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 $0.5 \, mA$ in the base current.

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

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, $\quad \beta=\frac{\Delta I_{C}}{\Delta I_{B}}$
where, $\Delta I_{C}=$ change in collector current $=?$
and $\Delta I_{B}=$ change in base current $=0.5 \,mA$
On putting the values, we get
$49=\frac{\Delta I_{C}}{0.5 \,m A}$
$ \Rightarrow \Delta I_{C}=49 \times 0.5\, mA =24.5 \,mA$