《双极晶体管》PPT课件

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1、Bipolartransistor§3-1IntroductionBipolarTransistorFirstbipolartransistor(BJT)wasinventedin1948Thetermbipolarcamefromthefactthatbothtypesofcarriers,i.e.,electronandholeplayimportantrolesinoperationFieldEffectTransistor(FET)isunipolar,inwhichonlyonetypeofcarrierisimportantBipolarTra

2、nsistorInVLSIera,BJTsstartstolosetheirshowstageduetotheemergenceofMOSFETs,whichpossessadvantageofsimplicityintermofprocessandcircuitdesignHowever,BJT’srefusetostepdownbecauseoftheirhighcurrentdrivecapabilityandsuperioranalogperformance(alsousefulinpowerapplications)Currenttrendist

3、ocombinethebestofMOSFETsandBipolardevices,whichisknownasBiCMOSprocessBJTdevicesarealsothepreferreddeviceforhighspeed(e.g.EmitterCoupleLogic.ECL)andRFapplicationsBipolarTransistorn+pnp+npBipolarTransistorThe”PlanarProcess”developedbyFairchildinthelate50sshapedthebasicstructureofthe

4、BJT,evenuptothepresentday.ModernBJTCloseenoughthatminoritycarriersinteract(negligiblerecombinationinbase)BJTbasicallyconsistsoftwoneighbouringpnjunctionsbacktoback:Forapartenoughthatdepletionregionsdon’tinteract(no“punchthrough”)UniquenessofBJT:highcurrentdrivabilityperinputcapaci

5、tancefastexcellentforanalogandfront-endcommunicationsapplications.BipolaroperationOperationdependsonthebiasconditionIBICIE§3-2CarrierdistributionCurrentFlowemittercurrentinjectedintothebasebasecurrentinjectedintotheemitterrecombinationinthebasecurrentregionreversebiasedcurrentacro

6、sstheBCJreversebiasedcurrentacrosstheBCJelectroncurrentfromtheemitterBipolarTransistorModesofoperationVCBSaturationForwardactiveCutoffInvertedactiveVEBPNPNPNSaturationForwardactiveCutoffInvertedactiveVBCVBEactiveinvertedsaturationcutoffforwardreverseforwardreverseforwardreverserev

7、erseforwardE-BC-BModeAnidealizedp-n-ptransistorinthermalequilibrium,thatis,whereallthereleadsareconnectedtogetherorallareground.Theimpuritydensitiesinthethreedopedregions,wheretheemitterismoreheavilydopedthanthecollector.Howeverthebasedopingislessthantheemitterdoping,butgreatertha

8、nthecollectordoping.TransistorAct