The GATE Grind

GATE 2014 EC (EC4) – Question 21

Analog Circuits · BJT and MOSFET Amplifiers · 1 mark · Multiple choice

If the emitter resistance in a common-emitter voltage amplifier is not bypassed, it will ______.

  1. reduce both voltage gain and input impedance
  2. reduce voltage gain and increase input impedance
  3. increase voltage gain and reduce input impedance
  4. increase both voltage gain and input impedance

Practise this question in The GATE Grind →

Show answer and explanation

Correct answer: (B) reduce voltage gain and increase input impedance

Explanation

An unbypassed emitter resistor introduces emitter degeneration. The voltage gain magnitude decreases because the feedback reduces the changing base-emitter voltage; the base input resistance increases by approximately(β+1)RE. Therefore **voltage gain decreases and input impedance increases,B**.