Question

The current gain in the common emitter amplifier mode of a transistor is $10$ . The input impedance is $20 \, k\Omega $ and load 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 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, $\beta=10, R_{\text {in }}=20 \,k \Omega$ and $R _{\text {out }}=100 \,k \Omega$.
Hence, Power gain $=10^{2} \frac{100}{20}=100 \times 5= 500$