How to check if a MOSFET is bad

We are going to explain to you how to check if a MOSFET is bad, and MOSFET is a common electronic component we used in most applications.

But most of us don’t know how to check a MOSFET and confirm them works well or is bad, in this article we are going to list some common MOSFET checking procedures using the multimeters.

Check if a MOSFET is bad

Before going to the checking procedure of MOSFET, we need to know some of the common failures that happen at MOSFET.

  • One of the most common failures in MOSFET is the gate-source breakdown, this can easily determine by setting the multimeter in resistance mode.
  • We know that MOSFET had a body diode internally, so we can check the body diode is faulty or not by connecting the multimeter into MOSFET’s source to drain terminals (resistance mode).
  • And the MOSFET can handle high temperatures, the fault-finding due to temperature rising will be check with the diode mode of the multimeter.

Diode check

  • We need to set diode mode at multimeter to check diode, if a reading appears without any variation, the MOSFET is good.
  • Or if the meter indicates zero, MOSFET is faulty.
  • And also this process will be the same for all MOSFET types, but with different probe connections.

Resistance check

  • We need to set the multimeter in resistance mode and connect the probes between the drain and source terminals of MOSFET.
  • If a multimeter indicates high resistance, which is a clear indication for a good MOSFET.
  • If the multimeter indicates zero, the MOSFET is faulty.

Continuity test

  • We need to set the multimeter in continuity mode and connect the positive to drain and negative to the source.
  • If the reading will be zero, with a buzzer sound, the MOSFET is faulty.

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