Question

A transistor is used as a common emitter amplifier with a load resistance 2 K$\Omega$. the input resistance is 150 $\Omega$. Base current is changed by 20 $\mu$A which results in a change in collector current by $1.5mA$. The voltage gain of the amplifier is

• A. 900
• B. 1000
• C. 1100
• D. 1200

Answer 1

Answer: (B)

Given, load resistance $\left(R_e\right)=2k\Omega =2\times 10^3\Omega$
Input resistance $\left(R_i\right)=150\Omega$
Change in collector current $\left(\Delta I_C\right)=1.5mA$
$=1.5\times 10^{-3}A$
Change in base current $\left(\Delta I_B\right)=20\mu A=20\times 10^{-6}A$
We know that,
$\text{ voltage gain }=\frac{V_0}{V_i}=\frac{R_0\times \Delta I_C}{R_i\times \Delta I_B}$
$=\frac{2\times 10^3\times 1.5\times 10^{-3}}{150\times 20\times 10^{-6}}=\frac{3\times 10^6}{150\times 20}$
$=1000$