quick NMOS question

[wakoko79]

suppose a you applied Vgs=+10V to a NMOS (in active/saturation Vgs)

basically its now a switch now right?

but what if I connect a negative voltage (say -24V) with a resistor (1k) to the drain?

will it still act as a closed switch?

basically I'm asking if it can conduct like a switch if the current (Ids) is going the other way (-Ids now).


thanks=)

 

[simonbramble]

quick NMOS answer: No. You have a body diode that opposes conventional current flow. You put a negative voltage on the drain (with respect to the source) and the body diode will conduct. The drain will sit at -0.6V. To get a true switch, you need back to back PCH FETs, like on page 1 of this datasheet:
https://cds.linear.com/docs/Datasheet/4365f.pdf

This will close off the channel going from left to right and right to left

Simon

 

[wakoko79]

It has been long, but thank you! =) +1