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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
$\frac{1}{3}G$
Detailed Solution
Voltage gain $A_V = \frac{\Delta V_C}{\Delta V_B} = \frac{R_L\Delta I_C}{\Delta V_B} = g_mR_L$
$\frac{A_{V_1}}{A_{V_2}} = \frac{g_{m_1}}{g_{m_2}} \Rightarrow \frac{G}{A_{V_2}} = \frac{0.03}{0.02}$
$A_{V_2} = \frac{2}{3}G$
$\frac{A_{V_1}}{A_{V_2}} = \frac{g_{m_1}}{g_{m_2}} \Rightarrow \frac{G}{A_{V_2}} = \frac{0.03}{0.02}$
$A_{V_2} = \frac{2}{3}G$