Question

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

• A. $A _{ v }=150, V _{\text {out }}=1.8 V$, and power gain $=9000$
• B. $A _{ v }=20, V _{\text {out }}=1 V$, and power gain $=2000$
• C. $A _{ v }=150, V _{\text {out }}=1.5 V$, and power gain $=8500$
• D. $A_{ v }=20, V_{\text {out }}=1.5 V$, 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 $= I _{ C } R _{ L }=3.6 \times 10^{-4} \times 5 \times 10^3 \Omega=1.8 V$