Solid State Electronic Devices, 7th Edition

7.2 Amplification with BJTS

In this section we shall discuss rather simply the various factors involved in transistor amplification. Basically, the transistor is useful in amplifiers because the currents at the emitter and collector are controllable by the relatively small base current. The essential mechanisms are easy to understand if various secondary effects are neglected. We shall use total current (d-c plus a-c) in this discussion, with the understanding that the simple analysis applies only to d-c and to small-signal a-c at low frequencies. We can relate the terminal currents of the transistor i_E, i_B, and i_C by several important factors. In this introduction we shall neglect the saturation current at the collector (Fig. 7–3, component ...