模拟电子线路-[英文课件]--杨凌【英文】机械工业出版-chpt-3

TeachingMaterialsofAnalogCircuits,Chap3,Chapter2TheBipolarJunctionTransistorandTheBasicBJTAmplifiers,2.0PreviewThedevelopmentofthesilicontransistorbyBardeen,Brattain,andSchockleyatBellTelephoneLaboratoriesinthethelate1940sstartedthefristelectronicsrevolutionofthe1950sand1960s.Thisinventionledtothedevelopmentofthefristintegratedcircuitin1958andtotheoperationaltransistoramplifier(opamp),whichisoneofthemostwidelyusedelectroniccircuits.,2.1BasicBipolarJunctionTransistor,Thebipolarjunctiontransistor(BJT)hasthreeseparatelydopedregionsandcontainstwoPNjunction.Thebasicprincipleisthatthevoltagebetweentwoterminalscontrolsthecurrentthroughthethridterminal.Theoperationofthetransistoristhereforetotallydifferentfromthatoftwoback-to-backdiodes.Currentinthetransistorisduetotheflowofbothelectronsandholes,hencethenamebipolar.一、TransistorStructures，SymbolsOneimportantpointisthatthedeviceisnotsymmetricalelectrically.Thisasymmetryoccursbecausethegeometriesoftheemitterandcollectorregionsarenotthesame(thewidthofthebasemustbeverynarrow,normallyintherangeof,2.1BasicBipolarJunctionTransistor,tenthsofamicrometer106m).andtheimpurityconcentrationsinthethreeregionsaresubstantiallydifferent.Forexample,theimpuritydopingconcentrationsintheemitter,collector,andbasemaybeontheorderof1019,1017,and1015cm3.,figure2.1,2.1BasicBipolarJunctionTransistor,Therefore,eventhoughbothendsareeitherP-typeorN-typeonagiventransistor,switchingthetwoendsmakesthedeviceactindrasticallydifferentways.,figure2.2Crosssectionofaconventionalintegratedcircuitnpnbipolartransistor,2.1BasicBipolarJunctionTransistor,二、TransistorCurrentsIfthetransistorisusedasanamplifyingdevice,thebase-emitterjunctionisforwardbiasedandthebase-collectorjunctionisreversebiased,inaconfigurationcalledtheforward-activeoperatingmode,orsimplytheactiveregion.TheformingofthreecurrentsFigure2.3showsanidealizedNPNbipolartransistorbiasedintheforward-activemode.2.CurrentRelationships,2.1BasicBipolarJunctionTransistor,IE=IEp+IEn,IB=IEp+(IEnICn1)ICBO,(2-1),IC=ICn1+ICBO,figure2.3,IE=IC+IB,2.1BasicBipolarJunctionTransistor,IB=IEp+(IEnICn1)ICBO,2.1BasicBipolarJunctionTransistor,figure2.4,三、TransistorModelsTheMathematicalModel,2.1BasicBipolarJunctionTransistor,figure2.5,(c),EarlyEffectBase-WidthModulationEffect,2.1BasicBipolarJunctionTransistor,2.1BasicBipolarJunctionTransistor,(b)CutoffRegionJeandJcbothreversebiased.IB=0,IC=ICEO0;(IE=0,IC=ICBO,IB=ICBO)(c)SaturationRegionJeandJcbothforwardbiased.ICIB;ICIBVBE(sat)VBE(on)=0.7V;VCE(sat)0.3V,figure2.8,2.1BasicBipolarJunctionTransistor,(d)BreakdownRegionVCEVCBJcAvalanchebreakdownV(BR)CEOV(BR)CBOV(BR)EBOV(BR)CBOV(BR)CEOV(BR)EBO,2.1BasicBipolarJunctionTransistor,Cbc、Cbe,V(BR)CBOV(BR)CESV(BR)CERV(BR)CEO,2.1BasicBipolarJunctionTransistor,3.TheDcEquivaientcircuit,VCE=VCCICRc,(a),figure2.10,2.1BasicBipolarJunctionTransistor,4.TheSmall-SignalEquivaientcircuit,2.1BasicBipolarJunctionTransistor,figure2.11,iB=IBQ+ibvBE=VBEQ+vbeiC