I have designed a circuit in which I have used a BSS138 N channel MOSFET as a switch to turn on a 12V 50mA load from a GPIO.

During the schematic design in KiCad, I have chosen the wrong symbol.

These are the options available in KiCad for N channel MOSFETs.

Options in KiCad for NMOS

The symbol I have chosen has Gate at Pin 1, Drain at Pin 2 and, Source at Pin 3. Whereas BSS138 has its Gate at Pin 1, Source at Pin 2 and, Drain at Pin 3.

KiCad symbol difference

I just realized this blunder while I was checking why the load was always ON. Based on a suggestion, if I bend the pins the other way and solder it upside down, it's working well. But I would have to do this modification to a whole batch of PCBs.

Is there a common N channel MOSFET that has such a pin configuration with similar specs as BSS138 that I can use as a replacement? I have searched on Digikey and Mouser but I couldn't find any. I couldn't even find a filter for such a pin configuration. Open to any and all suggestions.

  • 1
    \$\begingroup\$ This is the most common pinout for MOSFETs; almost any FET in TO-220, TO-247, DPAK, D²PAK, SOT-89, or SOT-223 will be GDS. It's basically only the SOT-23/323/523/723/923 ones that have the GSD ordering--which is more because of the different pin numbering convention for those packages than anything else (the physical pin layout is the same). \$\endgroup\$
    – Hearth
    Dec 6, 2023 at 14:45
  • \$\begingroup\$ Oh! Understood. \$\endgroup\$
    – WhiteShark
    Dec 6, 2023 at 18:39
  • 1
    \$\begingroup\$ You haven't indicated what actual footprint you put on the PCB (or that you exactly laid out and fabbed a PCB, for that matter), so one could correctly answer with any packaged device that applies (see above) -- are you sure? If not, please edit your question to be more specific. \$\endgroup\$ Dec 6, 2023 at 19:34


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