Question

A common emitter amplifier circuit is built using $npn$ transistor, if $DC$ current gain is $250,R_{c}=$ $1K\Omega$ and $V_{CC}=10V$ . Calculate minimum base current for $V_{CE}$ to reach the saturation.

• A. $100μA$
• B. $7μA$
• C. $40μA$
• D. $10μA$

Answer 1

Answer: (C)

Using Ohm's law,
$i_{c}=\frac{10 V}{1 k \Omega}=10mA$
In common emitter configuration, current gain $\beta $
$\beta =\frac{i_{c}}{i_{b}}=250$
$\Rightarrow i_{b}=\frac{i_{c}}{\beta }=\frac{10 mA}{250}=40μA$