Question

Difference between three segments of a transistor on the basis of their size and level of doping. With the help of necessary circuit diagram, describe briefly how $n-p-n$ transistor in $CE$ mode as switch works.

Answer 1

Emitter (E) - Emitter is heavily doped and is the left hand

side thick layer of the transistor.

Base (B) - It is the central thin layer of the transistor,

which is lightly doped.

Collector (C) - It is the right hand side thick layer of the transistor,

which is moderately doped.

n - p - n Transistor as an amplifier:

The input circuit is forward biased by a low voltage battery. Hence,

the resistance of the input | circuit is small.

The output circuit is reverses biased using a high voltage battery.

Hence, the resistance of the output is large.