Failure measurement MOSfets

[Martinsson]

Hello everybody.

I was wondering if there is an easy way to check if a MOSfet is faulty.
Without having the electic system running I mean.

Martinsson

 

[trapoe]

There is mainly three way to break a MOS:
1) interrupt the channel between D and S
2) shorting channel between D and S
3) breaking gate oxide

you can try to check with a simple ohmmeter:

1) set for checking diode, connect positive of ohmmeter on S and negative on D, you should find around 0,4 V. If you find open probably channel is broken

2) simply measure resistance connecting positive on D, you should find high resistance. It depends on what is connected to MOS of course. If you find short then probably MOS is faulty.

3) check isolation between G and S. You have to find resistance added by external circuit (look for resistors between G and S). If it's shorted probably MOS is broken.

Hope this will be clear.