Chapter1:

SemiconductorDiodes全套PPT課件DiodesAdiodeisa2-terminaldevice.Adiodeideallyconductscurrentinonlyonedirection.21.2SemiconductorMaterialsCommonmaterialsusedinthedevelopmentofsemiconductordevices:Silicon(Si)Germanium(Ge)GaAs3Fig.1.3Atomicstructureof(a)silicon;(b)germanium;and(c)galliumandarsenic.Fig.1.4Covalentbondingofthesiliconatom.1.3CovalentBondingandIntrinsicMaterialsThesingle-crystalformedbypuresemiconductormaterialsiscalledintrinsicsemiconductor.IntrinsicSemiconductorsHoles:VacanciesinthecovalentbondElectron-holepairs:afreeelectronandaholeisgeneratedfromthecovalentbondbythermalenergyMovementofHoles:bymovementofcovalentelectronsfromadjacentcovalentbondsTwotypesofchargedparticles(Intrinsiccarriers)inasemiconductorfreeelectronsholesElectricalconductivityofintrinsicsemiconductorsisdeterminedbytheconcentrationoffreeelectronsandholes1.4ExtrinsicMaterials:n-Typeandp-TypeMaterialsTheelectricalcharacteristicsofintrinsicsemiconductorsareimprovedbyaddingimpuritymaterialsinaprocesscalleddoping.

Thematerialscontainingimpurityatomsarecalledextrinsicsemiconductors,ordopedsemiconductors.Therearejusttwotypesofdopedsemiconductormaterials:n-type:impuritiesarefromgroupVelements,e.x.Phosphorusp-type:impuritiesarefromgroupIIIelements,e.x.Boron6N-typeSemiconductorsandCarriersAsemiconductorthatcontainsdonorimpurityatomsiscalledaN-typesemiconductor.Impuritiesinn-typematerialsactasDonorThemajoritycarriersinn-typematerialsareelectrons.Theminoritycarriersinn-typematerialsareholes.Phosphorusimpurityinn-typematerial.P-typeSemiconductorsandCarriersBoronimpurityinp-typematerial.AsemiconductorthatcontainsacceptorimpurityatomsiscalledaP-typesemiconductor.Impuritiesinp-typematerialsactasAcceptorThemajoritycarriersinp-typematerialsareholes.Theminoritycarriersinp-typematerialsare

electrons.n-typesemiconductorp-typesemiconductormajoritycarriers:electronsholesminoritycarriers:holeselectronsmass-actionlaw:ordopingn-typep-typeintrinsicsemiconductorextrinsicsemiconductor1.5

SemiconductorDiodeOneendofasiliconorgermaniumcrystalcanbedopedasap-typematerialandtheotherendasann-typematerial.Theresultisap-njunction.10Theresultistheformationofadepletionregionaroundthejunction.PNAnode(A)Cathode(K)DiodeOperatingConditionsAdiode(orp-njunction)hasthreeoperatingconditions:Nobias11ReversebiasForwardbiasExternalvoltageisappliedacrossthep-njunctionintheoppositepolarityofthep-andn-typematerials.DiodeOperatingConditions:

ReverseBiasReverseBiasThereversevoltagecausesthedepletionlayertowiden.Theelectronsinthen-typematerialareattractedtowardthepositiveterminal.Theholesinthep-typematerialareattractedtowardthenegativeterminal.12DiodeOperatingConditions:ForwardBiasForwardBiasExternalvoltageisappliedacrossthep-njunctioninthesamepolarityasthep-andn-typematerials.Theforwardvoltagecausesthedepletionlayertonarrow.Theelectronsandholesarepushedtowardthep-njunction.Theelectronsandholeshavesufficientenergytocrossthep-njunction.Theforwardbiasvoltagerequired:

silicondiode0.7V

germaniumdiode0.3VI-VCharacteristicsofSemiconductorDiodes14TheZenerregionisinthediode’sreverse-biasregion.Atsomepointthereversebiasvoltageissolargethediodebreaksdownandthereversecurrentincreasesdramatically.ZenerRegionTwomechanismsofelectricalbreakdownAvalanchebreakdownZener

