Author Options:

Will transistors in parallel hold up to a higher current? Answered

I'm trying to create a simple PWM speed controller.  The only problem is that this controller will need to be able to stand up to 100 amps (probably more, but let's just leave it at 100 for simplicity).  A typical 2n3055 transistor can stand up to 15 amps when properly cooled.  Will wiring 8 of these transistors in parallel be enough to stand the 100 amp current?


For this kind of current, and for PWM operation, I'd use a MOSfet and not a BJT, Mosfets, driven properly, don't need paralleling "degenerating" resistors. You need to look VERY carefully at the graphs of safe operating areas for the transistors. Steve

agreed. bipolars were used for years to do this, but they are grossly inefficient.

Thanks everyone for the comments. Like I said, I'm making a controller for an electric vehicle.  I'm using a car starter motor which I will salvage and according to what I've found out, a standard starter is rated 12 volts at 1.2kW.  Do the math and that comes out to about 100 amps, and more if I strain the motor.  Thanks Steve for reminding me of using MOSFETs.  I remember now what happened the last time I used a bipolar junction transistor to drive a moderate load (magic smoke).  I looked it up and found that MOSFETs handle a lot more current than BJTs.   Thanks again everyone.

What is the ~100A for? (interested) L

Mmm, it sounds "beefy".  But plain transistors won't do it very well. If you comment back to Steve he knows what he's talking about.



8 years ago

Well, it should..But don't forget to put an equal (small) resistor into each branch for better current distribution into branches..