Question

A transistor is operated in common emitter configuration at constant collector voltage ${{V}_{C}}=1.5\,V$ such that a change in the base current from 100 $\mu A$ to 150 $\mu A$ produces a change in the collector current from 5 mA to 10 mA. The current gain ( $\beta$ ) is

• A. 67
• B. 75
• C. 100
• D. 50

Answer 1

Answer: (C)

100

Answer 2

AC current gain $\beta$ is defined as the ratio of the collector to the base current at constant collector voltage, $\beta =\left( \frac{\Delta {{i}_{C}}}{\Delta {{i}_{B}}} \right){{V}_{c}}$ Given $\Delta {{i}_{C}}=10\,mA-5mA=5mA$ $\Delta {{i}_{B}}=150\,\mu A-100\mu A=50\,\mu A$ $\therefore$ $\beta =\frac{5}{50\times {{10}^{-3}}}=100$