsorfalsesoldering.Ifthereisnoabnormalityaftertheinspection,turnonthe6Vpowersupplyfordebugging:Step1:Dontpickupthemicrophonefirst.Whenthereisnoinputsignal,testthequiescentcurrentofthewholemachine,whichisabout7mA.Step2:TestthestaticvoltagevalueofeachpinofLM386,asshowninFigure2.Step3:Afterthevoltageandcurrentarenormal,placetheRPvolumeregulatorinthemiddleandtouchthebaseofVT1withascrewdriver.Thespeakerwillemitaclickclicksound,indicatingthatthecircuitisnormal.Step4:ConnectthemicrophoneB1,andthenfine-tunetheRP.Ifnothinggoeswrong,speakintothemicrophone,thespeakershouldhaveamplifiedsound.Ifthereisnosound,checkwhetherthemicrophonecableisconnectedincorrectlyorthequalityofthemicrophoneisdefective.Step5:Whenusingasoundamplifier,donotplacethemicrophoneandspeakertooclosetogether.Iftheyareunfortunatelytooclose,thespeakerswillmakeaharshsound.Therefore,itisbesttouseshieldedwireforthemicrophonelead-out.Figure5.LM386VConclusionThroughthedesignofthisblog,wehaveanessentialunderstandingoftheworkingprincipleofLM386.Wehavemasteredthepinfunction,internalstructurecircuitandworkingprincipleofLM386.Inaddition,thesoundamplifiermadebyLM386hasthecharacteristicsofsimplecircuit,convenientdebugging,andcompletefunctions.Afterreadingthisblog,haveyoubetterunderstandLM386?FAQHowdoesanLM386work?TheLm386integratedchipisalowpoweraudiofrequencyamplifier,whichuseslowlevelpowersupplylikebatteriesinelectroniccircuits.Itisdesignedas8pinminiDIPpackage.Thisprovidesvoltageamplificationof20.Byusingexternalpartsvoltagegaincanberaisedupto200.Islm386anopamp?TheLM386isatypeofoperationalamplifier(Op-Amp)....Inanamplifiercircuit,theLM386takesanaudioinputsignalandincreasesitspotentialanywherefrom20to200times.Thatamplificationiswhatsknownasthevoltagegain.Whatislm386IC?TheLM386isanintegratedcircuitcontainingalowvoltageaudiopoweramplifier.Itissuitableforbattery-powereddevicessuchasradios,guitaramplifiers,andhobbyelectronicsprojects.Howdoyoucalculatelm386gain?VoltageGainAnalysis:Withoutanyexternalcomponents,ithasagainofGv=2x15K/(150+1350)=20(26dB).Withacapacitor(orshortcutting)betweenpins1and8,ithasagainofGv=2x15K/150=200(46dB).WhichICisusedinaudioamplifier?TheICLM386isalow-poweraudioamplifier,anditutilizeslowpowersupplylikebatteriesinelectricalandelectroniccircuits.ThisICisavailableinthepackageofmini8-pinDIP.WhataresomeprojectsthatusetheLM386audioamplifiercircuit?LM386isanintegratedclassABampandisgoodforbeginnerssmallaudioamplifierapplicationsforexampleinaRFreceiver,smallStereosystem,cheaplowvoltageamplifieretcdrawbacksisthatitcannothandlemuchpowerandhencecreatesdistortionwhenyoucrankupthevolumetoomuch..SootherICsareusedinpractical.HowtomakeanLM386audioamplifiercircuit?IDescriptionThisblogintroducesandanalyzes4simpleandeasy74LS00NandGatecircuitdiagrams.Itsincluding:SquareWaveGeneratorCircuit,PulseGeneratorCircuit,LEDLightCircuit.Andintheend,wewillanalyzethecircuitthatturnsthetimerintoacountdowntimerindetail.ThisVideoisAnIntroductionof7400LogicDevicesCatalogIDescriptionIISquareWaveGeneratorCircuitIIIPulseGeneratorCircuitIVLEDLightCircuitVTurnTimerintoCountdownTimer5.1SchemeDesign5.2ImplementationofSchemeDesignOrdering&QuantityIISquareWaveGeneratorCircuitLetstakealookatthefigurebelow.Itsasquarewavegeneratorcircuit.Thiscircuitcontainsa74LS00NandGateintegratedcircuit.Figure1.SquareWaveGeneratorCircuitDiagramAmongthiscircuitdiagram:NANDgates1,2andexternalRCtimeconstantcomponentsformanoscillatorcircuitNANDgate3isabufferoutputstage.AslongasthecapacityofCischanged,squarewaveoutputsofdifferentfrequenciescanbeobtained.IIIPulseGeneratorCircuitFigure2.PulseSignalGeneratorCircuitDiagramThecircuitdiagramisshowninFigure2anditsasimplepulsesignalgeneratorcircuit.ThesignalgeneratormainlyusestwoTTLintegratedcircuits(74LS00and74LS221).Sowhychoosethesetwocircuits?Thatisbecause,thesetwocircuitscanbeusedtogenerateapulsesignalof=4s.Besides,itusesfewercomponentsandisconvenientfordebuggingandmaintenance.IVLEDLightCircuitThiscircuitismadewithNE555,74LS00,74LS154,74LS193andLEDlights,andtheproductionprocessisverysimple.Whenweturnonthepower,hereishowitworksis:WhentheoutputQ0ofthe74LS154decoderislow,the74LS193isapositivecounter.Atthistime,theLEDsareindividuallylitfromD1...D16;WhentheoutputQ15ofthe74LS154decoderislow