Q. A common emitter amplifier given an output of 3 V for an input of 0.01 V. If $\beta$ of the transistor is 100 and the input resistance is 1 k$\Omega$, then the collector resistance is
A) 1 k$\Omega$
B) 3 k$\Omega$
C) 30 k$\Omega$
D) 30 $\Omega$
Explanation
(b) In common emitter amplifier
Voltage gain = current gain $\times$ resistance gain
Or $A_{V} = \beta \times \frac{R_{o}}{R_{i}}$
Or $\frac{V_{o}}{V_{i}} = \beta\ \frac{R_{o}}{R_{i}}$
Or $\frac{3}{0.01} = 100 \times \frac{R_{o}}{1 \times 10^{3}}$
Or $R_{o} = \frac{3}{0.01} =$3 k$\Omega$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.