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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:

  • Option 1) 5G/4


  • Option 2) 2G/3


  • Option 3) 1.5 G


  • Option 4) G/3



Answers (1)


As we learnt in

Amplifier -

Transistor is used as an amplifier

- wherein

in such circuit output is amplified as compared to input .




As  A_{V}=\beta \frac{R_{L}}{R_{i}}\:\:\:\: or\:\:\:\: G = \left( \frac{\beta}{R_{i}} \right )R_{L}

\Rightarrow G=g_{m}R_{L}

\Rightarrow G \propto g_{m}\left[ \because g_{m}= \frac{\Delta I_{C}}{\Delta I_{B}R_{1}} \right ]

\therefore \frac{G_{2}}{G_{1}}= \frac{gm_{2}}{gm_{1}}=\frac{0.02}{0.03}=\frac{2}{3}

\therefore voltage\:\: gain=\frac{2}{3}G

Correct option is 2.

Option 1)


This option is incorrect.

Option 2)


This option is correct.

Option 3)

1.5 G

This option is incorrect.

Option 4)


This option is incorrect.

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