Question

An npn transistor operates as a common emitter amplifier, with a power gain of $60dB$. The input circuit resistance is $100\Omega$ and the output load resistance is $10k\Omega$. The common emitter current gain $\beta$ is :

• A. $60$
• B. ${10}^4$
• C. $6\times {10}^2$
• D. ${10}^2$

Answer 1

The correct option is D ${10}^2$

$A_v\times \beta =P_{gain}$
$60=10lo{g}_{10}\left(\frac{P}{P_0}\right)$
$P={10}^6={\beta }^2\times \frac{R_{out}}{R_{in}}$
${10}^6={\beta }^2\times \frac{{10}^4}{100}$
${\beta }^2={10}^4$
$\beta =100$