Question

The value of $\alpha$ of a transistor is $0.9$. The change in the collector current corresponding to a change of $4mA$ in the base current in a common emitter arrangement is

• A. $36mA$
• B. $72mA$
• C. $18mA$
• D. $54mA$

Answer 1

The correct option is A $36mA$

Given that:
$\alpha =0.9$
$I_b=4mA$
For transistors,
$\beta =\frac{\alpha }{1-\alpha }$

$\beta =\frac{0.9}{1-0.9}=\frac{0.9}{0.1}=9$

Also,
$\beta =\frac{I_c}{I_b}$

$I_c=\beta I_b=\left(9\right)\left(4\right)=36mA$