> I'm purposely driving this at ~90% duty cycle, to see how much heat > would be dissipated in worst-case operation. I would guess that the duty cycle might be irrelevant. It's the quality of the transitions that matters. If it's anything but an 'instant' and single= =20 L-H or H-L then there's going to be heat because time is being spent in the FET's linear region. All these extra components around the FET are an attempt to minimise undesired transitions without slowing down (ie keep the slopes as vertical as possible) the required ones Joe=20 ----- No virus found in this message. Checked by AVG - www.avg.com Version: 2016.0.7227 / Virus Database: 4460/11068 - Release Date: 11/26/15 --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .