The GATE Grind

GATE 2016 EC – Question 22

Electronic Devices · P-N Junction and Semiconductor Devices · 1 mark · Multiple choice

Consider the following statements for a metal oxide semiconductor field effect transistor (MOSFET):

P: As channel length reduces, OFF-state current increases.

Q: As channel length reduces, output resistance increases.

R: As channel length reduces, threshold voltage remains constant.

S: As channel length reduces, ON current increases.

Which of the above statements are INCORRECT?

  1. P and Q
  2. P and S
  3. Q and R
  4. R and S

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Show answer and explanation

Correct answer: (C) Q and R

Explanation

In short-channel devices the OFF current rises (P is true) and the ON current rises (S is true). The output resistance falls, because channel length modulation gets stronger, so Q is false. The threshold voltage also drops as the channel gets shorter (roll-off), so R is false. The incorrect statements are Q and R.