Transistor and different power source

mikea

Can i use 2 different power sources with a transistor, one source to control the base say 3.3volts and 24 volt for collector/emitter? I dont want the 24volts to affect or get to the 3.3 source (propeller pin). Also this question goes for an n channel mosfet....is this a safe setup for either a transistor or mosfet?

Peter Jakacki

It's fairly common to do so as in the case of driving a transistor from 3.3V logic which then switches a much higher voltage and current. Nch mosfets are much preferred for heavy loads. The real question about more than one power supply is where to common them up safely as you have to think of ground leads as having to carry all the current of that load which may result in frying or affecting your logic if that current ends up flowing through the logic circuits. Run the ground for the 24V side back to the 24V supply and connect the logic ground to the mosfet, that way the 24V load current will not pass through any logic including the logic ground.

erco

You could also use an optoisolator to keep your circuits completely seperate, not even sharing a common ground.