Re: Help understanding Darlington CB leakage current and its ramifications

Rich Grise wrote:
On Fri, 22 Jul 2005 11:15:39 -0700, gerbermultit00l wrote:

What's the actual load voltage?

Normal operation range 9VDC to 18VDC. Circuit must survive 100V transient for 400mS. Also 24VDC for 30 minutes.

Pick about a 30V or 33V one of those and put it across your supply
leads, maybe with a hash choke or some ferrite beads.

Good Luck!

Hmmmm. He must have some way to protect his low-level (micro) from transients because he is only worried about the relay's switch. So, why not put a 40V TVS from the FET drain (or darlington collectors) to ground? Nothing would happen for the 24V case and 60V of the 100V, 400ms transient would be dropped by the relay. The relay provides an impedance for the TVS to work with. The relay might pull in temporarily. This way, he could use a 60V FET and a really low power TVS.

Just an wild thought.