what happens if I exceed the maximum rating of the drain-to-source voltage of an N-MOSFET
I am using NTNS3C94NZ so 12 V in this case
datasheet:
https://www.onsemi.com/pub/Collateral/NTNS3C94NZ-D.PDF
does it act as a zener? as a short?
is it destructive?
what voltage/current can it handle?
I did the test with 20 V, it seems that the over-voltage on the drain leaks to the gate, enables the transistor, that start conducting and pulls the drain low.
so externally, it did act as a ~14 V Zener Drain-to-Source with 20 mA current (dependent on my voltage supply strength). It seems to be still functional after that as the current was limited.
Best Answer
Most MOSFETs have a protection circuit between the Gate and Source, consisting of back-to-back Zener diodes and series resistance. In this case it is shown in the datasheet:-
The protection circuit is usually included to prevent damage from static discharge during handling, not to clamp excessive voltage during normal operation.
Your FET has no specification for current through the protection Zeners, so you must assume that any significant amount could kill it. However the most common failure mode is a short, so if your FET is still working properly and within its specs (particularly Gate-Source leakage current) then it is probably OK.