Question

explain how a CE amplifier amplifies the ac signal

Answer 1

The common emitter amplifier circuit consists of voltage divider biasing to provide the required base bias voltage. The voltage divider biasing has a potential divider so that the midpoint is used for supplying base bias voltage.

Resistor R1 is used for forawrd bias whereas R2 is used to maintain the bias. The coupling capacitor C1 seperates AC input signal and DC biasing signal. The resistor RE is for thermal stability and RL is the load resistance.

An increase in the resistor R2 increases the forward bias whereas increasing R1 decreases it. AC signal is applied at the base of the transistor causing small base current to flow. This results in the large collector current with the help of RL resistance. The voltage near the RL resistance changes because of its high value which is in the range of 5 to 10 kilo ohms. Therefore there exist huge amount of current in the collector in response to a small signal. Thus the CE transistor amplifies the ac signal.