I have two gpio pins (3.3V logic high) to control an LED indicator (includes 2 LEDs and one common ground). The supply voltage to turn the LEDs on is +12V. Is it possible to simple drive (3.3V logic from uController) the common ground device with two seperate P MOSFETs? If not, what circuits sequence I should follow?


1 Answer 1


It's a pity they are not common anode because then it would be easily done with two ground referenced n ch mosfets.

To do it with a common cathode circuit will work with two p ch mosfets but, for each mosfet you'll need a transistor to pull the gate down to 0v. This is because a gpio pin that is high will still keep the p ch mosfet turned on.

Basically an n channel fet and pull-up resistor can fully activate the p channel fet's gate.

There is another option of a zener level shifter but component values and selection may be tricky with only a 3.3 volt gpio drive signal. Still do able though.

Using bjts can work too.

  • \$\begingroup\$ Thanks, which option do you suggest by considering current consumption? \$\endgroup\$
    – ynan
    May 29, 2015 at 13:12
  • \$\begingroup\$ @ynan - I don't expect the current consumption of the "switching circuit" to be any more than 5% of the full load AND using FETs or BJTs will be about the same. Maybe FETs will be marginally lower. Using a zener level shifter will be slightly more power than a BJT. \$\endgroup\$
    – Andy aka
    May 29, 2015 at 13:15

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