What is amplification? With a circuit diagram, explain the working of npn transistor as an amplifier in CE configuration.

Explanation

Amplifier in CE mode: A small change in the base current produces a large change in the collector current. This is the principle behind amplification. In the circuit, the emitter-base junction is forward biased, the collector-base junction is reverse biased. The weak signal to be amplified is applied between E-B junction as shown. Either during the first half of second half of the input a.c. signal, the P.D. between emitter and base changes. As a result, the input current I also changes. Hence the output current changes by a large value.