Power Electronics and Motor Drive Systems

10.1. Power Bipolar Junction Transistor (BJT)

The power bipolar junction transistor (BJT) was the first semiconductor switch that was used for the implementation of power electronics switching topologies. There are two types of power transistors, the npn and the pnp, and are shown in Fig. 10.1(a) and (b), respectively. As shown in Fig. 10.1 the transistor is a three layer device and has three terminals: the base (B), the emitter (E), and the collector (C).

10.1.1. BJT Operation

Fig. 10.2 shows the construction prototype of an npn transistor which will be used to explain its operation. As can be seen, due to its construction, there are two depletion regions along its surface. The base p region is much smaller than the n region as shown in Fig. 10.2 ...