MOSFET

In an n-channel MOSFET, what happens to the threshold voltage when a negative voltage is applied to the substrate (body) relative to the source (body bias)?

  1. AIt rises
  2. BIt falls
  3. CIt does not change
Show answer and explanation

Answer: A. It rises

Reverse-biasing the source-substrate junction widens the depletion layer under the gate, and a larger gate voltage is needed to offset its charge. The threshold voltage therefore rises. This is called the body bias effect (body effect) and must be considered in circuit design.

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More MOSFET questions

  1. Which is a characteristic of a depletion-mode MOSFET?
  2. 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)?
  3. How does a MOSFET behave in the linear region, where the drain-source voltage VDS is sufficiently small?
  4. What is the purpose of the LDD (lightly doped drain) structure in a MOSFET?
  5. 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?