The current gain in the common emitter mode of a transistor is 10. The input impedance is 20 kΩ and load of resistance is 100 kΩ. The power gain is:

500

The power gain is defined as the ratio of change in output power to the change in input power.

Since, P = VI

Therefore,

Power gain = current gain × voltage gain

$=β×β(\frac{R_{out}}{R_{in}})=β^2(\frac{R_{out}}{R_{in}})$

Here, $β = 10\,, R_{in}=20kΩ\,, R_{out}=100kΩ$

∴ Power gain = $(10)^2(\frac{100}{20})=100×50=500$