breakdownThemaximumreverse-biasvoltagethatcanbeappliedbeforeenteringtheZenerregioniscalledthePeakInverseVoltage(PIV)orPeakReverseVoltage(PRV)TemperatureEffectsAstemperatureincreasesitaddsenergytothediode.Itreducestherequiredforwardbiasvoltageforforward-biasconduction.Itincreasestheamountofreversecurrentinthereverse-biascondition.Itincreasesmaximumreversebiasavalanchevoltage.Germaniumdiodesaremoresensitivetotemperaturevariationsthansilicondiodes.Semiconductordiodes(/pnjunction)actdifferentlytoDCandACcurrents.Therearethreetypesofresistances:

?

DC,orstatic,resistance

?

AC,ordynamic,resistance

?

AverageACresistance1.7ResistanceLevels17DC,orStatic,ResistanceForaspecificappliedDCvoltageVD,thediodehasaspecificcurrentID,andaspecificresistanceRD.Example1.2

AC,orDynamic,ResistanceExample1.3

TheacresistancedependsonDCoperatingpoint(ID)inthediode.rB

:bodyresistanceandcontactresistance.Itisverysmall(0.1

~2).InsomecasesrBcanbeignored.AC,orDynamic,ResistanceIntheforwardbiasregion:Inthereversebiasregion:Theresistanceisessentiallyinfinite.Thediodeactslikeanopen.1.8DiodeEquivalentCircuits21Therearethreeequivalentcircuitsforadiode:IdealEquivalentCircuitPiecewise-LinearEquivalentCircuitSimplified/ApproximateEquivalentCircuitIdeal

EquivalentCircuitOn-offSwitchConductioninonedirectionPiecewise-Linear

EquivalentCircuit23Simplified

EquivalentCircuitInreversebias,thedepletionlayerisverylarge.Thediode’sstrongpositiveandnegativepolaritiescreatetransition-ordepletion-regioncapacitance,CT.Theamountofcapacitancedependsonthereversevoltageapplied.

Inforwardbiasstoragecapacitanceor

diffusioncapacitance(CD)existsbesidesbarriercapacitanceasthediodevoltageincreases.1.9DiodeCapacitanceVF,forwardvoltageataspecificcurrentandtemperatureIF,maximumforwardcurrentataspecifictemperatureIR,maximumreversecurrentataspecifictemperaturePIVorPRVorV(BR),maximumreversevoltageataspecifictemperaturePowerdissipation,maximumpowerdissipatedataspecifictemperatureC,capacitancelevelsinreversebiastrr,reverserecoverytimeTemperatures,operatingandstoragetemperatureranges1.11DiodeSpecificationSheetsDataaboutadiodeispresenteduniformlyformanydifferentdiodes.Thismakescross-matchingofdiodesforreplacementordesigneasier.

25OtherTypesofDiodesZenerdiodeLight-emittingdiode(LED)PhotodiodeVaractordiodeAZenerisadiodeoperatedinreversebiasattheZenervoltage(VZ).CommonZenervoltagesarebeween1.8Vand200VImportantparametersforZenerDiodes:1.13ZenerDiodeSummaryofChapter1KeyItemsConstructionofap-njunctionCharacteristicsofasemiconductordiode(/p-njunction)-ElectricalconductioninonlyonedirectionDCresistanceandACresistanceEquivalentcircuitsforasemiconductordiodeChapter2:

DiodeApplications292.2Load-LineAnalysisTheloadlineplotsallpossiblecurrent(ID)conditionsforallvoltagesappliedtothediode(VD)inagivencircuit.E/RisthemaximumIDandEisthemaximumVD.WheretheloadlineandthecharacteristiccurveintersectistheQ-point,whichspecifiesaparticularIDandVDforagivencircuit.Load-lineanalysisCharacteristiccurveofthesolid-statedeviceLoadlineofthecircuit2.3EquivalentModelAnalysisConstantsasknownSiliconDiode:VD=0.7VGermaniumDiode:VD=0.3VAnalysisVD=0.7VVR=E–VDID=IR=IT=VR/RForwardBias:E>0.7ReverseBias:E<0.7DiodesideallybehaveasopencircuitsAnalysisVD=EVR=0VID=0AEquivalentModelAnalysis

