For a common base configuration of npn transistor, collector current is greater than base current. Why?

In a common base configuration of an NPN transistor, the collector current is greater than the base current due to the transistor's operation principle. Here's a step-by-step explanation:

1. The NPN transistor consists of two n-type semiconductors (the emitter and the collector) separated by a p-type semiconductor (the base).

2. When a small current is applied to the base-emitter junction, it causes the junction to become forward-biased, allowing a large number of electrons to move from the emitter to the base.

3. However, the base is thin and lightly doped, which means it can't hold many charge carriers (electrons). As a result, most of the electrons (about 95-99%) pass through the base and reach the collector.

4. The remaining electrons (about 1-5%) combine with holes in the base, constituting the base current (Ib).

5. Therefore, the collector current (Ic) is the sum of the base current (Ib) and the current of the electrons that passed through the base to the collector. This is why the collector current is greater than the base current in a common base configuration of an NPN transistor.

6. Mathematically, this is represented as Ic = Ib + Ie, where Ie is the emitter current. Since Ie is much larger than Ib, Ic is also much larger than Ib.