zener diode pulse current rating

I knew one, long ago. It was just around the time power MOSFETs became common, even though they were still expensive. He was testing some and he had a whole heap of devices that "didn't conform to specs". You'd think that after a pop or two he'd start to wonder if he'd misunderstood something, but not this one.

Oh well, I thought it was funny. No idea what's become of him. Popping GaN transistors somewhere, probably.

Jeroen Belleman

SOA isn't about (not) using a device at max voltage and max current. The max power spec says you can't do that (unless it's an IRC part ;-). SOA is about transitioning between the two safely. ;-)

One project I was sucked into turned out to be a SOA problem that the more senior engineer in the group designed in. Because of some completely avoidable design decisions, he put freewheeling diodes across contactors instead of across the transistors driving them, some 20' away. In one series of mainframes the wiring inbetween was just "black wire" (basically a wad of individual 24GA wires) which was quite inductive. Oops. The other two models used twinlead or trilead between the two points, which was quite capacitive. No problems with them. One brand of drivers (Motorola) would go through secondary breakdown and fry, causing the contactors to fail closed and the magic smoke to roll out of some ballast resistors. Not so good. I proved that Sprage devices would never fail (without avalanching first), so that was the fix. Not the best, but it worked.

Don't understand the above paragraph.

Now comes the argument about what constitutes "WAY beyond specifications". ;-)

Ah, but you see.. I would never insult the word "rational" by using it to describe most of the engineers here :)

Tim

Sprague