Question

The current gain in the common emitter amplifier mode of a transistor is $10$ . The input impedance is $20k\Omega$ and load 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 change in output power and the change in input power.
Since, $P=VI$.
Therefore, Power gain = Current gain $X$
Voltage gain
$=\beta \times \beta \frac{R_{\text{out }}}{R_{\text{in }}}={\beta }^2\frac{R_{\text{out }}}{R_{\text{in }}}$
Given, $\beta =10,R_{\text{in }}=20k\Omega$ and $R_{\text{out }}=100k\Omega$.
Hence, Power gain $=10^2\frac{100}{20}=100\times 5=500$