quick NMOS question

Status
Not open for further replies.

wakoko79

New Member
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=)
 
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
 
Status
Not open for further replies.
Cookies are required to use this site. You must accept them to continue using the site. Learn more…