Sounds more like you need the good luck! Have you looked at IGBT's. You should be able to get one to switch OK in your timeframe but they are somewhat better at handling higher voltages. There's an IR aplication note about using IGBTs for ignition systems that may be applicable. One possibility is that your FET is getting hot because of ringing or even oscillation - a well designed snubber will do wonders here without killing your risetime. Putting a 12V or so zener on the gate of the FET may assist in protecting it. Richard P I am switching an inductive load (coil on a metal detector) with 24 volts switching through the coil and an inductive spike that reaches avalanche at over 400V. I'm using an IRF740. I put an IRF840LC low capacitance version in my circuit and inductive kickback was at 650V but didn't reach avalanche. I had to put a hefty heatsink on it because it gets so hot. I'm pulsing it with 200us on time but am going to increase it so I'm moving to a heavier FET in a TO-247 case. All these FETs are rated for 10V gate voltage. Good luck >From: Richard Prosser > >You do not need a Vgs of this order. >The Gate voltage is what turns the FET on and normally 12V is more than >enough to do the job. >The Vds rating needs to be greater than the voltage you are switching - >possibly much greater depending on the nature of the load (e.g. inductive >loads will generate voltage spike 20 times the supply voltage without too >much difficulty.) > >The device also needs to be able to handle the peak and average load >current being switched and must have sufficient heatsinking and power >capability to ensure that the die temperaure does not exceed its maximum >rating. (150 - 175C) > >I can't be more specific without more info - what is your load, your load >current, your switching rate and what are you planning to drive it from. - >and what environment is it operating in? > >Richard P > snip..... -- http://www.piclist.com hint: To leave the PICList mailto:piclist-unsubscribe-request@mitvma.mit.edu