MOSFET

What is the advantage of a transmission gate, which connects an nMOS and a pMOS in parallel?

  1. AIt can pass both 0 and 1 without voltage loss
  2. BIt can amplify the signal current
  3. CIt can store data
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Answer: A. It can pass both 0 and 1 without voltage loss

An nMOS alone loses a threshold voltage when passing a 1 (high voltage), and a pMOS alone suffers a similar loss when passing a 0 (low voltage). Connecting both in parallel lets each compensate for the other, so both 0 and 1 are passed at full voltage. Transmission gates are used in multiplexers, latches and similar circuits.

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More MOSFET questions

  1. What failure can occur when a voltage far above the rating is applied between the gate and source of a MOSFET?
  2. What is the main reason the channel mobility of a MOSFET is lower than the mobility inside bulk silicon?
  3. In a short-channel MOSFET, what is the main reason the drain current falls below the (VGS − Vth) square law and approaches a linear dependence?
  4. Which expression roughly represents the delay of a CMOS logic gate? (C: load capacitance, V: supply voltage, I: drive current)
  5. What is the sign of the threshold voltage (relative to the source) of an enhancement-mode p-channel MOSFET?