Solid State Electronic Devices, 7th Edition

7.5 Generalized Biasing

The expressions derived in Section 7.4 describe the terminal currents of the transistor, if the device geometry and other factors are consistent with the assumptions. Real transistors may deviate from these approximations, as we shall see in Section 7.7. The collector and emitter junctions may differ in area, saturation current, and other parameters, so that the proper description of the terminal currents may be more complicated than Eqs. (7–18) and (7–19) suggest. For example, if the roles of the emitter and collector are reversed, these equations predict that the behavior of the transistor is symmetrical. Real transistors, on the other hand, are generally not symmetrical between emitter and collector. This is a particularly ...