Answer to Question #162945 in Electric Circuits for berting

Question

In an NPN transistor, explain why most of the emitter

injected electrons pass through the base region and on to

the collector.

Answer 1

Answer

when the electrons travel from the negative terminal of the $V_{EE}$   supply voltage to the n-type emitter, these electrons are injected into the thin and lightly doped base region. Note that electrons are minority carriers in the p-type base region. So, only a few holes are available for recombination in the base. Thus only few of the electrons recombine with the holes doped into the base.

Secondly, the positive collector-base voltage $V_{cc}$  attracts the free electrons in the p-type thin and lightly doped base over to the collector side before they can recombine with holes in the base region.

Thus majority of emitter-injected electrons pass across the base region and into the collector region.