,the74LS193isacountdowncounter.Atthistime,theLEDsareindividuallylitfromD16...D1.Figure3.LEDLightCircuitDiagramFromtheabovewecanseethat:theLEDlightsturnonfromD1toD16,andthenbacktoD1fromD16,andsoon.VTurnTimerintoCountdownTimerGenerally,therearetwodesignideasforturningatimerintoacountdowntimer:First,changethecountingchipinthetimer;Second,resetthefunctionofthechip.Besides,thereisactuallyanotherwaytoachievethisgoal:Byappliyingthe74LS00and74LS20chipstoreversetheresultsonthedisplay,soastoachievethepurposeofcountingdown.5.1SchemeDesignTheresultdisplayedbyeachdigitofthetimerisanincrementalvalue,suchas0.1.2.3.4.5.6.7.8.9.Yet,thecountdowntimerdisplaysadecreasingvalue,suchas9.8.7.6.5.4.3.2.1.0.Aslongasthedisplayresultconversioniscompletedwithasuitablelogiccircuit,thetimercanbeturnedintoacountdowntimer.Atfirst,weneedtofindthelogicalrelationshipbetweenthetimerdisplayresultandthecountdowntimerdisplayresult.Table1belowliststheBCDcodescorrespondingtoeachdisplayresultofthetimerandcountdowntimer.Fromthistable,youcaneasilyfindtheBCDcodesofthetimerandcountdowntimer:ThelowestbitQ1andY1areopposite;WhileQ2andY2arethesame;RelationshipbetweenQ3andY3:Y3ofthecountdowntimeristheexclusiveORoftimerQ3andQ2;RelationshipbetweenQ4andY4:TheY4bitofthecountdowntimeristheoppositevalueoftheORofQ4,Q3,andQ2ofthetimer,whichisalsoequaltothenon-re-ANDofQ4,Q3,andQ2.Table1.CorrespondingBCDCodeDisplayedby(Down)TimerTheabovelogicalexpressionis:Therefore,aslongasyouchooseacircuitthatcancompletetheabovelogicconversionrelationship,youcanrealizethedesignfromatimertoacountdowntimer.Thefigure?showsatwo-digittimercircuit.Afteraddingtheaboveconversioncircuit,itbecomesthefigure3showsthecountdowncircuit.Figure4.TimerCircuitDisplaying2DigitsFigure5.CountdownCircuitDiagram5.2ImplementationofSchemeDesignTwokindsofchips74LS00and74LS20areuesdhere.Theformerarefourtwo-inputNANDgates,whichareusedtocompletetheconversionofY1andgeneratethenegationofQ4,Q3,andQ2.Thelatteraretwofour-inputNANDgates,whichareusedtoobtainY4fromthenon-reANDofQ4,Q3,andQ2.Insummary,wecanfollowthelogicalrelationshipasfollows:ThelogicdiagramisshowninFigure6.Figure6.LogicDiagramKnowingthattheXORgateoperationcanbecompleted,theY3conversioncanbecompleted.Theconnectioncircuitdiagramoftheabove-mentionedY4,Y3,Y1conversionspecificphysicalobjectsisshowninFigure7.Figure7.Y4,Y3,Y1ConversionSpecificPhysicalConnectionDiagramFigure8showstheactualpictureofthecountdowntimer.Figure8.CountdownTimerSofar,thetimerhasbecomeacountdowntimer.Throughthisdesignmethod,thereisnoneedtochangetheoriginalcountercircuit,isitparticularlytrouble-free?

I.IntroductionTDA7294isaveryinnovativeDMOShigh-powerintegratedamplifiercircuitlaunchedbythefamousEuropeanSGS-THOMSONSTMicroelectronicstomainlandChinainthe1990s.Itsweepsawaytheraw,cold,andhardtonesofthepreviouslinearintegratedpoweramplifiersandthickfilmintegration,andiswidelyusedintheHI-FIfield:suchashometheater,activespeakers,etc.Thedesignofthischipfocusesontone,andhastheadvantagesofbipolarsignalprocessingcircuitandpowerMOS.Ithasthecharacteristicsofhighvoltageresistance,lownoise,lowdistortion,andveryaffinityforreplayingsound;andhasasilentstandbyfunction,short-circuitcurrentandoverheatprotectionfunctionstomakeitsperformancemoreperfect.ThisarticlewillintroduceseveralpoweramplifiercircuitdesignsbasedonTDA7294.CatalogI.IntroductionII.OCLCircuitIII.BTLCircuitIV.ConstantCurrentPowerAmplifierV.Hi-FiIntegratedPowerAmplifierVI.ActiveSubwooferAmplifierAddsStandbyFunctionVII.HighFidelityPowerAmplifierVIII.ClassABPowerAmplifierIX.Two-channelPowerAmplifierX.100WPowerAmplifierCircuitOrdering&QuantityII.OCLCircuitTheOCLcircuitdiagramisshowninFigure1.Thiscircuitisadual-channel70WpoweramplifiercomposedoftwoTDA7294.Therearefewexternalcomponentsandsimplecircuit.Whenthepowersupplyvoltageis35V,70Wcontinuousoutputpowercanbeobtainedonan8ohmload.Itisverysuitableforplaybackinanenvironmentbelow30squaremeters.Ifthespeakerimpedanceislessthan8ohms,thepowersupplyvoltageshouldbereducedaccordingly.Figure1OCLCircuitDiagramIII.BTLCircuitTheBTLcircuitisshowninFigure2.ItusestwoTDA7294bridgestoformaBTLpoweramplifiercircuit.Theoutputpowercanreachmorethan150W.Itissuitableforplacesthatrequirehighpowersuchasdancehalls.4TDA7294arerequiredforstereo.Whenthepowersupplyvoltageis25V,acontinuousoutputpowerof150Wcanbeobtainedonan8ohmload.Whenthepowersupplyis35V,acontinuousoutputpowerof180Wcanbeobtainedona16ohmload.WhenuseTDA7294asBTLpoweramplifier,theloadmustnotbelessthan8ohms.Figure2BTLCircuitDiagramIV.ConstantCurrentPowerAmplifierThispoweramplifiercircuitissomewhatdifferentfromtheprevioustwostructures.Itsfeedbackcircuitiscurrentsampling,voltagesummationandnegativefeedback.Thiskindofcircuitstructureistheconstantcurrentpoweramplifierthatpeopleoftensay.Thespecificanalysisofthecircuitwillnotbedetailed,onlythemoreprominentadvantagescomparedwiththetraditionalconstantvoltagepoweramplifierwillbeintroduced.(1)Theoutputcurrentofthepoweramplifierhasnothingtodowiththeloadimpedance.Eveniftheloadisshort-circuited,itwillnotcausetheamplifiertooverheat.(2)Theoutputpowerincreaseswiththeincreaseofloadimpedance.Pushingthespeakerloadwithinacertainpowerreservecanensurethebassstrengthandhighfrequencyresolutionoftheoriginalmusicsignal.(3)Theforceactingonthevoicecoilofthespeakeronlydependsonthecurrent.Theuseoffluid-controlledoscillationtopromotethespeakermustbefasterthanthevoltage-controlledoscillation,sothattheinputandoutputimpedanceofthespeakervibrationsystemcanbeeasilymatched.Theconstantcurrentpoweramplifiercircuitisactuallyacontrolledcurrentsourcecontrolledbytheinputsignalvoltage.Itsinternalfeedbackcircuitiscurrentsampling,voltagesummingnegativefeedback,andithasthecharacteristicsofhighinputandoutputimpedance.Theinputimpedanceishigh,whichisexactlywhatthepreviousstageconstantvoltageamplifiercircuitneeds,whichisbeneficialforthesignalvoltagetobesenttotheinputendofthepoweramplifierwithoutloss.Thehighoutputimpedancecanreducetheshuntoftheinternalresistancetothesignal,whichisconducivetoaddingtheoutputsignalcurrenttotheload.InFigure3,thepowersupplyvoltageisselectedas35V,anditsmagnificationisdeterminedbytheratioofthespeakertoR6.Figure3ConstantcurrentpoweramplifiercircuitdiagramV.Hi-FiIntegratedPowerAmplifierThefamousEuropeanSGS-THOMSONSTMicroelectronicshaslaunchedaHi-Fihigh-powerDMOSintegratedamplifiercircuitTDA7294.ThecircuitisshowninFigure4.Itintegratesthebestdesignofmodernpoweramplifiercircuit,combinestheadvantagesofbipolarsignalprocessingcircuitandpowerMOS,hasthecharacteristicsoflownoiseandlowdistortion;standbyandmutecircuitcompletelyeliminatestheimpactnoisecausedbypoweronandoff,andeliminatesspeakerprotectioncircuitoverheating,short-circuitcurrentprotectionandotherfunctionsmakeitsperformancemoreexcellent.ThisdeviceissuitableforhometheaterandHi-Fiamplifiers.Themainparametersare:VS(powersupplyvoltage)10~40V(maximumvoltagewithoutsignal50V);Io(peakoutputcurrent)10A;Po(RMScontinuousoutputpower)70Wwhenvs=35V8;vs=70Wwhen27V4;(effectivevalueofmusicoutputpower)100WwhenVS=38V8;100WwhenVS=29V4.Figure4Hi-FiIntegratedPowerAmplifierCircuitDiagramTheclosed-loopgainofthecircuitinFigure4is30dB.IncreasingR3canincreasethegain,andviceversa,buttheamplifiergainshouldbe24dB.TheamplifierhasthebestperformancewhenR1=R3.R7,C4andR5+R6,C3determinethestandbyandmutetimeconstants.Thelargerthevalue,thelongerthetime.Whenthecontrolterminalisconnectedtolowpotentialground,itismuteandstandby;whenthecontrolterminalisconnectedtoVS,because(R5+R6)R7,pin⑩risestoahigherpotentialthanpin⑨,andturnstoalowpotentialfirstwhenshuttingdown,whichmakesthestandbyandshutdownprocessesgooninasilentstate,ensuringthattheamplifieristurnedonandoffwithoutnoise.Figure5BTLPoweramplifierfinishedboardForhigh-powerprofessionalapplicationsfiledssuchasdancehalls,youcanchoosetheBTLpoweramplifierfinishedboardshowninFigure5.BothTDA7294areequippedwiththeirownprofessionalradiators.Whenvs=25V8,themaximumcontinuousoutputpowerreaches150W;when35V16,Themaximumcontinuousoutputpowerreaches170W.WeusedTDA7294standardapplicationcircuitandMarantzPM80andYAMAHAA-592tomakealisteningcomparison.Theformerisamid-pricedHi-FimachinewithaClassA,ClassAandBstatusswitch,andthelatterisa439.16dollarsclasswithAc-3inputAVpoweramplifier,audiosourceismusicfaxE60CD,speakerisTannerNo.5.ItturnsoutthatthesoundorientationofTDA7294hasadistinctiveEuropeanstyle,soft,mellow,delicate,andfullofbouncingfeeling.ItissimilartotheMarantzPM-80inClassAandBstatus,butthesoundfieldofPM-80isdeeperwhenworkinginpureClassA.ComparedwithYAMAHAA-592,thedifferenceislarger.ThelowfrequencyofA-592seemstobeslightlyimproved.Itsoundspowerful,butitisharderandthelinesareblurry.TDA7294issweetandnatural,withhigherresolution,reallylikelandscapepaintingdonewithsplashesofinkandfine-brushflowersandbirds(atechniqueofchineseink-painting),eachhasitsinfinitecharm.VI.ActiveSubwooferAmplifierAddsStandbyFunctionThiscircuitisanimprovementontheaudiocircuitusingtheintegratedcircuitTDA7294.ThecircuitdiagramisshowninFigure6.TDA729410pinhasamutefunction.WhentheexternalDCprovideshighlevel,theintegratedblockisintheworkingstate;whenthelowlevelisapplied,theintegratedblockisinthecut-offstate.Atthistime,thecircuitconsumeslittlepowerandIC114pinhasnooutput,thatis,standbyform.Thegeneralcircuitistoprovideahighleveltopin10tomakeitintheconductingstate,infact,thedevelopmentofthispinfunctioncanmeetsomespecialworkrequirements.Thiscircuitisbasedonthistoincreasethestandbyfunctionoftheactivesubwooferpoweramplifier,anditscircuitisreliableandresponsive.Figure6ActivesubwooferamplifieraddsstandbyfunctioncircuitdiagramVII.HighFidelityPowerAmplifierThecircuitisshowninFigure7.ThedrivestageadoptsTDA7294.Theinternaldrivestageandoutputstageofthechipusefieldeffecttubes,whicharepoweredby40V,andtheoutputpowercanreach70W(RL=8;THD=0.005%).Ithasadelicatetoneandanexcellentsenseofhearing.PoweroutputVT1,VT2adoptsShankenhigh-powerpairtube2SA1394,2SC3858.Thecircuitprincipleisasfollows:ThesignalisinputtotheTDA7294non-invertinginputpin③throughC1andR1.R7andR3,C3,C4ofICpin②formanegativefeedbacknetwork,theclosedloopgainofthisamplifierisabout34times.The⑨and⑩pinsarethestandbyandmuteterminalsrespectively.SincetheRCnetworktimeconstantofthe⑩pinislargerthanthatofthe⑨pin,theswitchingmachinesareallperformedundermutesatge,avoidingtheswitchingimpactsound,andC7isabootstrapcapacitor.Figure7High-fidelitypoweramplifierpromotedbyTDA7294Productionpoints:(1)InsulatingmicasheetsshouldbeaddedbetweenthemetalcapandtheheatsinkofTDA7294(themetalcapisconnectedtothepin⑧).(2)Thepowertransformerusesring-shaped300Wdouble20V,four50V/10000Ffiltercapacitors,two50V/100F,andtwo100V/0.1F.Thepowersupplypartshouldbetestedseparately,firstwithoutconnectingthepoweramplifier,measurewhetherthepositiveandnegativeoutputvoltageofthepowersupplyaresymmetrical,theerrorshouldbewithin0.6V.(3)Whentestingthemachine,forsafetyreasons,youshouldfirstusealowervoltagetest(suchas25V)withoutaddingasignal,andmeasuretheDCvoltageoftheoutputterminaltotheground.Normally,itshouldbewithin20mV.(4)R8,R9,R10,D1formthefinalbiascircuit.ThisbiasmakestheoutputtubesVT1andVT2notcutoffduringoperation,sothequiescentcurrentcanbesmall(about5mA).(5)Thepowertubeshouldbestrictlymatched(within3%)andgenuineproductsshouldbeselected.TheoutputresistanceR14isa5Wnon-inductivetype,andtheinductorLisformedbytightlywinding10turnsonR14withadiameterof1.5mmenameledwire.TDA7294uses60mmTimes,85mmTimes,20mm12-slotheatsink,andtheoutputpairtubeneedsaprofessionalheatsink.Thesectionswithhighcurrentontheprintedboardneedtobetin-rolled,whichisextremelybeneficialforthetransparencyandstrengthofthesound.Figure8PoweramplifierPCBpromotedbyTDA7294VIII.ClassABPowerAmplifierTDA7294integratedcircuitcanbeusedasahigh-fidelityaudioclassABpoweramplifier.Itcandrive4ohmor8ohmspeakers,andwhenconnectedtoan8ohmspeaker,itwillprovide50wattsofoutputpowerand0.1%THD.Figure9ClassABpoweramplifiercircuitdiagramYoumustinstallalargeenoughradiatorforTDA7294.Pin10isamuteinput,andpin9providesastandbymode.Muteshouldalwaysoccurwhenselectingstandbymode.TheIChasinternalthermalprotection,whichcausesmutereductionat145C,andtheamplifierentersstandbyat150C.TheTDA7294integratedcircuitheatsinkisinternallyconnectedtothenegativepowerrail.Ifthemoduleisinstalledinagroundedmetalenclosure,thentheICmustbeinsulatedfromtheheatsink.Ifnot,thenegativepowerrailwillbeshortedtoground.IX.Two-channelPowerAmplifierTDA7294high-powerintegratedcircuitICisspeciallydesignedforassemblinghigh-performanceaudioamplifiers.TwoTDA7294piecescanbeusedtomakeapowerfuldual-channelhigh-fidelitypoweramplifier.ThecircuitprincipleisshowninFigure10.TheoverallcircuitiscomposedoftwoTDA7294corecomponents,andtheperipheryincludessomeresistorsandcapacitors.Thecircuitsofthetwochannelsarealmostidenticalindesign.TheyallusethestandardcircuitofficiallyreleasedbyTDA7294,connectedtoanon-invertingamplifiercircuit,withavoltagegainof30.5dB,anoutputpowerofupto70Wperchannel,andadualpowersupplysymmetricalpowersupplyvoltage35V.Amongthem,Cl5andCl6areinputcouplingcapacitors.0.47Fisusedintheoriginalcircuit.Here,ifyouincreaseitto1F,youcanimprovethelow-frequencyresponseofthecircuit.Itisrecommendedtousepolypropylenespecialaudiocapacitors,suchasWIMAsMKT4seriescapacitors,itcangreatlyimprovethesoundresolution.R3andR4areinputresistances,whichdeterminetheinputimpedanceofTDA7294inthein-phaseamplificationstate.Here,22kisrelativelymoderate.Toolargeavaluecanreducetheburdenonthefront-endsignalsource,butitmayaffectthestabilityofTDA7294andmaketheoutputmidpointvoltagedriftincreased,toosmallvaluewillaffecttheresponseabilitytolowfrequency.ThetheoreticalvalueofthefeedbackresistorsR7andR8shouldbeequaltotheinputresistorsR3andR4,whichcanensurethebiascurrentbalanceoftheTDA7294inputdifferentialcircuitandreducesignaldistortion.ThefeedbackgroundresistanceR5,R6cooperateswithR7,R8tosetthecircuitgain.Here,thefeedbackDCblockingcapacitorsCl3andCl4areusedtoformACnegativefeedback,inhibitDCvoltageoutput,andprotectthespeaker.Figure10Two-channelpoweramplifiercircuitdiagramTDA7294hasastartmutefunction,andcooperateswithanexternalcircuittoachieveanon-impactsoundeffectwhenthepoweristurnedonandoff.R9,R1O,R11,Rl2,Cl7,Cl8andVD5,VD6intheschematicdiagramformanexternalmutecontrolcircuit.Delaytheenergizationofpins9and10ofTDA7294toachievethefunctionofsoftstart.Thepowersupplyrectifierfiltercircuitisalsoverysimple.Thefullbridgerectifiercircuitiscomposedof4EuropeanspeedrectifierdiodesVD1-VD4.CapacitorsC1andC2arethemainfiltercapacitors.Large-capacityandhigh-currentaudiofiltercapacitorsarerequired,suchasELNAsFORAUDIOseriesorBHCAerovoxindustrialgradecapacitors.DesignPCBisgenerallyabottleneckinamateurproduction,sothatmanyexcellentschematicdiagramshavenotbeentransformedintofinishedPCBsthatcanbeactuallyassembled.Here,thepopularProtel99sedesignsoftwareisusedtodrawtheprintedcircuitboardagainsttheschematicdiagram10,asshowninFigure11.The2mmthickFR-4board-baseddouble-sidedPCBisused,andthecopperfoilisthickenedto70mm,whichissuitableforhighcurrentpoweramplifiers.ThewholePCBtraceadoptsone-pointgroundingmethod,whicheffectivelyeliminatesgroundwireinterferencenoise.Insomehigh-currenttraces,tinplatingisalsoadoptedtoincreasetheadditionalcurrentcarryingcapacity.Thepowerinputandpoweroutputstructureuseshigh-currentscrewterminalstoensuresufficientover-currentcapabilityanddurabilityofrepeatedwiring.Figure11PrintedcircuitboardX.100WPowerAmplifierCircuitFigure12100WpoweramplifiercircuitdiagramcomposedofTDA7294Figure12isa100WpoweramplifiercomposedofamonolithicaudiopoweramplifierintegratedcircuitTDA7294.TDA7294includespre-opamplifier,finalpoweramplifier,temperatureprotection,shortcircuitprotection,mutecontrolandothercircuits.ThefinalstageadoptsbipolarDMOSpowertransistor,whichhasthecharacteristicsofhighoutputpower,bandwidth,lowdistortion,andgoodversatility.Theintegratedcircuitalsohasperfectanti-overload,anti-shortcircuitandtemperatureprotectioncircuitfunctions.Whenthechiptemperatureistoohigh,itautomaticallycutsofftheaudiosignaltoprotectthechipfromburningThepoweramplifiercircuitcomposedofTDA7294hasthecharacteristicsofsimpleperipheralcircuitandeasyproduction.Thecircuitinputimpedanceis20k,theinputsensitivityis750mV,thevoltagegainis32dB,thepowersupplyvoltagerangeis(25~40)V,andthequiescentcurrentis50mA.Whentheloadimpedanceis8,theoutputpoweris100W;whentheloadimpedanceis4,theoutputpowercanreach180W.Inactualproduction,TDA7294shouldbeequippedwithenoughheatsinks.Thesupportingpowercircuitshouldhavesufficientcapacity.Ifyouneedtoincreasethecircuitvoltagegain,youcanappropriatelychangetheratioofR3toR2,voltagegainA=201g(R3/R2)(dB).However,itisnotadvisabletoone-sidedlypursuethevoltagegainofthisstage.Excessivevoltagegaincaneasilycausecircuitself-excitation.Thesolutionistoincreasethevoltagegainofthepre-stage.I.DescriptionTDA2030Aisoneofthehigh-fidelityintegratedpoweramplifiers,andmanypoweramplifiercircuitsusethisintegrationmethod.TDA2030isalsoaHI-FIpoweramplifierintegratedblockusedbymanycomputeractivespeakers.Ithassimpleconnectionmethodandaffordableprice.Theratedpoweris14W.Thepowersupplyvoltageis6~18V.Theoutputcurrentislarge,theharmonicdistortionandthecrossoverdistortionaresmall(14V/4ohm,THD=0.5%).Ithasexcellentshortcircuitandoverheatprotectioncircuit.Thefollowingdescribesitsconnectionandapplicationcircuit.CatalogI.DescriptionII.Connection2.1SinglePowerConnection2.2DualPowerConnectionIII.ApplicationCircuit3.1OTLFormPowerAmplifier3.2OCLFormPowerAmplifier3.3BTLFormPowerAmplifier3.440WPowerAmplifierCircuit3.5High-fidelityActiveSpeakerCircuit3.625WBridgeLowFrequencyPowerAmplifierCircuitOrdering&QuantityII.ConnectionItsconnectionmethodisdividedintosinglepowersupplyanddualpowersupply:2.1SinglePowerConnectionFigure1TDA2030singlepowerconnectiondiagram2.2DualPowerConnectionFigure2TDA2030dualpowerconnectiondiagramIII.ApplicationCircuit3.1OTLFormPowerAmplifierOTLformpoweramplifier:singlepowersupply,outputcouplingcapacitor.TheR5(150k)andR4(4.7k)resistorsinthecircuitshowninFigure3determinetheclosed-loopgainoftheamplifier.ThesmallertheR4resistor,thegreaterthegain,buttoolargegaincaneasilycausesignaldistortion.Twodiodesareconnectedbetweenthepowersupplyandtheoutputterminaltopreventtheinductiveloadofthespeakerfromkickingbackandaffectingthesoundquality.ThecapacitorofC3(0.22uF)andtheresistanceofR6(1)areusedtocompensatetheinductiveload(speaker)toeliminateself-excitation.Thecircuitusesa36Vsinglepowersupplyandtheoutputpowerisabout20W.Figure3OTLtypepoweramplifiermadewithTDA2030A3.2OCLFormPowerAmplifierTheformoftheOCLpoweramplifieradoptsdualpowersuppliesandhasnooutputcouplingcapacitor.AsshowninFigure4,sincethelowfrequencyresponseoftheoutputcouplingcapacitorisimproved,itisahigh-fidelitycircuit.Thedualpowersupplyusesatransformerwiththemiddlepointoftheprimarycoilgroundedandtheupperandlowervoltagesaresymmetricalandequal.Afterrectificationandfiltering,a18Vdualpowersupplyisformed,andtheoutputpoweris20W.Figure4OCLtypepoweramplifiermadewithTDA20303.3.BTLFormPowerAmplifierThemainfeatureofBTLis:itiscomposedoftwoidenticalpoweramplifiers,andtheinputsignalsareinversetoeachother.Thein-phaseinputandtheinvertedinputoftheamplifierareactuallyusedtoensurethattheinputsignalsareinversetoeachother.Atthesametime,theamplitudesofthetwoinputsignalsshouldbethesame,sothatthebasicrequirementsoftheBTLcircuitformcanbemet.ThecircuitdiagramisshowninFigure5,whereR7(1k)andR8(33)resistorsdividethesignalandtheattenuationfactorisexactlythesameastheamplificationfactorofU1.TheattenuatedsignalisaddedtotheinvertinginputterminalofU2throughR5.Infact,twoopampscompleteasignalamplification,andtheactualmeasuredoutputlevelis1.5timeshigherthanthatofanintegratedcircuit.Thatis,theoriginaloutputpoweroftheopampis20W,andtheoutputpowerisnowabout50W.However,duetothecharacteristicsoftheBTLcircuit,whenchoosinganintegratedcircuit,usetwooperationalamplifiercircuitswiththesameparametersasmuchaspossibletoadjusttheinputsignalamplitude.Youcanuseanoscilloscopetoobservetheamplitudeofthetwoinputsignalsbyinputtingasinewave.Atthistime,adjustR7tomakethetwoinputsignalsTheamplitudeisthesametoensurethatthenonlinearsymmetrydistortionisminimizedwhileincreasingthepower.Figure5BTLtypepoweramplifiermadewithTDA2030A3.440WPowerAmplifierCircuitFigure6isa40WpoweramplifiercircuitmadebyTDA2030poweramplifierintegratedblockandBD907/908:Figure640WpoweramplifiercircuitmadebyTDA20303.5High-fidelityActiveSpeakerCircuitAhigh-fidelityactivespeakercircuitdesignedwithTDA2030,thecircuitdiagramisshowninFigure7.Usingdualpowersupply,addedhighandlowbassandvolumeadjustment.WhendesigningthePCB,thegroundwireshouldnotpassthroughthecomponentpinsasmuchaspossibletoreduceDCnoise.Figure7Highfidelityactivespeakercircuitdiagram3.625WBridgeLowFrequencyPowerAmplifierCircuitFigure825WbridgelowfrequencypoweramplifiercircuitThecircuitinFigure8usestwoTDA2030sconnectedtoformabridgecircuit,withthesamecircuitstructureandparametersonbothsides.Theintegratedcircuitontherightiscontrolledbytheintegratedcircuitontheleftthrougha22knegativefeedbackresistor,andviceversa.Thediode1N4001isusedtopreventthespeakerinductiveloadfromgeneratingovervoltageanddamagingthedevice.Theamplificationfactorofthecircuitcanbeadjustedbychangingthenegativefeedbackvoltageratiobetweentheoutputterminal(pin4)andtheinvertinginputterminal(pin2).

