Question

In an NPN transistor circuit, the collector current is $10\text{mA}$. If $90\%$ of the electrons emitted reach the collector, the emitter current $\left(I_E\right)$ and base current $\left(I_B\right)$ respectively are

• A. $I_E=-1\text{mA},I_B=9\text{mA}$
• B. $I_E=9\text{mA},I_B=-1\text{mA}$
• C. $I_E=1\text{mA},I_B=11\text{mA}$
• D. $I_E=11\text{mA},I_B=1\text{mA}$

Answer 1

The correct option is D $I_E=11\text{mA},I_B=1\text{mA}$

Given $I_C=90$% of $I_E=0.9I_E$

$\Rightarrow I_E=\frac{I_C}{0.9}=\frac{10}{0.9}\approx 11\text{mA}$

Now, $I_E=I_B+I_C$

$\Rightarrow I_B=I_E-I_C=11-10=1\text{mA}$

Hence, $\left(D\right)$ is the correct answer.