If the emitter resistance in a common-emitter voltage amplifier i
A. reduce both the voltage gain and the input impedance
B. reduce the voltage gain and increase the input impedance
C. increase the voltage gain and reduce the input impedance
D. increase both the voltage gain and the input impedance
Please scroll down to see the correct answer and solution guide.
Right Answer is: B
SOLUTION
The circuit diagram of a Common-emitter amplifier without a bypass is drawn as:
Voltage gain is given by:
\(\frac{{{V_0}}}{{{V_i}}} = \frac{{ - {g_m}{R_i}'}}{{1 + {g_m}{R_E}}}\)
Where RL’ = RL’||RE
And the circuit diagram of a common emitter amplifier with bypass is drawn as:
Voltage gain is given by:
\(\frac{{{V_o}}}{{{V_i}}} = - {g_m}{R_i}'\)
Where, RL’ = RC||RL
Input resistance, Ri = rx
Observation: Clearly, the voltage gain decreases, and the input resistance is increased if the emitter is not bypassed.
