Circuit Operation of Common Emitter (CE) Amplifier

When the positive half-cycle of signal is provided

(1)             As the base of transistor is already positive relating to biasing, so voltage (VBC) increases.

(2)             Due to increase in VBE , the forward bias of Emitter-base junction also increases.

(3)             IB is also slightly increased.

(4)             As a result of increase in IB (Base Current), the IC (Collector Current) increase up to B times as (IC = BIB).

(5)             Due to increase of IB , a large increase in ICRC drop occurs.

(6)             VCE decreases according to following equation.

VCE = VCCICRC

Thus, negative half-cycle of input is achieved. It means that when positive input signal is provided to such circuit, then the amplified output signal is negative, (as shown in figure)

When negative half-cycle is provided to input then the achieved output cycle is positive.