Are FET gate resistors always necessary?

Thread Starter

Robin66

Joined Jan 5, 2016
275
Hi. I have the following layout where U1 is a IR2101 gate driver and I've highlighted the connection to the lower FET's gate. Now you can see that if I ditched the resistor highlighted then the connection would be ~2mm. My understanding is that gate resistors can reduce EMI by slowing dV/dt, and they reduce ringing and thus overshoot by lowering the Q of Cgate-Ltrack. However you can see that if I remove the resistor then Ltrack will be negligible, and I believe that U1 will handle the increased power dissipation, and I can improve the decoupling to mitigate the EMI.

Is this acceptable or am I creating problems for myself?


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GopherT

Joined Nov 23, 2012
8,009
The EMI is not from the act of turning the gate on, it is the result of slamming the gate on/off which slams a high current DS connection on/off.

If you don't care about EMI, or you are not driving anough current through the mosfet to create significant EMI, then no problem...
mostly. Without a gate resistor, there is nothing to give resistance to the gate driver so you will likely exceed your gate driver's current limit as the gate capacitance is charged.
 
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