Question

If an emitter current is changed by 4 mA, the collector current changes by 3.5 mA. The value of β will be :

• A. 7
• B. 0.875
• C. 0.5
• D. 3.5

Hint:

$\alpha$ is always less than 1 (common base gain), while $\beta$ is usually much larger than 1 (common emitter gain).

Answer 1

The Correct Option is A

Step 1: Given $\Delta I_E = 4$ mA and $\Delta I_C = 3.5$ mA.
Step 2: Current gain $\alpha = \frac{\Delta I_C}{\Delta I_E} = \frac{3.5}{4} = 0.875$.
Step 3: Relation: $\beta = \frac{\alpha}{1 - \alpha} = \frac{0.875}{1 - 0.875} = \frac{0.875}{0.125}$.
Step 4: $\beta = 7$.