Question

The current gain of a transistor is $0.98$. If the transistor is used in a common emitter arrangement what would be the change in collector current corresponding to a change of $0.5mA$ in the base current.

• A. $24.5mA$
• B. $47.5mA$
• C. $32.5mA$
• D. $28.5mA$

Answer 1

Answer: (A)

Current gain of a transistor $=0.98$
Since it is less than $1$,
so it is the current gain in common base configuration
i.e., $\alpha =0.98$
So, current gain in common emitter configuration,
$\beta =\frac{\alpha }{1-\alpha }=\frac{0.98}{1-0.98}=\frac{0.98}{0.02}=49$
Now, $\beta =\frac{\Delta I_C}{\Delta I_B}$
where, $\Delta I_C=$ change in collector current $=?$
and $\Delta I_B=$ change in base current $=0.5mA$
On putting the values, we get
$49=\frac{\Delta I_C}{0.5mA}$
$\Rightarrow \Delta I_C=49\times 0.5mA=24.5mA$