The circuit below will drive a 12v motor using an optocoupler. In the circuit PC817 is used but how do you know which optocoupler to use?

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    \$\begingroup\$ Possible duplicate of How to drive a MOSFET with an optocoupler? \$\endgroup\$
    – Bort
    Jun 13, 2016 at 19:01
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    \$\begingroup\$ What are your requirements of the signal properties at the gate? Same goes for the signal properties at LED side of the optocoupler, what current/voltage? Is it on/off switching or is there a period linear driven signal? Figure out you input spec and your output requirements, only then start to think how to solve the in-between. \$\endgroup\$
    – jippie
    Jun 13, 2016 at 19:16
  • \$\begingroup\$ @Bort. OP seems more concerned with choice of opto-isolators than driving the mosfet. The PC817 is only 55 cents or so in cost and has an isolation barrier of 5KV. Typical LED current is 5mA. If the OP reads the datasheets of this and other optos they would understand why this is a good choice over a hundred other opto-isolators. \$\endgroup\$
    – user105652
    Jun 13, 2016 at 19:43
  • \$\begingroup\$ Questions seeking recommendations for specific products or places to purchase them are off-topic in this forum. \$\endgroup\$
    – tcrosley
    Jun 13, 2016 at 20:45
  • \$\begingroup\$ Please be more specific: electronics.stackexchange.com/help/how-to-ask A professional question will get a professional answer \$\endgroup\$
    – Voltage Spike
    Jun 13, 2016 at 22:15

1 Answer 1


Start by choosing a "gate drive" push-pull optocoupler and you almost can't go wrong. I would choose one with a supply voltage of 30 volts or so to give yourself some margin running a motor. You may need a resistor on the input side to limit diode current. The PC817 you have chosen is a poor choice for anything except a low speed, on-off switch because when you turn it off, you are relying on the 10K pull-down resistor to drive your MOSFET gate.


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