Question

For enhancement MOSFET, the gate-source voltage must have

• A. Positive
• B. Negative
• C. Same polarity as the drain supply
• D. Opposite polarity as the drain supply

Hint:

Enhancement MOSFETs require an induced channel. Therefore the gate voltage must assist channel formation and hence has the same polarity as the drain supply.

Answer 1

The Correct Option is C

Concept: An enhancement MOSFET normally operates with no conducting channel at zero gate voltage. A gate voltage must be applied to induce the channel.

Step 1: Consider n-channel enhancement MOSFET.
For an n-channel MOSFET, \[ V_{GS}>0 \] is required. The drain supply is also positive. Hence gate and drain have the same polarity.

Step 2: Consider p-channel enhancement MOSFET.
For a p-channel MOSFET, \[ V_{GS}<0 \] and the drain supply is negative. Again the gate-source voltage has the same polarity as the drain supply.

Step 3: General conclusion.
Therefore, \[ \boxed{\text{Gate-source voltage has the same polarity as the drain supply}} \]