Step1.Makeassumptions(‘short/forward’or‘open/reverse’)

Step2.Analysis/Checkassumptions

Step3.MakefinaldecisionExample2.4DetermineID,VD2,andVoStep1.MakeAssumptionsStep2.Analysis/CheckassumptionsStep3.Makefinaldecision2.5Half-WaveRectificationThediodeonlyconductswhenitisinforwardbias,thereforeonlyhalfoftheACcyclepassesthroughthediode.TheDCoutputvoltageis0.318Vm,whereVm=thepeakACvoltage.Note:Itisimportantthatthereversebreakdownvoltageratingofthediodebehighenoughtowithstandthepeakreverse-biasingACvoltage:Vm<PIV(orPRV)Usinganidealdiodeequivalent

UsingasimplifieddiodeequivalentExample2.82.6Full-WaveRectificationHalf-wave:Vdc=0.318Vm

Full-wave:Vdc=0.636VmTherectificationprocesscanbeimprovedbyusingmorediodesinafull-waverectifiercircuit.Full-waverectificationproducesagreaterDCoutput:Full-WaveRectificationBridgeRectifierFourdiodesarerequiredVDC=0.636Vm Full-WaveRectificationCenter-TappedTransformerRectifierRequiresTwodiodesCenter-tappedtransformerVDC=0.636(Vm)Example2.92.9ZenerDiodesTheZenerdiodeisoperatedinreversebiasattheZenerVoltage(Vz).WhenVi

VzTheZenerisonVoltageacrosstheZenerisVz

Zenercurrent:IZTheZenerPower:PZ=VZIZWhenVi<VzTheZenerisoffTheZeneractsasanopencircuitStep1.DeterminethestateoftheZenerdiodebyremovingitfromthenetworkandcalculatingthevoltageacrosstheresultingopencircuit.Step2.Substitutetheappropriateequivalentandsolveforthedesiredunknowns.Example2.17.FixedVi,FixedRLExample2.18.FixedVi,VariableRLExample2.19.VariableVi,FixedRLSummaryofChapter2AnalysismethodsofdiodecircuitsEquivalentModelLoad-LineAnalysisApplicationofDiodes

RectifierConversionsofACtoDCforDCoperatedcircuitsBatteryChargingCircuitsZenerDiodes:RegulatorOver

voltageProtectionSettingReferenceVoltages

Clipper/limiter:selfstudy

Clamper:selfstudy…Chapter3:

BipolarJunctionTransistors433.2TransistorConstructionTherearetwotypesoftransistors:pnp

npnTheterminalsarelabeled:E–EmitterB–BaseC–CollectorFeaturesofeachdopedregion:E–

HighlydopedB–

Verynarrow,lowestdopedC–

lowerdoped,largesurfaceTherearetwopnjunctions:Base-EmitterjunctionBase-Collectorjunctionpnpnpn3.3TransistorOperationTherefouroperationmodesdependingonthebiasconditionofeachpnjunction:Emitter-BasejunctionBase-CollectorjunctionActiveoperation(linearamplification)ForwardbiasReversebiasSaturationregionForwardbiasForwardbiasCutoffregionReversebiasReversebiasReverseoperationReversebiasForwardbiasTheactiveoperationregionisnormallyemployedforlinear(undistorted)amplifiers.CurrentsinaTransistorWiththeexternalsources,VEEandVCC,connectedasshownbelow:Theemitter-basejunctionisforwardbiasedThebase-collectorjunctionisreversebiasedThecollectorcurrentiscomprisedoftwocurrents:Emittercurrentisthesumofthecollectorandbasecurrents:PNPNPN3.4Common-BaseConfigurationCB:Thebaseiscommontobothinput(emitter–base)andoutput(collector–base)ofthetransistor.ThreebasicconfigurationsofaBJTaccordingtothecommonterminal:InputterminalCommonterminalOutputterminalCommon-Base(CB)EmitterBaseCollectorCommon-Emitter(CE)BaseEmitterCollectorCommon-Collector(CC)BaseCollectorEmitterCommon-BaseAmplifierInputCharacteristicsThiscurveshowstherelationshipbetweenofinputcurrent(IE)toinputvoltage(VBE)forvariouslevelsofoutputvoltage(VCB).Thisgraphdemonstratestheoutputcurrent(IC)

