Test with a multimeter

P-channel MOSFET

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Now: Body diode: red on D, black on S

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Pin 1: Gate (G) (G) Pin 2: Drain (D) (D) Pin 3: Source (S) (S)

Red probe Not connectedBlack probe Not connected

Hold the probe and drag it to the tip of a leg. Tapping works too: first pick the probe, then the leg.

Set the range to diode test.

Measure step by step

In a P-channel MOSFET the source is on the plus side. The body diode conducts from drain to source; the gate is insulated. This guide uses the IRF9540N leg order from the Atlas.

Static electricity can damage a MOSFET’s gate. Before measuring, touch the pins together for a moment to discharge the gate.

  1. 1Body diode: red D, black S
  2. 2Reverse direction: red on S, black on D
  3. 3Gate to source
  4. 4Gate to drain