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The spec sheet will refer to a PD  which is higher than our calculation. This is because it assumes that you can keep the MOSFET at 25C while operating which would mean you would need a heatsink.

Testing For Fake Mosfets

Testing Procedure

Using a 12V source and a automotive 12v light bulb:

  • connect up the bulb and record its current draw from the bulb and the voltage of the supply.

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To measure the Voltage from Drain to Source

  • connect negative to Source(S)
  • connect voltmeter as shown
  • connect the + side of the voltmeter to Drain (Bulb should be off)
  • connect the + side of the voltmeter to Gate (will activate the mosfet)
  • connect the + side of the voltmeter to Drain (Bulb should be ON)
  • record voltage

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Testing IRFP260


Voltage: 12.09v

Current: 2.00A

Voltage Drain to Source: 0.42v

Calculated R(ds)

R(ds) = Vds / I = 0.42v / 2.00A = 0.210 ohms

Datasheet Specs

R(ds) = 0.055 ohms




MOSFET Transistor
Real vs Fake MOSFET | How to identify a Fake Transistor? | MOSFET Test