Hi all, I have a project where I'm putting up to 10 amps through a NFET=20 connected to ground as per typical. Things are working fine except I'm=20 seeing a much larger temperature rise in the FET than expected. The FET is Toshiba TK100E06N1,S1X Datasheet: @ digikey: The specs say 2.3 mOhm @ 50amps@10V (from digikey info) and 1.9 mOhms=20 typical from the datasheet. I'm driving it with a gate driver running=20 at approx 9V. At full on (i.e. no PWM, to keep it simple), with 10amps going thru it=20 (I've measured reasonably accurately), I'm getting something like=20 90-105deg C operating temperature. I have a thermistor bolted onto it=20 and an IR thermometer and they're giving in the same range. And it is=20 definitely is ding dang owie hot. The question is: why so hot? The transistor is not heatsunk, on a pcb=20 in open air on the table. (No enclosure for now.) Power =3D Current * Current * Resistance, so for 10amps, P=3D 10A*10A*0.0023R=3D 0.23W of heat should generated by the FET. Right? In datasheet, section 5 page 2, we get "channel to ambient thermal=20 resistance" of 83.3 degC per watt. Figuring 25deg C ambient, it should=20 get to: 25degC + (83.3degC * 0.23) =3D 25 + 19 =3D 44 deg C. Right? But I'm getting 2X that. Now fortunately this FET (like most others) runs to 150degC, and a=20 heatsink can be added in this design without undue suffering. But I=20 don't get it, and of course that worries me a little... Where am I going wrong? I just verified the gate is indeed being driven=20 at 9V. The system voltage is 12V, and this is a LED dimmer so the=20 configuration is: power supply's +12V -> LED strip -> NFET -> ground.=20 I'm not doing PWM in this setup to keep it simple. I have two protos and they both behave similarly. And another FET by a=20 different manufacturer is also running 2X hotter than expected, so I=20 think I have a comprehension problem... Cheers all, and thanks in advance yet again. J --=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 .