Question

In common emitter amplifier, the current gain is $20.$ The collector resistance and input resistance are $4k\Omega$ and $800\Omega$ respectively. If the input voltage is $0.01\text{V}.$ The output voltage is

• A. $0.01\text{V}$
• B. $1\text{V}$
• C. $100\text{V}$
• D. $200\text{V}$

Answer 1

The correct option is B $1\text{V}$

Given,

$\text{Current gain,}\beta =20\text{Collector resistance (output),}{R}_0=4k\Omega =5\times {10}^3\Omega \text{Input resistance,}{R}_i=800\Omega \text{Input voltage,}{V}_i=0.01\text{V}$

$\because$ The voltage gain,

$A_v=\beta \times \frac{R_0}{R_i}=20\times \frac{4\times {10}^3}{800}=100$

Also, $A_v=\frac{V_0}{V_i}$

$\Rightarrow V_0=A_v\times V_i=100\times 0.01=1\text{V}$

<!--td {border: 1px solid #ccc;}br {mso-data-placement:same-cell;}--> Hence, $\left(B\right)$ is the correct answer.