So I have the P Channel MOSFET's Gate-Source voltage as 12-12 = 0V. This means the Drain and Source should be disconnected. However, I still see a 11.3V output from the drain. I have no idea what I am doing wrong. The threshold for the Vgs is -2V, and I am giving it 0V so it should be off. The DC power supplies are just 12V supplies.

My guess is that I should have a pull-down resistor from drain to the ground (around the LED and resistor) so that the drain pin is not floating when it is disconnected from the source. But, adding that resistor didn't solve the problem entirely.

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1 Answer 1


You've got the source and drain hooked up backwards. Notice that the body diode is forward biased and so it always be conducting. Swapping your drain and source connections should fix it.

  • \$\begingroup\$ Ahhh. I always thought the simulation places the part for you how it is normally used. So source on the top and drain on bottom. But I have a new problem I think. Now, I get a drain output of 0.859V. \$\endgroup\$ Jun 20, 2021 at 4:38
  • 1
    \$\begingroup\$ @AhmedAnwer The body diode has some reverse leakage. Try changing the MOSFET part# around (if your simulator lets you) to see how much that voltage changes with respect to the different part#'s. \$\endgroup\$
    – Ste Kulov
    Jun 20, 2021 at 4:55
  • \$\begingroup\$ got it. and this is stated as the current leakage on the datasheet right? as Igss? \$\endgroup\$ Jun 20, 2021 at 5:32

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