Arfa Daily wrote:
"Phil Hobbs" wrote in message
...

Dave Platt wrote:

flywheeling diode and a 1N4007 would do the job just fine. Does the FET
source go to ground ? Many power MOSFETS have a diode internally in that
orientation across from the source to the drain. It gets there as an
integral side effect of the manufacturing process.

Newer designs seem to use a fast-recovery diode (e.g. FRED or HEXFRED
or HiperFRED) for MOSFET flyback protection. 1N4007s aren't
particularly fast, and reverse-conduction losses can be significant if
the switching frequency is high (in e.g. an SMPS). That's probably not
all that much of an issue in a solenoid driver, though.


1N4007s can take a long time to turn _on_ as well as off. You can get
several volts of overshoot in some applications. Definitely not your
ideal catch diode.

Cheers,

Phil Hobbs


But one that is used by manufacturers world wide for exactly that purpose
...

Arfa

so? just because it gets used doesnt mean its suited for the task. think
bell curve....


BTW in that position its probably a 47V zener, clamping the peak drain
voltage.

Cheers
Terry