Explanation

(b) The transistor has three regions, namely emitter, base and collector. The base is much thinner than the emitter, while collector is wider than both as shown in figure.
[image:14_image224.emf]
The emitter is heavily doped, so that it can inject a large number of charge carriers (electrons or holes) into the base. The base is lightly doped and very thin, it passes most of the emitter injected charge carriers to the collector. The collector is moderately doped.