Question

In a common emitter $(CE)$ amplifier having a voltage gain $G$, the transistor used has transconductance $0.03 \,mho$ and current gain $25$. If the above transistor is replaced with another one with transconductance $0.02$ $mho$ and current gain $20$, the voltage gain will be :

• A. $\frac{5}{4} G$
• B. $\frac{2}{3} G$
• C. $1.5 G$
• D. $\frac{1}{3} G$

Answer 1

Answer: (B)

$\frac{2}{3} G$

Answer 2

Voltage gain ${A_v = \frac{\Delta V_c}{\Delta V_B}} = \frac{R_L\Delta I_c}{\Delta V_B} = g_mR_L$ $\frac{A_{V1}}{A_{v2}} = \frac{g_{m1}}{g_{m2}}\Rightarrow \frac{G}{A_{v2}} = \frac{0.03}{0.02}\Rightarrow A_{v2} = \frac{2}{3}G$