Question

If a change of $8.0mA$ in the emitter current brings a change of $7.9mA$ in the collector current, the values of $\alpha$ and $\beta$ are

• A. $0.99,90$
• B. $0.96,79$
• C. $0.97,99$
• D. $0.99,79$

Answer 1

The correct option is D $0.99,79$

Given that, change in emitter current, $\Delta I_E=8mA$
and change in collector current, $\Delta I_C=7.9mA$
We know that,
$\alpha =\frac{\Delta I_C}{\Delta I_E}\Rightarrow \alpha =\frac{7.9}{8}\Rightarrow \alpha \simeq 0.99$
Also we know that
$\beta =\frac{\alpha }{1-\alpha }$
$\Rightarrow \beta =\frac{\frac{7.9}{8}}{1-\frac{7.9}{8}}=\frac{7.9}{8-7.9}$
or $\beta =\frac{7.9}{0.1}=79$
Hence, the required answer is $\alpha =0.99$ and $\beta =79$