MOSFET

In a CMOS inverter, what is the current that flows from the supply to ground while the input is switching called?

  1. AGate leakage current
  2. BShort-circuit (crowbar) current
  3. CSubthreshold current
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Answer: B. Short-circuit (crowbar) current

While the input passes through intermediate voltages, the nMOS and pMOS are both slightly on at the same time, and current flows directly from the supply to ground. This is the short-circuit (crowbar) current. It grows when input rise and fall times are slow, so fast signal transitions are important.

  • A. Gate leakage current is current through the gate insulator.
  • B. Correct. It flows while both transistors are on at the same time.
  • C. Subthreshold current is leakage in a transistor that is off.
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