How to Identify the Pinout of a MOSFET

Updated February 26, 2018

If you're building a new circuit or repairing an existing one, you may need to identify a MOSFET's pinout configuration. MOSFETs, or Metal-Oxide Semiconducting Field-Effect Transistors, are three-pin devices used in power amplifiers, switching circuits and other applications. The three pins are called source, gate and drain. Within a particular package style, most manufacturers use the same layout. A data sheet, however, helps in identifying the device's pins.

Connect the antistatic wrist strap ground wire to a solid electrical ground, such as a conduit pipe. Slip the strap onto your wrist.

Examine the MOSFET transistor. One side of its body will have a printed part number and other identifying information, such as the manufacturer's logo. If the letters "G," "D" and "S" appear over the pins, these letters identify the transistor's gate, drain and source leads. If you don't see these, continue to the next step.

Read the MOSFET's data sheet. It will have sketches or pictures of the device with the pins labelled for gate, drain and source. Grasp the MOSFET and orient it as it appears in the diagrams. Match each pin in the drawing with the pin on the actual device and note which are gate, drain and source.


MOSFETs are voltage-sensitive devices. Static electric charges in your body can easily damage a MOSFET. Before handling, wear the antistatic wrist strap to drain static from your hands.

Things You'll Need

  • Grounded antistatic wrist strap
  • MOSFET transistor
  • MOSFET transistor data sheet
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About the Author

Chicago native John Papiewski has a physics degree and has been writing since 1991. He has contributed to "Foresight Update," a nanotechnology newsletter from the Foresight Institute. He also contributed to the book, "Nanotechnology: Molecular Speculations on Global Abundance."