Question

The input resistance of a silicon transistor is $665 \,\Omega$. Its base current is changed by $15 \, \mu \,A$ which results in the change in collector current by $2 \,mA$. This transistor is used as a common emitter amplifier with a load resistance of $5\, k\,\Omega$. What is the voltage gain of the amplifier?

• A. 1002.5
• B. 1232.8
• C. 7235.9
• D. 9879.3

Answer 1

Answer: (A)

1002.5

Answer 2

$R_{i}=665 \Omega, \Delta I_{B}=15 \mu A =15 \times10^{-6} A$
$\Delta I_{C}=2 mA = 2 \times10^{-3} A ,R_{L}=5 k\Omega =5\times10^{3} \Omega$
$\beta=\frac{\Delta I_{C}}{\Delta I_{B}} =\frac{2\times10^{-3}}{15\times10^{-6}} =\frac{400}{3}$
Voltage gain, $A_{V }=\beta. \frac{R_{L}}{R_{i}}$
$A_{V}=\frac{400}{3}\times\frac{5\times10^{3}}{665}=1002.5$