Chapter5_Differential and multistage amp.

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1、MicroelectronicCircuitsDifferentialandMultistageAmplifierOutlineIntroductionTheCMOSDifferentialPairSmall-SignalOperationoftheMOSDifferentialPairTheBJTDifferentialPairThedifferentialAmplifierwithActiveLoadMultistageAmplifiersSJTUEEDept.ZhouLingling2IntroductionTwor

2、easonsofthedifferentialamplifiersuitedforICfabricationICfabricationiscapableofprovidingmatcheddevices.Utilizingmorecomponentsthansingle-endedamplifierDifferentialcircuitsaremuchlesssensitivetonoiseandinterference.Differentialconfigurationenableustobiastheampli

3、fierandtocoupleamplifierstageswithouttheneedforbypassandcouplingcapacitors.SJTUEEDept.ZhouLingling3TheMOSDifferentialPair•Basicstructureofdifferentialpair.•CharacteristicsSJTUEEDept.ZhouLingling4TheMOSDifferentialPairSJTUEEDept.ZhouLingling5OperationwithaCommon-Mo

4、deInputVoltageSJTUEEDept.ZhouLingling6OperationwithaCommon–ModeInputVoltage•Symmetrycircuit.•Common-modevoltage.•CurrentIdividesequallybetweentwotransistors.•Thedifferencebetweentwodrainsiszero.•Thedifferentialpairrejectsthecommon-modeinputsignals.SJTUEEDept.ZhouL

5、ingling7OperationwithaDifferentialInputVoltageTheMOSdifferentialpairwithadifferentialinputsignalvapplied.idWithvpositive:v>idGS1v,i>i,andvGS2D1D2D1v;thus(v-v)willD2D2D1benegative.SJTUEEDe

6、pt.ZhouLingling8OperationwithaDifferentialInputVoltageDifferentialinputvoltage.Responsetothedifferentialinputsignal.ThecurrentIcanbesteeredfromonetransistortotheotherbyvaryingthedifferentialinputvoltageintherange:-2VOVvid2VOVWhendifferentialinputvoltageisverysma

7、ll,thedifferentialoutputvoltageisproportionaltoit,andthegainishigh.SJTUEEDept.ZhouLingling9Large-SignalOperationTransfercharacteristiccurvesNormalizedplotsofthecurrentsinaMOSFETdifferentialpair.NotethatVistheOVoverdrivevoltageatwhichQandQoperate12whenconducting

8、draincurrentsequaltoI/2.SJTUEEDept.ZhouLingling10Large-SignalOperationNonlinearcurves.Maximumvalueofinputdifferentialvoltage.Whenvid=0,twodraincurrentsa