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Old 08-01-2009, 06:31 PM
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Harvey Harvey is offline
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Originally Posted by rave154 View Post

ive got hold of 3 IRF740's

they seem very comparable to the mosfet youre using, avalanche rated, diode inside etc.... will it suffice you think?

David. D
That part has a lower on resistance (good thing) but a lower Avalanche Voltage (400V instead of 1000V) So it will Avalanche with a lower spike level, but it does have a higher drain current (another good thing).

It's input capacitance is lower and it's output capacitance is higher. All the combined differences (esp. the on resistance) will cause it to act differently than Rosemary's circuit, but it (the circuit) probably can be adjusted to get the benefits sought after.

I'll be posting the section on Avalanche from the Designers Manual in a few minutes.

Last edited by Harvey; 08-01-2009 at 06:35 PM.