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On Wed, Sep 20, 2023 at 03:49 PM, Donald S Brant Jr wrote:

It's not always heat which causes failure.

Absolutely. Heat generally decreases MTTF and make the device more susceptible to other threats but heat alone is only a gradual and slow-acting cause of failure. In case of general purpose switching MOSFET, heat makes the parasitic npn transistor more likely to conduct and cause so called secondary breakdown. BS170 is supposed to be not very susceptible to that but we are also abusing it with fast and deep drive and lots of drain current so we should all keep that in mind.

A short circuit is not necessarily the worst load.

Absolutely. Another question is short circuit where? Shorting the BNC connector is not the same as RF shorting the drains on the die.

It is always tempting to over-simplify and/or trivialize complex problems but rarely the best approach.

I might add that the same applies to the brain science.