5.1.3 Small-Signal Models

Chapter 5.1.3 Small-Signal Models

Physics Lecture Notes – Phys 395 Electronics Book
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Physics Lecture Notes – Phys 395 Electronics Book

  • CHAPTER 5. TRANSISTOR CIRCUITS84ICVCEIB1IB2IB3constant ICnon−linear regionkneesIBVBEVPNFigure 5.4: Characteristic curves of an NPN transistor.the collector and emitter, whereas small changes in the collector-emitter voltage have littleeffect on the base. The result is that the base is always part of the input to a four-terminalnetwork. There are three common configurations: common emitter (CE), common collector(CC) and common base (CB), as shown in figure 5.5.Ec)b)a)BBCCEEBECCBFigure 5.5: Transistor basic circuit configurations: a) common emitter (CE), b) commoncollector (CC) and c) common base (CB).The operating characteristics of the different circuit configurations are shown in table 5.1.5.1.3Small-Signal ModelsA simple transistor model is given by IC = hFEIB. A more general model capable ofdescribing the family of characteristic curves is given byIC = IC(IB,VCE),(5.3)