=ICQ+icvCE=VCEQ+vcevBE=f1(iB,vCE)iC=f2(iB,vCE),(a),2.1BasicBipolarJunctionTransistor,(214),(213),hie()hrehfehoe(S),2.1BasicBipolarJunctionTransistor,figure2.12,re0,2.1BasicBipolarJunctionTransistor,四、TheMethodofAnalysis1.Computer-AidedAnalysis2.GraphicalAnalysis(DcAnalysis;AcAnalysis)3.EngineeringApproximation(DcAnalysis;AcAnalysis)五、BasicTransistorApplications1.CurrentSource,figure2.13,2.1BasicBipolarJunctionTransistor,2.Switch,Figure2.14showsabipolarcircuitcalledaninverter,inwhichthetransistorinthecircuitisswitchedbetweencutoffandsaturation.Theload,forexample,couldbeamotor,alight-emittingdiode,orsomeotherelectricaldevice.,3.Amplifier,Inordertocreatalinearamplifier,wemustkeepthetransistorintheforward-activemode,establishaQ-pointnearthecenteroftheloadline,andcouplethetime-varyinginputsignaltothebase.,2.2PreviewofAmplifier,Linearamplifiersimplythatwearedealingwithanalogsignals.Themagnitudeofananalogsignalmayhaveanyvalueandvarycontinuouslywithrespecttotime.Alinearamplifierthenmeansthattheoutputsignalisequaltotheinputsignalmultipliedbyaconstant,wherethemagnitudeoftheconstantofproportionalityis,ingeneral,greaterthanunity.Alinearamplifieriscapableofproducingsignalpowergain;thatis,thepowerintheoutputsignalisgreaterthanthepowerintheinputsignal.Wewillinvestigatethesourceofthis“extra”power.一、TheConceptofAmplifierTime-varyingsignalsfromaparticularsourceveryoften,2.2PreviewofAmplifier,needtobeamplifiedbeforethesignaliscapableofbeing“useful”.Forexample,Figure2.15showsasignalsourcethatistheoutputofacompactdiscsystem.Thatsignalconsistofasmalltime-varyingvoltageandcurrent,whichmeansthesignalpowerisrelativelysmall.Thepowerrequiredtodrivethespeakersislargerthantheoutputsignalfromthecompactdisc,sothecompactdiscsignalmustbeamplifiedbeforeitiscapableofdrivingthespeakersinorderthatsoundcanbeheard.Otherexamplesofsignalsthatmustbeamplifiedbeforetheyarecapableofdrivingloadsincludetheoutputofamicro-phone,voicesignalsreceivedonearthfromanorbitingmannedshuttle,andvideosignalsfromanorbitingweathersatellite.,2.2PreviewofAmplifier,figure2.15,Figure2.15suggestthattherearetwotypesofanalysesofamplifierthatwemustconsider.Thefirstisadcanalysisbecauseoftheapplieddcvoltagesource,andthesecondisatime-varyingoracanalysisbecauseofthetime-varyingsignalsource.,2.2PreviewofAmplifier,二、PerformanceIndexofAmplifier,1.InputImpedance,2.2PreviewofAmplifier,3.Gain,FourModels,2.OutputImpedance,2.2PreviewofAmplifier,(a)Voltageamplifier,RiRs(Ri)RoRL(Ro0),2.2PreviewofAmplifier,(b)Currentamplifier,RiRs(Ri0)RoRL(Ro),2.2PreviewofAmplifier,(c)Transresistanceamplifier,RiRs(Ri0)RoRL(Ro0),4.Bandwidth,(d)Transconductanceamplifier,RiRs(Ri)RoRL(Ro),figure2.17,2.2PreviewofAmplifier,5.