How to test FET’s-Jfet and Mosfet

jojo September 8, 2009 5 Comments

All the testing methods below uses a multimeter and hence its How to test FET’s especially the JFET and MOSFET using a multimeter.

How to test an FET ?

FET testing method

FET testing method

FETs are checked by measuring different resistances by a multimeter. When resistance is checked between source and drain, it should be of the order of 10 kohms.

How to test a JFET ?

JFET testing methods

JFET testing methods

When a JFET is checked as a diode (gate-to-channel junction) multimeter should indicate low resistance between gate and source with one polarity and very high resistance between gate and source with meter polarity reversed.

Troubleshooting a JFET test

If the meter indicates high resistance with both the polarities, it means that the gate junction is open. On the other hand, if meter indicates low resistance with both polarities, it means that the gate junction is shorted.

How to test a Mosfet ?

Mosfet testing methods

Mosfet testing methods

While checking MOSFET, the resistance measured between gate and drain should be infinitely high in either polarity. Low resistance means faulty device.

  • Dunesh
    July 7, 2014

    Image is not visible for “Mosfet testing methods”. I think it is not there in directory tree. Please update it as soon as possible.


  • abdulmumini
    May 26, 2012

    is the channel a separate lead?jfet is 3-terminal component.I.e gate,drain and source.the phrase measuring resistance between gate and channel is not clear

  • mukesh kumar kamboj
    February 12, 2012

    i am not clear the mosfet testing

  • hassan
    October 1, 2010

    please subscibe me in your news letter

Leave a Reply