MOSFET

How does a MOSFET behave in the linear region, where the drain-source voltage VDS is sufficiently small?

  1. ALike a variable resistor whose resistance changes with gate voltage
  2. BLike a constant-current source independent of VDS
  3. CLike a diode that conducts in only one direction
Show answer and explanation

Answer: A. Like a variable resistor whose resistance changes with gate voltage

In the linear region, drain current is roughly proportional to VDS, and the proportionality constant (conductance) changes with gate voltage. In other words, the MOSFET behaves like a variable resistor controlled by the gate voltage. The on state of a MOSFET used as a switch is in this region. As VDS increases, it enters the saturation region where the current is nearly constant.

Practice this topic Back to topic

More MOSFET questions

  1. What is the purpose of the LDD (lightly doped drain) structure in a MOSFET?
  2. 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?
  3. What is the definition of the transconductance gm of a MOSFET?
  4. In a MOS structure on a p-type substrate, what is the state of the semiconductor surface when a negative voltage is applied to the gate?
  5. Which design makes the logic threshold of a CMOS inverter about half the supply voltage?