toanoutputvoltage(VCB)

forvariouslevelsofinputcurrent(IE).OutputCharacteristics

OperatingRegionsCutoffregion—Theamplifierisbasicallyoff.Thereisvoltage,butlittlecurrent.Saturationregion—Theamplifierisfullon.Thereiscurrent,butlittlevoltage.Activeregion—Operatingrangeoftheamplifier.Emitterandcollectorcurrents:Base-emittervoltage:Inactiveregion:ICBO=minoritycollectorcurrent.Thisisusuallysosmallthatitcanbeignored

Ideally:a=1Inreality:aisbetween0.9and0.998Alpha(a)Alpha()relatestheDCcurrentsICandIE:

Alpha()intheACmode:3.6Common–EmitterConfigurationCE:Theemitteriscommontobothinput(base-emitter)andoutput(collector-emitter).Theinputisonthebaseandtheoutputisonthecollector.Common-EmitterCharacteristicsBaseCharacteristicsInputCharacteristicsThiscurveshowstherelationshipbetweenofinputcurrent(IB)toinputvoltage(VBE)forvariouslevelsofoutputvoltage(VCE).CollectorCharacteristicsThisgraphdemonstratestheoutputcurrent(IC)

toanoutputvoltage(VCE)

forvariouslevelsofinputcurrent(IB).OutputCharacteristicsCommon-EmitterAmplifierCurrentsIdealCurrentsIE

=IC

+IB

IC

=IE

ActualCurrentsIC=IE+ICBOWhenIB=0Athetransistorisincutoff,butthereissomeminoritycurrentflowingcalledICEO.whereICBO=minoritycollectorcurrent.Thisisusuallysosmallthatitcanbeignored,exceptinhighpowertransistorsandinhightemperatureenvironments.Beta()InDCmode:InACmode:representstheamplificationfactorofatransistor.(issometimesreferredtoashfe,atermusedintransistormodelingcalculations)54DeterminingfromaGraphBeta()Note:AC

≈

DCRelationshipbetweenamplificationfactorsandBeta()RelationshipBetweenCurrents563.7Common–CollectorConfigurationCC:Thecollectoriscommontobothinput(base-collector)andoutput(emitter-collector).Theinputisonthebaseandtheoutputisontheemitter.Thecharacteristicsaresimilartothoseofthecommon-emitterconfiguration,excepttheverticalaxisisIE.VCEisatmaximumandICisatminimum(ICmin=ICEO)inthecutoffregion.ICisatmaximumandVCEisatminimum(VCEmin=VCEsat=VCEO)inthesaturationregion.Thetransistoroperatesintheactiveregionbetweensaturationandcutoff.3.8LimitationsofOperationCommon-emitter:CEConfigurationmore…3.9TransistorSpecificationSheetSummaryofChapter3

KeyInformationTransistorconstructionandoperationCurrentrelationship

ThreeBasicConfigurations:CECBCCCharacteristicsofCE,CBandCCconfigurationTransistorOperationRegionsActiveregionCutoffregionSaturationregion

ApplicationKeyNotesLimitsofOperationChapter4:

DCBiasing–BJTsBiasingBiasing

referstotheDCvoltagesappliedtoatransistorinordertoturnitonsothatitcanamplifytheACsignal.ToprovideenergyforamplificationToprovideaproperresponsetoaninputACsignalbydeterminingtheoperatingpointDCandACresponsearedifferent,soDCanalysiscanbetotallyseparatedfromtheacresponseThechoiceofparametersforDClevelswillaffecttheACresponse,andviceversaNonlinearDevices4.2OperatingPointTheDCinputestablishesanoperatingorquiescentpointcalledtheQ-point.

