I'm looking for a few MOSFETs for a really small motor. This question is exactly what I am asking but I'm afraid this might be marked as a duplicate.

Basically, I have really small motors rated more or less 1A 3.7V. The answer provided in the question was to use a SSM3K123TU mosfet but I'm having a hard time looking for the specific piece. What I found instead while roaming around eBay were these:

I'm guessing that these are extremely overkill for my purposes, but I might be wrong. I'm just looking to control a 1A 3.7V motor using PWM. I'm concerned that these might be too inefficient and there might be smaller ones available.

Are these okay to use with a small load or should I go look for smaller ones?

This might/might not help:

Power source: 3.8V to 5V

Max motor current: <1.5 A


1 Answer 1


I'm not going to do a direct answer: -

A good start is to look at absolute maximum voltages and current and check that any potential MOSFET you choose is ~ twice as good as what you believe you need for your circuit.

Next, I'd look at what the SSM3K123TU device does for you and this graph is very important: -

enter image description here

It tells you plenty of things about how good it will be at delivering power to the motor whilst not getting too warm itself. For instance, with a 1.2 volt gate-source drive and a 1A load (motor) you might expect to see an 70mV drop across the MOSFET. This is a power dissipation of 70mW. However, if your circuit could drive the gate with 4 volts, expect only a 20mV drop across the MOSFET when delivering 1A to the motor.

So that's it in simple terms - choose a MOSFET that matches what the SSM3K123TU delivers in these respects and you are likely to be able to make a long list of potential mosfets turn into a short list.

  • 1
    \$\begingroup\$ So basically, I can choose whatever mosfet I want, as long as it can accommodate my needs. Is that right or is there something horribly wrong with what I just said? @Andyaka \$\endgroup\$
    – Aloha
    Commented Sep 3, 2015 at 11:04
  • \$\begingroup\$ As an addendum to this - the first sentence of Andy's answer should help you immediately eliminate one of the MOSFETs you proposed in your initial question. \$\endgroup\$
    – stefandz
    Commented Sep 3, 2015 at 12:02
  • 1
    \$\begingroup\$ @PandaLion98 understanding your needs is the hardest part usually. \$\endgroup\$
    – Andy aka
    Commented Sep 3, 2015 at 12:55
  • \$\begingroup\$ Alright, if you want to be pedantic, the first line containing technical information. \$\endgroup\$
    – stefandz
    Commented Sep 7, 2015 at 8:38

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