Question

In common base circuit of a transistor, current amplification factor is $0.95$. Calculate the emitter current if base current is $0.2 \,mA$

• A. $2\,mA$
• B. $4\,mA$
• C. $6\,mA$
• D. $8\,mA$

Answer 1

Answer: (B)

Given, $\alpha=0.95, I_{b}=0.2 \,mA$
As $\,\,\, \alpha=\frac{I_{c}}{I_{e}}=\frac{I_{e}-I_{b}}{I_{e}}=1-\frac{I_{b}}{I_{e}}$
$\Rightarrow \,\,\,\,\frac{I_{b}}{I_{e}}=1-\alpha=1-0.95$
$\Rightarrow \,\,\,\, \frac{I_{b}}{I_{e}}=0.05 \Rightarrow \frac{0.2}{0.05} mA =I_{e}$
$\Rightarrow \,\,\,\, I_{e}=4 \,mA$