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I've this circuit and works correctly, now I need to control 4 MOSFET instead of 2, is the second schematic correctly? enter image description here

enter image description here

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  • \$\begingroup\$ How is that +12V related to the MOSFETs? What switching speed are we talking about? \$\endgroup\$
    – winny
    Commented Mar 3, 2021 at 13:01
  • \$\begingroup\$ this circuit needs the mosfets to switch once every 5 minutes (not pwm, that's why I didn't put a driver), does 12V reach all gates? \$\endgroup\$ Commented Mar 3, 2021 at 13:07
  • \$\begingroup\$ Yes, I think PC817 can drive many more than 4 MOSFETs. \$\endgroup\$
    – tlfong01
    Commented Mar 3, 2021 at 13:15
  • \$\begingroup\$ If you don't mind that switching takes up to a second then the PC817 can switch hundreds of MOSFETs. Realize that MOSFETs have a high impedance input (gate) and behave largely as a capacitor (to the source). \$\endgroup\$ Commented Mar 3, 2021 at 13:49
  • \$\begingroup\$ You didn’t answer my question: What’s the relationship between +12V and A-, B-, OUT1 and OUT2? \$\endgroup\$
    – winny
    Commented Mar 3, 2021 at 16:20

1 Answer 1

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this circuit needs the mosfets to switch once every 5 minutes (not pwm, that's why I didn't put a driver), does 12V reach all gates? – Ricardo Casimiro 4 mins ago

Yes all the current is drawn by the 10k resistor to 11.7V with Vce(sat) on the opto. or > 1mA

This works well with 4mA input or more.

If using 3.3V input (3.3V-1.2)/(220+25 cmos) = 8.5mA

If using 5V 220 Ohms is overkill but OK.

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