Question

The input resistance of a silicon transistor is $100$ $\Omega$. Base current is changed by $40\mu A$ which results in a change in collector current by $2mA$. This transistor is used as a common emitter amplifier with a load resistance of $4K$ $\Omega$. The voltage gain of the amplifier is:

• A. $3000$
• B. $4000$
• C. $1000$
• D. $2000$

Answer 1

The correct option is D $2000$

For a common emitter amplifier,
Current gain $\left(\beta \right)=\frac{\Delta I_C}{\Delta I_B}=\frac{2\times {10}^{-3}}{40\times {10}^{-6}}$
$\beta =50$
Voltage gain$=\beta \left(\frac{R_{out}}{R_{in}}\right)$
$=50\left(\frac{4\times {10}^3}{100}\right)$

$=2000$