CBSE Class 12-science Answered
The power gain or power amplification (Ap) is the product of the current gain βac and the voltage gain Av:
Ap = βac x Av
Here βac = ΔIC/ΔIB = (1 x 10-3)/(10 x 10-6) = 100 and
Av = -βac x RL/RiWhere RL is the load resistance and Ri is the input resistance. The negative sign just indicates that in the common emitter configuration the output signal is phase shifted by 180o.
[We use the load resistance RL instead of the output resistance Ro(of the amplifier stage) in the above expression since the load resistance is small compared to the transistor output resistance. (The output resistance of the amplifier stage is the parallel combined value of RL and the transistor output resistance)].
Ignoring the negative sign, Av = 100 x 5/1 = 500
Therefore, power gain Ap = βac x Av = 100 x 500 = 5000.