ActiveorLinearRegionOperationBase–EmitterjunctionisforwardbiasedBase–Collectorjunctionisreversebiased

CutoffRegionOperationBase–Emitterjunctionisreversebiased

SaturationRegionOperationBase–EmitterjunctionisforwardbiasedBase–CollectorjunctionisforwardbiasedBiasingandThreeStatesofOperationFixed-biascircuitEmitter-stabilizedbiascircuitVoltagedividerbiascircuitDCbiaswithvoltagefeedbackDCBiasingCircuits4.3FixedBiasCircuitSketchingtheDCequivalentisthefirststepforDCanalysis:Replacingthecapacitorwithanopen-circuitequivalent.Replacingtheinductorwithashort-circuitequivalent.DCsupplycanbeseparatedforanalysispurposeonlyMathematicalAnalysisFromKirchhoff’svoltagelaw:Solvingforthebasecurrent:+VCC–IBRB–VBE=0Base-emitterloopThecollectorcurrentisgivenby:FromKirchhoff’svoltagelaw:Collector-emitterloopTransistorSaturationWhenthetransistorisoperatinginthesaturationregion,itisconductingatmaximumcurrentflowthroughthetransistor.TransistorSaturationLevelLoadLineAnalysisICsatIC=VCC/RCVCE=0VVCEcutoffVCE=VCCIC=0mAwherethevalueofRBsetsthevalueofIBwhereIBandtheloadlineintersectthatsetsthevaluesofVCEandICTheQ-pointistheparticularoperatingpoint:Theendpointsoftheloadlineare:LoadequationbyKVL:CircuitValuesAffecttheQ-Pointmore…4.4Emitter-StabilzedBiasCircuitStability

referstoabiascircuitinwhichthecurrentsandvoltageswillremainfairlyconstantforawiderangeoftemperaturesandtransistorBeta()values.Addingaresistor(RE)totheemitterimprovesthestabilityofatransistor.ImprovedBiasedStability

MathematicalAnalysis

FromKirchhoff’svoltagelaw:SinceIE=(b+1)IB:SolvingforIB:FromKirchhoff’svoltagelaw:SinceIE

IC:Also:Collector-EmitterLoop

Base-EmitterLoop

Thecollectorcurrentisgivenby:TheroleofRE?

LoadlineAnalysis

VCEcutoff:

ICsat:Theendpointscanbedeterminedfromtheloadline.LoadequationbyKVL:4.5VoltageDividerBiasThisisaverystablebiascircuit.Thecurrentsandvoltagesarealmostindependentof

variationsin.ApproximateAnalysis

WhereIB<<I1andI2andI1

I2:WherebRE

>10R2:FromKirchhoff’svoltagelaw:4.6DCBiaswithVoltageFeedback

Anotherwaytoimprovethestabilityofabiascircuitistoaddafeedbackpathfromcollectortobase.InthisbiascircuittheQ-pointisonlyslightlydependentonthetransistorbeta,.Base-EmitterLoopFromKirchhoff’svoltagelaw:WhereIB<<IC:KnowingIC=IBandIE

IC,the

loopequationbecomes:SolvingforIB:ApplyingKirchoff’svoltagelaw:IERE+VCE+ICRC–VCC=0SinceIC

ICandIC=IB:IC(RC+RE)+VCE–VCC=0SolvingforVCE:VCE=VCC–IC(RC+RE)Base-EmitterLoopCollector-EmitterLoop4.8TransistorSwitchingNetworksTransistorswithonlytheDCsourceappliedcanbeusedaselectronicswitches.ICissensitiveto,temperature,VBE,andICO4.10BiasStabilizationSummaryofChapter4

Note:

Theanalysisforpnptransistorbiasingcircuitsisthesameasthatfornpntransistorcircuits.Theonlydifferenceisthatthecurrentsareflowingintheoppositedirection.DCanalysis:DCequivalentcircuitMathematicalanalysis(VBE=.7V)Load-lineanalysisTypicalDCbiasingcircuitsFixed-biascircuitEmitter-stabilizedbiascircuitVoltagedividerbiascircuitDCbiaswithvoltagefeedbackFactorsaffectingbiasstability79Chapter5:

