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How to Check Mosfet

Transistors are semiconductors whose purpose in circuits is to provide switching or amplification for electrical signals. FETS are a special type of transistor. Regular transistors require different semiconducting using two types of charges, but FETs rely only on one. They have either electrons that have a negative charge, or holes that have a positive charge. MOSFET stands for metal-oxide-semiconductor FET. They are very small, and don't require much power to operate.

MOSFETS are very sensitive to static electricity, and can easily be destroyed by sources such as clothing, plastic or fingers. For that reason, they must be tested for damage. To check a MOSFET, use a digital multimeter.

Things You'll Need

N-channel MOSFET
MOSFET data sheet
Digital multimeter

Instructions

- 1
  Determine which of the MOSFET leads are the gate, drain and source. This information is found on the package, manufacturer's website or data sheet.
- 2
  Check the resistance between the gate and drain. First, turn the multimeter on and switch it to a very high resistance setting in the megaohom range. Then, place one of the multimeter's probes on the gate lead, and the other on the lead for the drain. If the MOSFET is working, the resistance reading will be infinitely high.
- 3
  Turn the multimeter on the diode setting. This is represented with an arrow-like symbol that appears on the its case.
- 4
  Place the multimeter's black probe on the drain, and its red one on the source. The undamaged MOSFET will behave like a diode, and will be conducting. Reverse the probes, and it will be non-conducting.
- 5
  Activate the MOSFET. First, leave the black probe on the source. Next, briefly touch the red probe to the gate, and then place it on the drain. The multimeter reading will be in the low millivolts. A representative one for an IRF510 is 0.025 volts or 25 millivolts.
- 6
  Discharge the MOFET. Leave the red probe on the drain, and remove the black probe from the source. Next, touch the gate and source with a finger. When the black probe is placed back on the source, the multimeter display will show that the MOSFET is once again non-conducting.

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