MOSFET Gate Ringing

[Bruce Sparrow]

#25810

I had a gentleman who had a power MOSFET and was complaining about ringing on the gate at 1-50MHz. I immediately began discussing beads to calm the ringing down. After some thought I responded:

“Miller Capacitance can be a problem where ringing on the drain couples to the gate. True gate ringing is caused by an LC circuit from driver to gate capacitance. A small impedance damps it fairly easily. Gate ringing beyond this may be caused by the above mentioned drain-to-source capacitance. Fixing the drain ringing (snubber) is the solution. Ferrite can help there as well. 1 to 50MHz is well handled by our 31 material but it is subject to DC currents so our 43/44 material may actually work better if there is significant current.”

Turns out that gate ringing was the symptom, not the problem. And we should never discount ground-bounce, as well!

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