BJTACAnalysis805.3BJTTransistorModelingAmodelisanequivalentcircuitthatrepresentstheACcharacteristicsofthetransistor.Amodelusescircuitelementsthatapproximatethebehaviorofthetransistor.TherearethreemodelscommonlyusedinsmallsignalACanalysisofatransistor:remodelHybridequivalentmodelHybrid∏modelACnetworkACequivalentcircuitSketchanACnetwork:RemoveDCsupplies(replacedbyshort)Thecouplingcapacitorandbypasscapacitorcanbereplacedbyashort815.4ThereTransistorModelBJTsarebasicallycurrent-controlleddevices,thereforetheremodelusesadiodeandacurrentsourcetoduplicatethebehaviorofthetransistor.OnedisadvantagetothismodelisitssensitivitytotheDClevel.Thismodelisdesignedforspecificcircuitconditions.82Common-BaseConfigurationInputimpedance:LowOutputimpedance:HighVoltagegain:voltageamplificationCurrentgain:NocurrentamplificationremodelforCBconfiguration83Common-EmitterConfigurationThedioderemodelcanbereplacedbytheresistorre.Usethecommon-emittermodelforthecommon-collectorconfiguration.remodelforCEconfigurationInputimpedance:higherthanCBOutputimpedance:lowerthanCBVoltagegain:Voltageamplification，VoandViare180°outofphaseCurrentgain:Currentamplificationremodelrequiresyoutodetermine,re,andro.845.5TheHybridEquivalentModelThefollowinghybridparametersaredevelopedandusedformodelingthetransistor.Theseparameterscanbefoundinaspecificationsheetforatransistor.hi=inputresistancehr=reversetransfervoltageratio(Vi/Vo)0

hf=forwardtransfercurrentratio(Io/Ii)ho=outputconductance

hi=inputresistancehr=reversetransfervoltageratio(Vi/Vo)0

hf=forwardtransfercurrentratio(Io/Ii)ho=outputconductance

SimplifiedGeneralH-ParameterModel:Approximatehybridequivalentmodel85re

Modelvs.h-ParameterModelCommon-EmitterCommon-Base865.6TheHybridpModelThehybridpmodelismostusefulforanalysisofhigh-frequencytransistorapplications.Atlowerfrequenciesthehybridpmodelcloselyapproximatethereparameters,andcanbereplacedbythem.87ACAnalysiswithEquivalentmodelsSection5.8CEwithfix-biasSection5.9CEwithvoltage-dividerbiasSection5.10CEwithemitterbiasSection5.14CEwithdccollectorfeedbackbiasSection5.13CEwithcollectorfeedbackSection5.11CC:EmitterfollowerSection5.12CBACequivalentcircuitwithremodelCalculate:ImpedanceInputimpedanceOutputimpedanceGainVoltagegainCurrentgainDCanalysistodeterminere

AmplificationcircuitACunknownsCE885.8Common-EmitterFixed-BiasConfigurationACnetworkACequivalentwithremodelTheinputisappliedtothebaseTheoutputisfromthecollectorHighinputimpedanceLowoutputimpedanceHighvoltageandcurrentgainPhaseshiftbetweeninputandoutputis18089Common-EmitterFixed-BiasCalculationsCurrentgainfromvoltagegain:Inputimpedance:Outputimpedance:Voltagegain:Currentgain:CEamplifiers:HighinputimpedanceLowoutputimpedanceHighvoltageandcurrentgainPhaseshiftbetweeninputandoutputis180905.9Common-EmitterVoltage-DividerBiasremodelrequiresyoutodetermine,re,andro.Inputimpedance:Outputimpedance:Voltagegain:Currentgainfromvoltagegain:Currentgain:915.10Common-EmitterEmitter-BiasConfiguration

