MOSFET

Which is a characteristic of a depletion-mode MOSFET?

  1. AIt has no gate
  2. BA channel exists even at a gate voltage of 0 V, so current flows
  3. CNo current flows even when the gate voltage is above the threshold voltage
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Answer: B. A channel exists even at a gate voltage of 0 V, so current flows

A depletion-mode MOSFET has a channel built in, so current flows even at a gate voltage of 0 V (normally on). Applying gate voltage of the opposite polarity removes the channel and stops the current. A MOSFET that does not conduct at 0 V gate voltage (normally off) is called enhancement mode.

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More MOSFET questions

  1. Which value is closest to the theoretical lower limit of a MOSFET's subthreshold swing at room temperature (the gate voltage needed to change the drain current by one decade below threshold)?
  2. How does a MOSFET behave in the linear region, where the drain-source voltage VDS is sufficiently small?
  3. What is the purpose of the LDD (lightly doped drain) structure in a MOSFET?
  4. In a MOSFET in saturation, what is the phenomenon in which raising the drain voltage shortens the effective channel length and slightly increases the drain current?
  5. What is the definition of the transconductance gm of a MOSFET?