IDescriptionThisblogintroducesthepoweramplifierwithNE5532andLM1875Tasthecorecomponents.Thepoweramplifierwearediscussinghereisahigh-fidelitytwo-channelstereosubwooferpoweramplifier.Here,wewilldiscussitsmethodsandprocedures,schematicdesign,assemblyanddebugging,andspeakerproduction.Hopethisblogcanprovideagoodreferenceforbeginners.Figure1.LM1875CatalogIDescriptionIILM1875TandNE5532Overview2.1PowerAmplifierLM1875T2.2Pre-amplificationComponentNE5532IIICompositionofPowerSupplyIVAssemblyandDebuggingSpeaker4.1ElectricalInspection4.2BoxProductionVIntheEndOrdering&QuantityIILM1875TandNE5532OverviewFirst,weintroducethecorecomponentsthatwewilluse.Andthen,thebasiccharacteristicsofthesecomponents.Audiopoweramplifierisgenerallycomposedofthefollowingthreeparts:powersupply,pre-amplifierandpost-amplifier.Here,wewillusehigh-efficiencyHI-FIpowerintegratedchipLM1875Tasthecoreoriginal.LM1875Tadoptsapositiveandnegative15Vdualpowersupply,theleft,andrightchannelsworkinOCLmode,andthebassworksinBTLmode.AsfarasthecharacteristicsofLM1875Tareconcerned,ithasthecharacteristicsofgoodsoundquality,goodfrequencyresponse,lowcostandrelativelysimplecircuit.Inaddition,thepre-amplifierpartusestheNE5532integratedoperationalamplifier.2.1PowerAmplifierLM1875TLM1875Thasexcellentperformance.Manyluxury-lookingactivespeakers,mid-rangepoweramplifiers,andsubwoofersonthemarketuseLM1875T.ThepoweramplifiercircuitcomposedofLM1875Tchiphasthefollowingcharacteristics:Theoutputpowerislarge,themaximumpowercanreachabout20W;Thestaticcurrentissmall,theloadcapacityisstrong,andthedynamiccurrentislarge,whichcandrive4~8speakers;Thecircuitissimple,easytomanufactureandlowcost;Withaninternalprotectioncircuit,itisahigh-fidelitypoweramplifiercomponentwithstableperformance.Theblogdesignofthisarticleisadual-channelstereosubwooferpoweramplifier,butLM1875Tisamono-channelpoweramplifierintegratedcircuit,sothedual-channelOCLworkingmodeusesoneLM1875Tforeachchannel.SincethebassworksinBTLmode,wehavetousetwopieces.LM1875Thas5pins.Theyarepositivepowersupply,negativepowersupply,positiveinput,reverseinput,andoutput.ThecircuitisshowninFigure2.Figure2.LM1875Circuit2.2Pre-amplificationComponentNE5532Beforethepoweramplifiercircuit,itisgenerallynecessarytoaddapreamplifier.Thepurposeofthisistoamplifythevoltageofvariousinputweakelectricalsignals.Inordertoensurethattheoutputelectricalsignalhashighfidelity,thepre-amplifierisNE5532.NE5532isahigh-performance,low-noise,dualoperationalamplifierintegratedcircuit.Comparedwithmanystandardopamps,NE5532hasbettersoundperformance,excellentoutputdrivecapability,relativelyhighsmallsignalbandwidth,andlargepowersupplyvoltagerange.Therefore,itisverysuitableforhigh-qualityandprofessionalaudioequipment,instruments,controlcircuitsandtelephonechannelamplifiers.Whenusedforaudioamplification,thetoneiswarmandhighfidelity.ThefunctionalblockdiagramofNE5532isshownasinFig.3.Figure3.NE5532FunctionalBlockDiagramIIICompositionofPowerSupplyLM1875Tadoptsapositiveandnegative15Vdualpowersupply.TheoperatingvoltageofNE5532isalso15V.Weneedtostepdownthemainspowerto15Vthroughastep-downtransformer,thenrectifyitthroughtherectifierbridgeKBL406,filteritthroughalargecapacitor,anddirectlysupplyittothepoweramplifier.Inthisway,largeroutputpowerisobtained.After7815and7915,theregulatedoutput15VisusedasthepowersupplyofthepreamplifierNE5532.ThecompositionofthepowersupplyisshowninFigure4.Figure4.PowerCircuitFigure5.PowerAmplifierCircuitBoardIVAssemblyandDebuggingSpeakerWhenstartingthecircuitinstallation,firstcheckthecircuitboardagainstthecircuitdiagram.Forexample,checkwhetherthemaincomponentsareinstalledcorrectly,andwhetherthesolderjointshavemissingsolderingorfalsesoldering.Thenturnonthepowertodebugthecircuit,andmakespeakersafterthedebuggingiscompleted.TheactualproductionisshowninFigure6.Figure6.PhysicalShootingPic4.1ElectricalInspectionUseanACsignalgeneratortoaddatinysinusoidalsignaltothesignalinput.Then,usetheoscilloscopetomeasurethethreeoutputsignalsofthepoweramplifierboard.Atthistime,observewhetherthesinemeetstherequirementsandwhethertheparametersinthetestarerelativelystable.Then,connecttwofull-rangespeakerstotheleftandrightchannels,andconnectawoofertothebassoutputport.Atthistime,addthesongsignaltocarefullycheckwhetherthethreespeakersareworkingproperlyandthesoundisgood.Iftheabovestepsarewellexpressed,thenproceedtothenextstep.4.2BoxProductionThekeytomakingspeakersistheselection,sizeandothersteps.Intheexperiment,weusedthelaminatesinthelaboratoryforsplicingandassembly.First,drawasketch.Thepaintingisdividedonthreedifferentsubstrates,andthenmadeintotwopartsrespectively.Afterdrilling,polishing,splicingandbonding,thecompletedcircuitpartsareinstalledintheirrespectiveparts.Then,wedividetheentirepoweramplifierintothreeparts.Twosatellitespeakers,aswellasawooferandpoweramplifierboard.Thesethreepartstogetherformacomplete2.1subwooferpoweramplifier.Here,thereisaplacethatneedsspecialattention.Whenmakingthebasspartofthecabinet,theimpactofvibrationshouldbefullyconsidered.Therefore,wehavetodesigndampingcomponents.VIntheEndAftertheinstallationisnormal,connectthemusicsignalsourceandlistentothemusiceffect.Thesoundreproducedbythiscircuithasastrongsenseofhierarchy,aclearsenseoforientation,andanobvioussenseofspaceanddistance.Inaddition,thesoundimageorientationisclear,thewidthisoutstanding,andthesounddynamicrangeislarge,givingpeoplearealfeeling.IntroductionLM3886isahigh-performanceaudiopoweramplifier.ItexhibitsextremelylowTHD+Nvaluesof0.03%attheratedoutputintotheratedloadovertheaudiospectrum,andprovidesexcellentlinearitywithanIMD(SMPTE)typicalratingof0.004%.Itisverysuitablefortheenthusiastswhopursuebothbeautifulsoundqualityandstrongvolume.ThisarticleintroducesseveralpracticalapplicationsofLM3886inhometheatersystems.ThisisatechnicalexaminationvediooftheLM3886Amplifier.CatalogIntroductionCatalogIHighQualityDual-channelPowerAmplifierIIPowerfulBTLPowerAmplifierIIISubwooferSpeakerOrdering&QuantityIHighQualityDualChannelPowerAmplifierLM3886outputsnearly70Wpoweratratedvoltageandthepeakpoweris150W.Thedualchannelpoweramplifieradoptssimpleandtypicalcircuit,whichcanreplaceavarietyofHI-FIpoweramplifier,andissuitablefortheleftandrightmainchannelofpoweramplifierinhomecinema.ThewholecircuitisinstalledonthesamePCB.EachofthetwoLM3886sisequippedwithaspecialaluminumradiator(length140,thickness50,height75(mm)),whicharefixedonbothsidesofthePCBtofacilitateheatdissipation.Thepowertransformercanchoosedouble24~28V,3~5A.IIPowerfulBTLPowerAmplifierApureBTLbridgeamplifieriscomposedofanoperationalamplifierNE5532,anLM3886in-phaseamplifierandanLM3886invertingamplifier,whichcaneasilyoutputmorethan200Wundistortedpower.Itcanbeusedindancehalls,karaoke,theatersandotheroccasions.Thiscircuitcankeepthesoundqualitynaturalandsmoothwhenplayingatlowvolume.BTLPoweramplifiercircuitisshowninFigure1.Onecircuitboardforeachchannel,withindependentrectification.Thesizeoftworadiatorsis140mminlength,50mminthicknessand100mminheight.Figure1.BTLPowerAmplifierCircuitIIISubwooferSpeakerFigure2isthecircuitofahouseholdsubwooferspeaker.Figure2.circuitofsubwooferspeakerInthepicture,theLinkwitzactivecompensatoraccuratelycontrolsthecenterfrequencyf1ofthecompensationpeakanditsQvalue,sothattheclosedbox(seeFigure3)withanaturalcornerfrequencyabout50Hzandthefrequencyresponsecurve(seeFigure4)extendsdownflatly.Thelowend-3dBpointreaches25Hz.Figure3.ClosedboxFigure4.frequencyresponsecurveInFigure4,curveAisnaturalfrequencyresponse;Biscompensationcurve;andCissystemfrequencyresponse.Theturningfrequencyofthelow-passfilteriscontinuouslyadjustablefrom80Hzto200Hz,sothattheactivesubwoofercanmatchthereadersdualchannelspeakerwithdifferentfrequencylimits.TheloudspeakerusessilverfluteYD310-43.Thebasindiameteris310mm.Themagnetdiameteris158mm.Theresonancefrequencyis25Hz.Q=0.35.Thecontinuouspoweris50W,andthesensitivityisashighas95dB.ComparedwiththeHiviS8unitwithasensitivityof88dB,thesensitivitydifferencebetweenthetwois7dB.Fortheclosedbox,theoutputsoundpressureofYindiYD310-43whenitinput50WisequivalenttotheoutputofHiviS8unitwhenitinput200W.YindicanalsobereplacedbytheBlueWhaleYD310-8XA.Insteadofthebassreflexwithpoortransientperformanceandlowsensitivity,itisbettertousethesimplestclosedbox.Theboxshallbesolidandairtight,filledwithglassfibercottonoracryliccottonforwarmthabsorption,andthesmallcavityatthebottomoftheboxshallbeusedtoinstallthecircuitpart.Forthesakeofsimpleinstallation,allcircuitsareinstalledonthePCB.ThePCB,radiator,switchandI/Oconnectorarefixedonthemetalpanel,andthenfixedonthespeakerwith6screws.Then,itcanworkafterconnectingtohornandtransformer.Connectthesubwooferactivespeakerwiththehomestereospeakertoforma3Dplaybacksystem.

what is a common use for point contact diodes?

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