Question

In npn transistor circuit, the collector current is $20\text{mA}$. If $80\text{\%}$ of the electrons emitted reach the collector, the emitter current will be

• A. $\text{10 mA}$
• B. $\text{15 mA}$
• C. $\text{25 mA}$
• D. $\text{20 mA}$

Answer 1

The correct option is C $\text{25 mA}$

Given:
Collector current, $I_C=20\text{mA}$
Since, $80\text{\%}$ of the electrons emitted reach to collector,

$\therefore 0.8I_E=I_C=20\text{mA}$,

Where, $I_E$ is the emitter current.

$\Rightarrow I_E=25\text{mA}$

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

$\begin{array}{c}\text{Why this question?}\\ \text{Concept: In n-p-n transistor, the holes}\\ \text{move from base (p-region) to emitter (n-region).}\end{array}$