Hello All, Is it necessary to put a resistor on each gate when paralleling mosfets? Why is it necessary or not? If not necessary do you have to adjust you r value for 2 mosfets?

 

I have read both ways. I believe it is better to put a resistor (very low tolerance) on every gate, to ensure equal current to each gate, to charge gate capacitances and turn on all fets at the same time. Some people will say to use one resistor, but I don't remember the logic behind that, and it didn't sound right when I read it.

 

The primary purpose of the gate resistor is to kill the Q of the gate wire inductance. Otherwise, ringing and even oscillation can occur. To be most effective, it should be mounted as close to the gate as possible. With multiple transistors and only one resistor, it would be difficult to keep the distance between each gate and the resistor very short. Also, to maintain fast trnsition times, the resistor value would have to be lower, making the Q higher (I think).
I would use a resistor per gate.

 

Additional information can be found here:

http://hmin.tripod.com/als/ccs/docs/pdf/Fairchild_AB-9.pdf

and here

http://www.microsemi.com/en/sites/default/files/micnotes/APT0402.pdf

 

I appreciate the help. I have been Googling for a while. Learned a lot but just couldn't find very much information on that subject. The links from praondevou are exactly what I was looking for.