（TotalHarmonicDistortion）,BW=fHfL(223),2.2PreviewofAmplifier,三、BasicTransistorAmplifierConfigurationsAswehaveseen,thebipolartransistorisathree-terminaldevice.Threebasicsingle-transistoramplifierconfigurationscanbeformed.Dependingonwhichofthethreetransistorterminalsisusedassignalground.Thesethreebasicconfigurationsareappropriatelycalledcommomemitter,commoncollector,andcommonbase.asshowninfigure2.19,2.2PreviewofAmplifier,Whichconfigurationoramplifierisusedinaparticularapplicationdependstosomeextentonwhethertheinputsignalisavoltageorcurrentandwhetherthedesiredoutputsignalisavoltageorcurrent.Thecharacteristicsofthethreetypesofamplifierswillbedeterminedtoshowthecondtionsunderwhicheachamplifierismostuseful.Eachofthethreebasictransistoramplifierscanbemodeledasatwo-portnetworkinoneoffourconfigurationsasshowninfigure2.17.Weshouldnotethat,Althoughoneconfigurationsshowninfigure2.17maybepreferableforagivenapplication,anyoneofthefourcanbeusedtomodelagivenamplifier.,2.2PreviewofAmplifier,四、Common-EmitterAmplifiers,figure2.20,1.CircuitStructure,2.DcChannelandAcChannel,2.2PreviewofAmplifier,figure2.21,(a),(b),Rb=Rb1Rb2,2.2PreviewofAmplifier,figure2.22,3.ReferencePerformance,2.2PreviewofAmplifier,Thepowerprvoidedbythedcvoltagesourceis:,Thepowerdissipatedbytheresistor(RC)is:,ThepowerdissipatedintheTransistoris:,PD=VCCICQ=(VCEQ+ICQRC)ICQ=VCEQICQ+ICQ2RC=PL+PC,2.3GraphicalAnalysisofAmplifier,Thegraphicaltechniquecanprovideanintuitiveinsightintothebasicoperationoftransistoramplifiers.,一、DCAnalysis,1.Objective:DetermineQ-point(VBEQ、IBQ、VCEQ、ICQ),2.Object:DcChannel,2.3GraphicalAnalysisofAmplifier,3.Procedure,VCC=IBRb+VBE,VCC=ICRc+VCE,figure2.23,IC,2.3GraphicalAnalysisofAmplifier,二、ACAnalysis,1.Objective:DetermineAV、Vom、Nonlineardistortion,2.Object:AcChannel,Procedure(1)(2)(3),2.3GraphicalAnalysisofAmplifier,2.3GraphicalAnalysisofAmplifier,三、TheImportanceofQ-Point,2.4EquivalentCircuitAnalysisofAmplifier,一、DCAnalysis,1.Objective:DetermineQ-point(VBEQ、IBQ、VCEQ、ICQ),2.Object:DcChannel,Procedure(1)SingleBaseResistorBiasing,figure2.26,2.4EquivalentCircuitAnalysisofAmplifier,(2)VoltageDividerBiasing,figure2.27,ICQ=IBQ,VCEQ=VCCICQRcIEQReVCCICQ(Rc+Re),Rb=Rb1Rb2,2.4EquivalentCircuitAnalysisofAmplifier,(1+)Re10Rb,VEQ=VBBVBEQ,IBQ=ICQ/VCEQVCCICQ(Rc+Re),(3)ComparedTheTwoBiasing,T=300K,=100,VBE(on)=0.7V,ICBO=1012AIBQ=19.63A,ICQ=1.96mA,VCEQ=2.08V,T30oC,=130,VBE(on)=0.625V,ICBO=81012AIBQ=19.91A,ICQ=2.59mA,VCEQ=0.82V,+6V,270k,2k,2.4EquivalentCircuitAnalysisofAmplifier,Themostimportantadvantageofinclude-inganemitterresistoristhatitstabilizestheQ-pointwithrespecttotemperature.,ExampleExample2.1Objective:Analyzeacircuitusingavoltagedividerbiascircuit,anddeterminethechangeintheQ-pointwithavariationinwhenthecircuitcontainsanemitterresistor.Forthecircuitgiveninfigure2.27.LetRb1=56k，Rb2=12.2k，Rc=2k，Re=0.4k，VCC=10V,VBE(on)=0.7V,2.4EquivalentCircuitAnalysisofAmplifier,and=100.Solution:,ICQ=IBQ=10021.6=2.16mA,VCEQ=VCCICQRcIEQRe4.81V,Rb=Rb1Rb2=5612.210k,IEQ=(1+)IBQ=10121.6=2.18mA,Theseresultsshowthatthetransistorisbiasedintheactiveregion.Ifthecurrentgainofthetransistorweretodecreaseto=50,2.4EquivalentCircuitAnalysisofAmplifier,orincreaseto=150,weobtainthefollowingresults:,Fora3:1ratioin,thecollectorcurrentandcollector-emittervoltagechangebyonlya1.29:1ratio.Comment:ThevoltagedividercircuitofRb1andRb2canbiasthetransistorinitsactiveregionusingresistorvalueinthelowkilohamrange.Incontrast,singleresistorbiasingrequiresaresistorinthemegohmrange.Inaddition,thechangeinICQandVCEQwithachangeinhasbeensubstantiallyreducedcomparedtothechangeshowninfigure2.26.Includingan,2.4EquivalentCircuitAnalysisofAmplifier,emitterresistorhasRetendedtostabilizetheQ-point.ThismeansthatincludingtheemitterresistorhelpstostabilizetheQ-pointwithrespecttovariationsin.Example2.2Objective:Designabias-stablecircuit.Considerthefollowingcircuit.LetVCC=9V,VBE(on)=0.7V，=100,chooseRc、ReanddetermineRb1、Rb2suchthatthecircuitisbiasstableandthatICQ=1mA,VCEQ=4.5V.Solution:(1)Typically,LetVEQ=0.2VCC=1.8VthenRe=VEQ/IEQVEQ/ICQ=1.8/1=1.8k(2)LetI1=10IBQ=10ICQ/=0.1mAthenRb1+Rb2=VCC/I1=90k,2.4EquivalentCircuitAnalysisofAmplifier,(3)VCEQVCCICQ(Rc+Re),Comment:TheQ-pointinthisexampleisnowconsideredstabilizedagainstvariationsin,andthevoltagedividerresistorRb1andRb2havereasonablevaluesinthekilohmrange.,二、ACAnalysis,2.4EquivalentCircuitAnalysisofAmplifier,2.Object:AcChannel,Procedure,figure2.28,2.4EquivalentCircuitAnalysisofAmplifier,figure2.29,(227),2.4EquivalentCircuitAnalysisofAmplifier,三、CECircuitwithEmitterResistor1、CircuitStructure2、DCAnalysisThesameasforthefigure2.27.3、ACAnalysis,2.4EquivalentCircuitAnalysisofAmplifier,figure2.30,2.4EquivalentCircuitAnalysisofAmplifier,VoAV=Vi,Nowlet,sconsidertheresistorrce.,2.4EquivalentCircuitAnalysisofAmplifier,figure2.31,2.4EquivalentCircuitAnalysisofAmplifier,Where,2.4EquivalentCircuitAnalysisofAmplifier,Example2.3Objective:Determinethesmall-signalvoltagegainAV、inputresistanceRi、outputresistanceRoofacommonemittercircuitwithanemitterresistor.Forthecircuitinfigure2.32.thetransistorparametersareVBE(on)=0.7V，=150andVA=100V.Solution:(1)DCSolution:,figure2.32,Rb=Rb1Rb2=561511.83k,2.4EquivalentCircuitAnalysisofAmplifier,rceVA/ICQ=100/1.1785.47k(81.97k),ICQ=IBQ=1507.81031.17mA,ACSolution:Thesmall-signalhybrid-parametersaredeterminedtobe,IEQ=(1+)IBQ=1517.81031.18mA,2.4EquivalentCircuitAnalysisofAmplifier,Ri=Rbrbe+(1+)Re1=11.833.33+(1+150)0.024.13k(4.1k),RoRcRo=8.2102.47.59k(7.57k),AssumethatVA=,then,RoRc=8.2k,2.4EquivalentCircuitAnalysisofAmplifier,Comment:Themagnitudeofthesmall-signalvoltagegainissubstantiallyreducedwhenanemitterresistorisincluded.Discussion:Theamplifiergainisnearlyindependentofchangesinthecurrentgainparameter.Thisfactisshowninthefollowingcalculations:Table2.2,Inadditiontogaininganadvantageinstabilitybyincludinganemitterresistance,wealsogainanadvantageintheloadeffect.Thereislessloadingeffectbecausetheinputresistancetothebaseofthetransistorishigherwhenanemitterresistorisincluded.,2.5Commom-Collector(Emitter-Follower)Amplifier,Thesecondtypeoftransistoramplifiertobeconsideredisthecommon-collectorcircuit.Anexampleofthiscircuitconfigur-ationisshowninfigure2.33.Asseeninthefigure,theoutputsignalistakenoffoftheemitterwithrespecttogroundandthecollectorisconnecteddirectlytoVCC.SinceVCCisatsignalgroundintheacequivalentcircuit,wehavethenamecommon-collector.Themorecommonnameforthiscircuitisemitterfollower.Thereasonforthisnamewillbecomeapparentasweproceedthroughtheanalysis.