At 07:13 AM 12/28/2011, Electron wrote: >For this prototype, I had soldered the driver output pin directly on the >gate of the IGBT, and *this* caused the oscillations!! Yep! This catches a LOT of people who haven't dealt with fast FETs or=20 IGBTs previously. It certainly got me when I first dealt with such things. I generally use a low-value resistor (10R-47R), depending on the=20 amount of gate capacitance. But I think that your idea of using a=20 ferrite bead is better. One of my co-workers was working with some high-power stuff many=20 years ago and misunderstood my instructions when I told him to=20 install 47R resistors as close to the FET gate as possible - he had=20 long, meandering wires (6") that went from the FETs on the heatsink=20 back to his driver board. What he did instead was to put the=20 resistors at the driver board. The FETs oscillated and self-destructed several times before he asked=20 me for help. Simply moving the gate resistors back to right beside=20 the FETs (where they should have been) fixed the problem. The FETs were driving large wire-wound heating elements (800V, 30A)=20 and those heating elements were inductive as hell. dwayne --=20 Dwayne Reid Trinity Electronics Systems Ltd Edmonton, AB, CANADA (780) 489-3199 voice (780) 487-6397 fax www.trinity-electronics.com Custom Electronics Design and Manufacturing --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .