Question about MOSFET testing with DMM.

Thread Starter

UnnamedUser159

Joined May 3, 2016
501
i friend of mine told me when i make short between G and S with tweezers(i am using antiES gloves) to measure resistance D<->S and in one direction "it can be small resistance" but the other one "should be very high"

very high should be with negative probe on Drain and positive probe on Source, right?

thanks
 

MrChips

Joined Oct 2, 2009
23,958
I test MOSFETs by applying power to the DRAIN and SOURCE via a load resistor at the DRAIN.

Then I apply a square wave signal from a function generator to the GATE while observing the voltage at the DRAIN on an oscilloscope.

I adjust the square wave amplitude and DC offset in order to determine the turn-on threshold voltage.
 

Reloadron

Joined Jan 15, 2015
5,998
You may want to give this a read as it gives a pretty good and brief overview of very basic resting of P and N channel common MOSFETs. While using a DMM will help it won't always tell the full story. My experience overall is when a MOSFET fails it normally fails with a source drain short. Not always but for the most part.

Ron
 

Thread Starter

UnnamedUser159

Joined May 3, 2016
501
Now i have one board installed on monitor power/inverter board and want to check the starting up transistors. Have desolder one and there is no short between D and S. How to be sure it`s not failed to continue calmly analyze board?

:)
 
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