Question

The _____________ of a MOSFET is affected by the voltage which is applied to the back contact.

(a) Threshold Voltage

(b) Output Voltage

(c) Both threshold and output voltage

(d) Neither of the threshold nor the output voltage

I got this question during an interview.

This intriguing question comes from The Body Effect topic in chapter MOS Field Effect Transistors (MOSFETs) of Electronic Devices & Circuits

Answer 1

Correct answer is (a) Threshold Voltage

Explanation: The voltage difference between the source and the bulk, VBS changes the width of the depletion layer and therefore also the voltage across the oxide due to the change of the charge in the depletion region. This results in a difference in threshold voltage which equals the difference in charge in the depletion region divided by the oxide capacitance.