Question

A transistor connected in common emitter configuration has input resistance $R_B=2k\Omega$ and load resistance of $5k\Omega$. If $\beta$ $=60$ and an input signal $12mV$ is applied, calculate the voltage gain, the power gain and the value of output voltage

• A. $A_v=150,V_{\text{out }}=1.8V$, and power gain $=9000$
• B. $A_v=20,V_{\text{out }}=1V$, and power gain $=2000$
• C. $A_v=150,V_{\text{out }}=1.5V$, and power gain $=8500$
• D. $A_v=20,V_{\text{out }}=1.5V$, and power gain $=2000$

Answer 1

Answer: (A)

Voltage gain
$A_v=\beta \frac{R_C}{R_B}=60\times \frac{5\times 10^3}{2\times 10^3}=150$
Power gain $={\beta }^2\frac{R_C}{R_B}=60\times 60\times 2.5=9000$
Base current $=I_B=\frac{12\times 10^{-3}}{2\times 10^3}=6\times 10^{-6}A$
$I_C=\beta I_B=60\times 6\times 10^{-6}=3.6\times 10^{-4}A$
Output $=I_C{R}_L=3.6\times 10^{-4}\times 5\times 10^3\Omega =1.8V$