Question

A transistor is used in a common-emitter mode in an amplifier circuit. When a single input voltage of $20\text{mV}$ is added to the base emitter voltage, the base current changes by $20\mu A$ and the collector current changes by $2mA$. The load resistor is $5k\Omega$. What is the value of current gain $\left(\beta \right)$?

• A. $10$
• B. $10$
• C. $100$
• D. ${10}^6$

Answer 1

The correct option is C $100$

Given,
$\Delta I_B=20\times {10}^{-6}A\Delta I_C=2\times {10}^{-3}A$
$\beta =?$
This system work as a Common Emitter Connection (CE-configuration)

for CE-configuration $\beta =\frac{\Delta I_C}{\Delta I_B}=\frac{2\times {10}^{-3}}{20\times {10}^{-6}}=100$
Hence, $\beta =100$