Chapter4

Field-EffectTransistorAmplifiers4.1Field-EffectTransistors4.2FETAmplifiers第四章場(chǎng)效應(yīng)管放大電路4.1Field-EffectTransistors

Twotypes:junctionfield-effecttransistor(JFET)andthe metal-oxide-semiconductorFET(MOSFET)。4.1.1JunctionField-EffectTransistors(結(jié)型場(chǎng)效應(yīng)管)1.StructureandOperation(結(jié)構(gòu)及工作）1)BasicStructureandSymbol(基本結(jié)構(gòu)及符號(hào))

4.1場(chǎng)效應(yīng)管StructureofN-channelJFET(N溝道結(jié)型場(chǎng)效應(yīng)管結(jié)構(gòu))SymbolofN-channelJFET(N溝道結(jié)型場(chǎng)效應(yīng)管符號(hào))(c)

SymbolofP-channelJFET(P溝道結(jié)型場(chǎng)效應(yīng)管符號(hào))4.1場(chǎng)效應(yīng)管gateDepletionlayerdrainsource4.1場(chǎng)效應(yīng)管2．Characteristics(特性)1)TransferCharacteristic(轉(zhuǎn)移特性)TherelationbetweeniDanduGSforacertainuDS(在uDS一定時(shí),漏極電流iD與柵源電壓uGS之間的關(guān)系)。4.1場(chǎng)效應(yīng)管

TransferCharacteristicofN-channelJFETUP2)DrainCharacteristic(漏極輸出特性)ForUP≤uGS≤0,4.1場(chǎng)效應(yīng)管4.1.2Metal-oxide-semiconductorFETs(絕緣柵型場(chǎng)效應(yīng)管)

1.Enhancement-modeMOSFET(增強(qiáng)型絕緣柵場(chǎng)效應(yīng)管)1)StructureandSymbol(結(jié)構(gòu)及符號(hào))4.1場(chǎng)效應(yīng)管StructureofN-channelenhancement-modeMOSFETSymbolofN-channelenhancement-modeMOSFETSymbolofP-channelenhancement-modeMOSFET2)Characteristics(特性)（1）TransferCharacteristicofN-channelEnchancement-modeMOSFETwhenuGS≥UT,（2）DrainCharacteristicofN-channelEnchancement-modeMOSFET4.1場(chǎng)效應(yīng)管（a）TransferCharacteristic（b）DrainCharacteristic4.1場(chǎng)效應(yīng)管UT

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

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