Question

The current gain in the common-emitter mode of a transistor is $10$. The input impedance is $ 20\,k\Omega $ and load of resistance is $ 100\,k\Omega $ . The power gain is

• A. 300
• B. 500
• C. 200
• D. 100

Answer 1

Answer: (B)

The power gain is defined as the ratio of charge in output power to the charge in input power.
Since, $P=V i$
Therefore,
Power gain = current gain $ \times $ voltage gain
$=\beta \times \beta\left(\frac{R_{\text {out }}}{R_{\text {in }}}\right)$
$ =\beta^{2}\left(\frac{R_{\text {out }}}{R_{\text {in }}}\right)$
Given, $\beta=10, R_{\text {in }}=20\, k \Omega$ and $R_{\text {out }}=100\, k \Omega$
$\therefore $ Power gain $=(10)^{2}\left(\frac{100}{20}\right) $
$=100 \times 5 $
$=500$