I need a high current carrying mosfet for some application. What will be the challenges if I use 2 or 3 mosfets in parallel,
Not much. That works with BJT but not with MOSFETS.an equal low value source resistor with each FET will help
Those MOSFETS should be driven on as hard as possible even in the worst case, so yes, a driving variation of .1 volt shouldn't make a bit of difference there.Not much. That works with BJT but not with MOSFETS.
Yeah, you need the small resistor with BJTs to current balance since BJTs conduct better as they heat up which causes the most efficient BJT to take up more and more of the shared load (positive feedback due to a negative temperature coefficient) cycle until it blows.I think this project is about running great amounts of current. Any voltage across a Source resistor will heat. Efficiency is important.
I just pulled a data sheet for a large high voltage MOSFET. Its on resistance goes up when hot. If one FET takes most of the current, I think it will heat and increase resistance thus shifting the current more to a second part.
Data sheet: Max resistance = 0.25 ohms, Typical resistance = 0.19 ohms, Min resistance is unknown so I will pick a number (0.125 ohms).
Extreme example: Take a 0.25 in parallel with a 0.125 and one MOSFET has 10A while the other has only 5A. Sharing is not so good in the extreme example, but the 10A part will get hotter and shift some of the current to the colder part.
It is also hard to find the "best" and "worst" part in the same batch.