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

AC power gain is the ratio of change in output power to the change in input power.AC power gain =Change in output powerChange in input power=∆Vc×∆ic∆Vi×∆ib=∆Vc∆Vi×∆ic∆ib=Av×βAC Where Av is voltge gain and (β)Ac is AC current gain. Also, Av/βAc =resistance gain =R0R1 Given, Av=50, R0=200 Ω, Ri=100 Ω Hence, 50/βAc=200100 βAc =25 Now, AC power gain = Av ×βAc  =50×25=1250