一、CircuitStructure,2.5Commom-CollectorAmplifier,figure2.33,二、DcAnalysis,Rb=Rb1Rb2,IEQ=(1+)IBQ,VCEQ=VCCIEQRe,2.5Commom-CollectorAmplifier,三、AcAnalysis,figure2.34,2.5Commom-CollectorAmplifier,Ri=RbRi=Rbrbe+(1+)RL(233),figure2.35,2.5Commom-CollectorAmplifier,四、TheCommon-CollectorAmplifierUtilizingTheDarlingtonConfiguration,1、TheDarlingtonConfiguration,figure2.36,2.5Commom-CollectorAmplifier,2、TheCompositionalPrincipleofTheDarlingtonPair(1)(2)(3),Weseefromequations(2-35)thattheoverallgainoftheDarlingtonpairislarge.Atthesametime,theinputresistancetendstobelarge,becauseofthemultiplication.,(b),(a),figure2.37,2.5Commom-CollectorAmplifier,figure2.38,(a),3、TheEmitter-FollowerUtilizingtheDarlingtonConfiguration,(b),2.5Commom-CollectorAmplifier,figure2.39,五、TheApplicationofTheEmitter-Follower,2.5Commom-CollectorAmplifier,Atfirstglance,atransistoramplifierwithavoltagegainessentiallyof1maynotseemtobeofmuchvalue.However,theinputandoutputresistancecharacteristicsmaketheemitter-followerexremelyusefulinmanyapplications.Theinputresistanceoftheemitter-followerlookingintothebaseissubstantiallylargerthanthatofthesimplecommon-emittercircuit.Becauseofthis,theemitter-followerisoftenusedastheinputstageofamultistageamplifier.,2.5Commom-CollectorAmplifier,Theverylowoutputresistancemakestheemitter-followeractalmostlikeanidealvoltagesource,sotheoutputisnotloadeddownwhenusedtodriveanotherload.Becauseofthis,theemitter-followerisoftenusedastheoutputstageofamultistageamplifier.Theemitter-followercircuitissometimesreferredtoasanimpedancetransformer,sincetheinputimpedanceislargeandtheoutputimpedanceissmall.,2.6Commom-BaseAmplifier,Thethirdamplifiercircuitconfigurationisthecommon-basecircuit.Todeterminethesmall-signalvoltageandcurrentgains,andtheinputandoutputimpedances,wewillusetheSamehybrid-equivalentcircuitforthetransistorthatwasUsedpreviously.Thedcanalysisofthecommom-basecircuitisessentiallythesameasforthecommon-emittercircuit.一、CircuitStructure,2.6Commom-BaseAmplifier,figure2.40,二、DcAnalysisThesameasforthecommon-emittercircuit.三、AcAnalysis,(a),(b),2.6Commom-BaseAmplifier,figure2.41,2.6Commom-BaseAmplifier,Figure2.42showsthecircuitusedtocalculatetheoutputresistance.Theindependentsourcevshasbeensetequaltozero.Thisimpliesthat,figure2.42,Ib=0Ib=0.Consequently,theoutputresistancelookingbackintotheoutputterminalsisthen,Ro=rcbRcRc(239),2.7TheThreeBasicAmplifierSummaryandComparison,Thebasicsmall-signalcharacteristicsofthethreesingle-stageamplifierconfigurationsaresummarizedinTable2.1.Table2.1CharacteristicsofthethreeBJTamplifierconfigurations,2.7TheThreeBasicAmplifierSummaryandComparison,Forthecommon-emittercircuit,thevoltageandcurrentgainsaregenerallygreaterthan1.Fortheemitter-follower,thevoltagegainisslightlylessthan1,whilethecurrentgainisgreaterthan1.Forthecommon-basecircuit,thevoltagegainisgreaterthan1,whilethecurrentgainislessthan1.Theinputresistancelookingintothebaseterminalofacommon-emittercircuitmaybeinthelowkilohmrange;inanemitterfollower,itisgenerallyinthe50to100krange;Theinputresistancelookingintotheemitterofacommon-basecircuitisgenerallyontheorderoftensofohms.Theoverallinputresistanceofboththecommon-emitterandemitter-followercircuitscanbegreatlyaffectedbythebiascircuitry.,2.7TheThreeBasicAmplifierSummaryandComparison,Theoutputresistanceoftheemitter-followerisgenerallyintherangeofafewohmstotensofohms.Incontrast,Theoutputresistancelookingintothecollectorterminalofthecommon-emitterandcommon-basecircuitsisveryhigh.Inaddition,Theoutputresistancelookingintotheoutputterminalofthecommon-emitterandcommon-basecircuitsisastrongfunctionofthecollectorresistance.Forthesecircuits,theoutputresistancecaneasilydroptoafewkilohms.Thecharacteristicsofthesesingle-stageamplifierswillbeusedinthedesignofmultistageamplifiers.,2.8MultistageAmplifier,Inmostapplications,asingletransistoramplifierwillnotbeabletomeetthecombinedspecificationsofgivenampli-ficationfactor,inputresistance,andoutputresistance.Forexample,therequiredvoltagegainmayexceedthatwhichcanbeobtainedinasignaltransistorcircuit.Transistoramplifiercircuitscanbeconnectedinseries,orcascaded.asshowninfigure2.45.Thismaybedoneeithertoincreasetheoverallsmall-signalvoltagegainortopro-videanoverallvoltagegaingreaterthan1,withaverylowoutputresistance.,2.8MultistageAmplifier,Theoverallvoltagegainorcurrentgain,ingeneral,isnotsimplytheproductoftheindividualamplificationfactors.Forexample,thegainofstage1isafunctionoftheinputresistanceofstage2.Inotherwords,loadingeffectsmayhavetobetakenintoaccount.,2.8MultistageAmplifier,Wemaystarttheanalysisattheoutputandworkbacktotheinput,orstartattheinputandworktowardtheoutput.一、AcAnalysisThesmall-signalvoltagegainis,2.8MultistageAmplifier,二、CoupledModes1.CapacitivelyCoupled,figure2.46,TransformerCoupled3.DirectlyCoupled,2.8MultistageAmplifier,figure2.47,VCQnVCQ3VCQ2VCQ1,Level-Shiftingfigure2.47DriftDifferentialAmplifier,figure2.48,2.8MultistageAmplifier,三、CombinationAmplifier,(a)CE-CB,figure2.49,(b)CC-CE,(c)CC-CB,2.8MultistageAmplifier,四、CommonEmitterAmplifierwithActiveLoad,figure2.50,Summary,1.Inthischapter,weconsideredthebasiccharacteristicsandpropertiesofthebipolartransistor,whichisathreedevicethathasthreeseparatelydopedsemiconductorregionsandtwoPNjunctions.2.Themodesofoperationofabipolartransistoraredeterminedbythebiasesappliedtothetwojunctions.Thefourmodesare:forwardactive,cutoff,saturation,andinverseactive.Intheforward-activemode.theB-EjunctionisforwardbiasedandtheB-Cjunctionisinversebiased,andthecollectorandbasecurrentsarerelatedbythecommom-emittercurrentgain.Therelationshipisthesamefor,Summary,bothNPNandPNPtransistors,aslongastheconventionalcurrentdirectionsaremaintained.Whenatransistoriscutoff,allcurrentsarezero.Int