Why is the base of a transistor made thin and is lightly doped? - Vidyadip

Question

Why is the base of a transistor made thin and is lightly doped?

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Answer

The base of a transistor is lightly doped than the emitter and is made narrow so that virtually all the electrons injected from the emitter (in an npn tran-sistor) diffuse right across the base to the collector junction without recombining with holes. That is, the base width is kept less than the recombination distance. Also, the emitter is much heavily doped than the base to improve emitter efficiency and common-base current gain a.

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