Question

The current gain in the common-emitter mode of a transistor is $10$. The input impedance is $20k\Omega$ and load of resistance is $100k\Omega$ . 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, $P=Vi$
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, $\beta =10,R_{\text{in }}=20k\Omega$ and $R_{\text{out }}=100k\Omega$
$\therefore$ Power gain $=(10{)}^2\left(\frac{100}{20}\right)$
$=100\times 5$
$=500$