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ExamsGATETechnical

A standard CMOS inverter is designed with equal rise and fall times (βn = βp). If the width of the pMOS transistor in the inverter is increased, what would be the effect on the LOW noise margin (NML) and the HIGH noise margin NMH?

  1. NML increases and NMH decreases.
  2. NML decreases and NMH increases.
  3. Both NML and NMH increase.
  4. No change in the noise margins.

Correct answer: NML increases and NMH decreases.

Solution

Increasing the width of the pMOS transistor enhances its drive strength, which improves the ability to pull the output low, thus increasing the LOW noise margin (NML). However, this change can lead to a slower pull-up time compared to the pull-down time, resulting in a decrease in the HIGH noise margin (NMH).

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