Question

In case of bipolar transistor $\beta =45$. The potential drop across the collector resistance of $1k\Omega$ is $5V$. The base current is approximately

• A. $222\mu A$
• B. $55\mu A$
• C. $111\mu A$
• D. $45\mu A$

Answer 1

The correct option is C $111\mu A$

From Ohm's law, the current in the collector resistance is $\frac{5V}{1k\Omega }=5mA$

This is the collector current $I_C$.

Now current gain $\beta$ is the ratio of collector current to base current.

$⟹\beta =\frac{I_C}{I_B}$

$⟹I_B=\frac{I_C}{\beta }$

$=\frac{5mA}{45}$

$=111\mu A$