What is meant by the MOSFET is pinched-off? It is same as in the JFET case where the depletion region becomes too large until the electron cannot flow through the transistor?

  • 1
    \$\begingroup\$ Not a duplicate but extremely related: Why MOSFET Pinchoff occurs \$\endgroup\$
    – user103380
    Commented Jun 1, 2020 at 18:06

1 Answer 1


When a positive gate-source voltage in NMOS is applied, As voltage increases once the voltage reaches the threshold voltage, the channel will be created and the device is ready to conduct electron or holes (in case of PMOS) through the channel between drain and source.

So by applying drain-source voltage it maximizes at the drain end and minimum at the source end. As Drain-source voltage is increased, it attracts the electrons from source end to drain end and current flows from Drain to Source, in this case, we're in the triode region.

As the Vds increases, we reach a point where Vds=Vgs-Vth that is pinch-off, at which the current becomes saturated and almost constant current flows. enter image description here

As Vds increases, the channel becomes smaller till it's OFF, but in a real case, the channel is not completely pinched-off, in fact, it is more like pressing a pipe end with your fingers. There is a uniform electric field at the pinched end hence instead of stopping the current there is a constant saturated current.

reference: https://www.quora.com/What-is-pinch-off-effect-of-MOSFET

  • \$\begingroup\$ Hi, As required by this site rule, when you include something in an answer (e.g. photo, image or text) which isn't your own original work, you need to properly reference (cite) it. That image seems to have come from somewhere else, so in order to comply with that rule, can you edit your answer and add a link back to the original source web page, please? Thanks :-) \$\endgroup\$
    – SamGibson
    Commented Jun 2, 2020 at 10:01
  • \$\begingroup\$ Thanks for the notice, I added the reference. \$\endgroup\$ Commented Jun 2, 2020 at 16:18
  • \$\begingroup\$ The "reference" link doesn't actually seem to have the image in question. \$\endgroup\$
    – Hearth
    Commented Jun 2, 2020 at 16:57
  • \$\begingroup\$ It has the image in the answer, isn't that count? \$\endgroup\$ Commented Jun 3, 2020 at 5:59

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