Question

The current gain of transistor in a common base circuit is 40. The ratio of emitter current to base current is

• A. 40
• B. 41
• C. 42
• D. 43

Answer 1

Answer: (B)

41

Given that: $\beta =40$
Hence, $\alpha =\frac{\beta }{1+\beta }$
$\alpha =\frac{40}{1+40}$

$\alpha =\frac{40}{41}$

Now, $\beta =\frac{I_c}{I_b}$ and $\alpha =\frac{I_c}{I_e}$

$\Rightarrow I_c=\beta I_b=\alpha I_e$

$\Rightarrow \frac{I_e}{I_b}=\frac{\beta }{\alpha }$

$\therefore \frac{I_e}{I_b}=\frac{40}{\frac{40}{41}}=41$