场效应管放大电路17461课件

Chapter4

Field-EffectTransistorAmplifiers4.1Field-EffectTransistors4.2FETAmplifiers第四章场效应管放大电路4.1Field-EffectTransistors

Twotypes:junctionfield-effecttransistor(JFET)andthe metal-oxide-semiconductorFET(MOSFET)。4.1.1JunctionField-EffectTransistors(结型场效应管)1.StructureandOperation(结构及工作）1)BasicStructureandSymbol(基本结构及符号)

4.1场效应管StructureofN-channelJFET(N沟道结型场效应管结构)SymbolofN-channelJFET(N沟道结型场效应管符号)(c)

SymbolofP-channelJFET(P沟道结型场效应管符号)4.1场效应管gateDepletionlayerdrainsource4.1场效应管2．Characteristics(特性)1)TransferCharacteristic(转移特性)TherelationbetweeniDanduGSforacertainuDS(在uDS一定时,漏极电流iD与栅源电压uGS之间的关系)。4.1场效应管

TransferCharacteristicofN-channelJFETUP2)DrainCharacteristic(漏极输出特性)ForUP≤uGS≤0,4.1场效应管4.1.2Metal-oxide-semiconductorFETs(绝缘栅型场效应管)

1.Enhancement-modeMOSFET(增强型绝缘栅场效应管)1)StructureandSymbol(结构及符号)4.1场效应管StructureofN-channelenhancement-modeMOSFETSymbolofN-channelenhancement-modeMOSFETSymbolofP-channelenhancement-modeMOSFET2)Characteristics(特性)（1）TransferCharacteristicofN-channelEnchancement-modeMOSFETwhenuGS≥UT,（2）DrainCharacteristicofN-channelEnchancement-modeMOSFET4.1场效应管（a）TransferCharacteristic（b）DrainCharacteristic4.1场效应管UT

N-channeldepletion-modeMOSFET（a）Transfercharacteristic（b）DraincharacteristicWhenuGS≥UP,4.1场效应管Up4.2FETAmplifiersThecommon-sourceamplifierThecommon-drainamplifierThecommon-gateamplifier4.2场效应管放大器Thecommon-sourceJFETamplifierSmall-signalJFETparametersDefinetransconductanceas:4.2场效应管放大器Small-signalmodelofJFET4.2场效应管放大器Acommon-sourceJFETamplifierwithfixedbias4.2场效应管放大器Thesmall-signalequivalentcircuit4.2场效应管放大器Solution:4.2场效应管放大器Bias-stabilizedJFETamplifiers4.2场效应管放大器Self-biasedJFETamplifier4.2场效应管放大器Unbypassedsourceresistor4.2场效应管放大器Common-drainamplifier4.2场效应管放大器Example

TheJFETinthecircuithasgm=5×10-3Sandrd=100k.Find1.theinputresistance;2.thevoltagegain.4.2场效应管放大器Common-gateamplifier4.2场效应管放大器Small-signalMOSFETamplifiersFordepletion-typeMOSFET,theparameterofsmall-signalmodelisidenticaltotheparameterofJFETsmall-signalmodel.Forenhancement-typeMOSFET:4.2场效应管放大器Acommon-sourceNMOSamplifier4.2场效应管放大器ExampleTheMOSFETshowninthecircuithasthefollowingparameters:VT=2V,ß=0.5×10-3,rd=75k.ItisbiasedatID=1.93mA.1.Findtheinputresista