I need to switch a number of solenoids from a PIC, and the solenoids =20
will be normally-off unless told otherwise.  I'm considering on-board =20
relays vs. MOSFETs.  MOSFETs would be nicer due to the smaller space =20
requirement, but I understand that in case of failure, MOSFETs usually =20
fail closed whereas relays usually fail open (unless contacts get =20
welded, etc).

How true is this?

I'd think perhaps I can come up with some arrangement of two MOSFETs =20
in series to drive each solenoid (for much higher reliability), but =20
that drives cost up noticeably, and then I'm not sure there'd be any =20
space benefits.

Are there any special MOSFETs that are different in this respect?

Thanks,
-Neil.


--=20
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