In an N-P-N transistor, P-type crystal is base

In P-N- P transistor operating as an amplifier with common emitter configurations a change in base current from 100 mA to 200 mA produces a change in collector current from 10 mA to 18 mA. The current gain of transistor is 80

A p- type semiconductor can be obtained by adding Ga to Si

To use a transistor as an amplifier the emitter- base junction is forward biased and the base ? collector junction is reverse biased