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FET Amplifiers MCQs

Practice FET Amplifiers MCQs with four options, answers and explanations for focused Electronics & Telecommunication Engineering revision.

Question 1
Electronic Devices & CircuitsFET Amplifiers

A source follower is the MOSFET counterpart of which BJT amplifier configuration?

  • ACommon collector
  • BCommon emitter
  • CCommon base
  • DDifferential pair only
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Correct Answer: A. Common collector
Explanation: The common-drain MOSFET stage, or source follower, provides non-inverting voltage buffering similar to a BJT emitter follower/common-collector stage.
Reference: Standard analog electronics: source follower
Question 2
Electronic Devices & CircuitsFET Amplifiers

A common-gate MOSFET amplifier is often useful at high frequencies partly because it?

  • AAvoids strong Miller multiplication of gate-drain capacitance at the input
  • BHas infinite voltage gain
  • CRequires no bias current anywhere
  • DAlways oscillates
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Correct Answer: A. Avoids strong Miller multiplication of gate-drain capacitance at the input
Explanation: With the gate at AC ground and input applied at the source, the common-gate topology largely avoids the Miller multiplication associated with common-source feedback capacitance.
Reference: Standard analog electronics: common-gate amplifier
Question 3
Electronic Devices & CircuitsFET Amplifiers

In a common-source MOSFET amplifier with a resistive drain load and no source degeneration, the output voltage is typically?

  • AApproximately 180 degrees out of phase with the input
  • BExactly in phase with the input
  • C90 degrees ahead at all frequencies
  • DIndependent of the input
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Correct Answer: A. Approximately 180 degrees out of phase with the input
Explanation: Increasing gate voltage raises drain current, increasing the drain-resistor drop and lowering drain voltage, so the stage is inverting.
Reference: Standard analog electronics: common-source amplifier
Question 4
Electronic Devices & CircuitsFET Amplifiers

Adding an unbypassed source resistor to a common-source MOSFET amplifier generally provides?

  • ALocal negative feedback and improved bias stability
  • BPositive feedback only
  • CInfinite input current
  • DRectification
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Correct Answer: A. Local negative feedback and improved bias stability
Explanation: If drain/source current rises, the source voltage rises, reducing VGS and opposing the increase. This source degeneration provides negative feedback.
Reference: Standard analog electronics: source degeneration