Question

In a common-emitter transistor amplifier, the audio signal voltage across the collector is 3 $V$. The resistance of collector is 3 k$\Omega$. If the current gain is 100 and the base resistance is 2 k$\Omega$, the voltage and power gain of the amplifier is

• A. 200 and 1000
• B. 15 and 200
• C. 20 and 2000
• D. 150 and 15000

Answer 1

The correct option is D 150 and 15000

From collector current
$i_c=\frac{V}{R}=\frac{3}{3\times {10}^3}={10}^{-3}A$
and base current
$i_b=\frac{i_c}{\beta }=\frac{{10}^{-3}}{100}={10}^{-5}A$
As voltage

$V_{in}=i_b{R}_b$

$\therefore V_{in}={10}^{-5}\times 2\times {10}^3=2\times {10}^{-2}V$

Voltage gain
$A_v=\frac{V_{out}}{V_{in}}=\frac{3}{2\times {10}^{-2}}=150$

Power gain,
$=100\times 150=15000$