Bob Axtell wrote:

> Rich Graziano wrote:
> 
>> I apologize if I missed some basic part of the problem, but is the
>> transient the result of the fast rise or collapse of flux of the relay
>> coil, which is what generates the transient spike?  [...]

> Er, well, the recommendation was made that a 1N4148 would suffice as
> transient protection to a 2n3904 transistor. 
> 
> I challenged that- my experience was that while problem-solving on a
> troubleshooting contract, I found a high- volume customer using 1N4148
> across a relay that were failing by punch-through (shorting). [...]

> That's the story. 

And the rest of the story was trying to figure out why exactly those 1N4148
fail or failed; IOW what exactly happens in that brief time between
something switching off the relay current and the diode conducting
normally. It seems that most of the explanations for this are based on
assumptions and nobody has really hard knowledge or could dig up relevant
semiconductor specs.

Gerhard

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