A common emitter amplifier has a voltage gain of 50, an input impedance of 100Ω and an output impedance of 200Ω. The power gain of the amplifier is

500 1000 1250 50

1250

Power gain = voltage gain × current gain $=V_G.I_G=\frac{V_0}{V_i}.\frac{I_0}{I_i}$ $=\frac{V_0^2}{V_i^2}.\frac{R_i}{R_0}=50×50×\frac{100}{200}=\frac{2500}{2}=1250$