How To Test Any Mosfet Using LED
Internal diode is for to prevent reverse current which becomes reverse-biased and blocks current when the polarity of the applied voltage is reversed.
Sharing Easiest way to test MOSFET using LED Bulb:
We can use 3v to 5v supply Battery or any DC adaptor for this circuit in addition just required LED & resistor if using High voltage input like 9v or 12v for testing. This Circuit will help to detect Open Circuit, Short Circuit, Leakage or fail under the Load.
1) LED is ON by triggering the Gate and the LED is off when discharging the Gate, it shows that the MOSFET is Ok and it is in working condition.
2) LED remain ON indicates shorting.
3) LED remain OFF indicates Open circuit.
4) LED Glowing Dim / flickering indicates Leakage.
5) LED ON/OFF switching pattern is not according to gate triggering and discharging indicates intermittent working problem.
You can understand how to trigger Gate & Discharge Gate as per following diagrams.
For P-channel Mosfet testing refer to Given P-channel Diagram.
This article was prepared for you by Yogesh Panchal who works as a Computer Hardware Engineer in Mumbai India.
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Note: You can check his previous repair articles on CIRCLE PC ATX SMPS Model CPH698 Repaired
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Parasuraman S
September 28, 2025 at 5:28 pm
Very useful article and many thanks for sharing!
Yogesh Panchal
October 8, 2025 at 8:55 pm
Thank you! Sir
brian
September 28, 2025 at 6:14 pm
Hi yogesh.
I liked the fet testing method very much
I will look forword for more component testing from you in the future.
Yogesh Panchal
October 8, 2025 at 8:57 pm
Thanks!brian,
some tricks are out of the box & i also like to share.
Waleed Rishmawi
September 28, 2025 at 6:30 pm
the same testing could be done with a multi meter but thanks for sharing. have a blessed day
Yogesh Panchal
October 8, 2025 at 8:57 pm
Thanks! Waleed
Albert van Bemmelen
September 28, 2025 at 7:48 pm
No doubt very useful for those without any equipment at home. But in my case it is just easy plugging in any of my available semiconductor or curvetracer testers. Which also gives additional information on HFe and other values.
Yogesh Panchal
October 8, 2025 at 8:58 pm
Albert,
Thanks! for your input
tree
September 28, 2025 at 8:34 pm
Creative article, thank you.
Yogesh Panchal
October 8, 2025 at 8:59 pm
tree,
Thanks!
Mark J
September 29, 2025 at 12:04 am
Yogesh thank you for sharing.
Yogesh Panchal
October 8, 2025 at 8:59 pm
Your welcome! Mark J
Wislon
September 29, 2025 at 6:57 am
Thank you Yogesh, for this useful Mosfet testing technic
Yogesh Panchal
October 8, 2025 at 9:00 pm
Your welcome! Wilson
Kenkenny
September 30, 2025 at 1:02 pm
Thanks very much for the information
Yogesh Panchal
October 8, 2025 at 9:00 pm
Your welcome! Kenkenny
Muykit
October 1, 2025 at 1:45 pm
Very useful tip, Yogesh, for tesing and determining pin functions.
Yogesh Panchal
October 8, 2025 at 9:01 pm
Thank you! muykit
Derek Nathaniel
October 1, 2025 at 2:36 pm
Very useful article
Yogesh Panchal
October 8, 2025 at 9:02 pm
Thanks!Derek Nathaniel