Question

A common emitter amplifier gives an output of $3 \,V$ for an input of $0.01 \,V$ . If $\beta$ of the transistor is $100$ and the input resistance is $1\text{ }k\Omega ,$ then the collector resistance is

• A. $\text{1 }k\Omega$
• B. $\text{3 }k\Omega$
• C. $\text{30 }k\Omega$
• D. $\text{10 }k\Omega$

Answer 1

Answer: (B)

$\text{3 }k\Omega$

Answer 2

In common emitter amplifier Voltage gain = current gain x 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 ${{R}_{o}}=\frac{30}{0.01}=3\,k\Omega$