(UnbypassedRE)Inputimpedance:Outputimpedance:Voltagegain:Currentgain:Currentgainfromvoltagegain:92Inputimpedance:Outputimpedance:Voltagegain:Currentgain:Thisisavariationofthecommon-emitterfixed-biasconfigurationInputisappliedtothebaseOutputistakenfromthecollectorThereisa180phaseshiftbetweeninputandoutput5.13Common-EmitterCollectorFeedbackConfiguration935.14CollectorDCFeedbackConfiguration945.11Emitter-FollowerConfiguration(CC)Emitter-followerisalsoknownasthecommon-collectorconfiguration.Theinputisappliedtothebaseandtheoutputistakenfromtheemitter.Thereisnophaseshiftbetweeninputandoutput.Inputimpedance:Outputimpedance:Voltagegain:Currentgain:Currentgainfromvoltagegain:955.12Common-BaseConfigurationTheinputisappliedtotheemitter.Theoutputistakenfromthecollector.Lowinputimpedance.Highoutputimpedance.Currentgainlessthanunity.Veryhighvoltagegain.Nophaseshiftbetweeninputandoutput.Inputimpedance:Outputimpedance:Voltagegain:Currentgain:965.17Two-PortSystemsApproachThisapproach:Reducesacircuittoatwo-portsystemProvidesa“Théveninlook”attheoutputterminalsMakesiteasiertodeterminetheeffectsofachangingloadWithVisetto0V:Thevoltageacrosstheopenterminalsis:whereAvNListheno-loadvoltagegain.

975.16EffectofLoadImpedanceonGainThismodelcanbeappliedtoanycurrent-orvoltage-controlledamplifier.Addingaloadreducesthegainoftheamplifier:985.16EffectofSourceImpedanceonGainThefractionofappliedsignalthatreachestheinputoftheamplifieris:Theinternalresistanceofthesignalsourcereducestheoverallgain:995.16CombinedEffectsofRSandRLonVoltageGainEffectsofRL:EffectsofRLandRS:1005.19CascadedSystemsTheoutputofoneamplifieristheinputtothenextamplifierTheoverallvoltagegainisdeterminedbytheproductofgainsoftheindividualstagesTheDCbiascircuitsareisolatedfromeachotherbythecouplingcapacitorsTheDCcalculationsareindependentofthecascadingTheACcalculationsforgainandimpedanceareinterdependentareloadedgains101R-CCoupledBJTAmplifiersInputimpedance,firststage:Outputimpedance,secondstage:Voltagegain:102CascodeConnection:CE–CBThisexampleisaCE–CBcombination.Thisarrangementprovideshighinputimpedancebutalowvoltagegain.ThelowvoltagegainoftheinputstagereducestheMillerinputcapacitance,makingthiscombinationsuitableforhigh-frequencyapplications.1035.20DarlingtonConnectionTheDarlingtoncircuitprovidesaveryhighcurrentgain—theproductoftheindividualcurrentgains:bD=b1b2Thepracticalsignificanceisthatthecircuitprovidesaveryhighinputimpedance.5.21FeedbackPairThisisatwo-transistorcircuitthatoperateslikeaDarlingtonpair,butitisnotaDarlingtonpair.Ithassimilarcharacteristics:HighcurrentgainLowVoltagegain(nearunity)LowoutputimpedanceHighinputimpedanceThedifferenceisthataDarlingtonusesapairofliketransistors,whereasthefeedback-pairconfigurationusescomplementarytransistors.bD=b1b2PNP1045.22CurrentMirrorCircuitsCurrentmirrorcircuitsprovideconstantcurrentinintegratedcircuits.Currentmirrorcircuitwithhigheroutputimpedance.1055.23CurrentSourceCircuitsConstant-currentsourcescanbebuiltusingFETs,BJTs,andcombinationsofthesedevices.IE

IC106SummaryofChapter5ACanalysisLoadlineanalysisMathematicalanalysisbysmallsignalmodelACanalysismethodbysmallsignalmodelDCanalysistodeterminereACequivalentcircuitbyremodelCalculationimpedanceandgainCEamplifierCBamplifierCCamplifierCascadedamplifiersystemEffectofRsandRLCE-CBChapter6:

Field-EffectTransistorsFETs(Field-EffectTransistors)aremuchlikeBJTs(BipolarJunctionTransistors).Similarities:?Amplifiers ?Switchingdevices ?ImpedancematchingcircuitsDifferences: