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Argus25 · 7th Oct 2019, 7:09 am

I remember about thinking of the issue of reverse breakdown in the past because there are a number of publications explaining the severe destruction when it happens. However it isn't always. It depends on the product of voltage, current and time whether or not the junction spectacularly melts and it goes up in a puff of smoke, after all this is how Zener diodes work. You will notice though that Zener diodes over 100V are becoming difficult to get, when zenered just 100mA will cook them quickly.
There was once made a spectacular stud mounted 400V Zener, made by Lucas semiconductors, to protect the collector circuit of a transistor switching an ignition coil. They are so rare now I only have one in my collection and they never appear as a separate item for sale. Manufacturers wised up and use much less robust zeners between the collector and base of the output transistors, turning those in an active power clamp instead.

7th Oct 2019, 7:09 am	#4
Argus25 No Longer a Member Join Date: Oct 2016 Location: Maroochydore, Queensland, Australia. Posts: 2,679	Re: It's Smoke that makes it all work I remember about thinking of the issue of reverse breakdown in the past because there are a number of publications explaining the severe destruction when it happens. However it isn't always. It depends on the product of voltage, current and time whether or not the junction spectacularly melts and it goes up in a puff of smoke, after all this is how Zener diodes work. You will notice though that Zener diodes over 100V are becoming difficult to get, when zenered just 100mA will cook them quickly. There was once made a spectacular stud mounted 400V Zener, made by Lucas semiconductors, to protect the collector circuit of a transistor switching an ignition coil. They are so rare now I only have one in my collection and they never appear as a separate item for sale. Manufacturers wised up and use much less robust zeners between the collector and base of the output transistors, turning those in an active power clamp instead.