Question

How does a MOSFET differ from a JFET?

• A. The type of charge carriers
• B. The presence of a gate oxide
• C. The use of bipolar junctions
• D. The reliance on majority carriers only

Hint:

MOSFETs have a key structural advantage — an insulating gate oxide — which allows for voltage control without current flow!

Answer 1

The Correct Option is B

The key difference between a MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor) and a JFET (Junction Field Effect Transistor) lies in the construction and operation of their gate terminals.
A MOSFET features a gate oxide layer (usually made of silicon dioxide) that electrically insulates the gate terminal from the channel. This allows the gate of a MOSFET to control the flow of current without direct contact with the channel, resulting in:

• High input impedance
• Very low gate current

In contrast, a JFET lacks a gate oxide; its gate is a reverse-biased p-n junction that controls the channel conductivity by varying the width of the depletion region. 

Why other options are incorrect:

• (A) Both MOSFETs and JFETs use majority carriers; the charge carrier type (electrons or holes) depends on the channel type (n-type or p-type).
• (C) Bipolar junctions are relevant to BJTs, not FETs.
• (D) Both devices primarily operate using majority carriers.