I worked in the discrete semiconductor industry for 30 years (engineering, manufacturing, management) and that statement is simply not true at all.
Zener diodes are designed to break down uniformly across the entire junction, but most other semiconductors are not. A reverse voltage breakdown of the collector-base junction will in most cases force current through an extremely small region of the junction (often referred to as a "puncture") and fuse the silicon at that point, rendering the device useless. The current required to do so is much less than would be required to heat the device even a few degrees, and the time required to destroy the device is short. Junctions with steeper diffusion gradients (RF devices, switching transistors, etc) will fail more easily (sometimes in microseconds), while sloppier junctions (power devices, etc) will take considerably more abuse. It is not possible to predict the current at which catastrophic failure will occur. Emitter-base junctions are typically more graded and won't fail catastrophically as quickly, but repeated reverse bias conditions will degrade the transfer gain of the device by creating defect centers that kill the carrier lifetimes in the base region. The inductive kick from even a small relay is sufficient to puncture the junction of many commonly used transistors or driver ICs, and there are reams of failure analysis reports documenting that fact. There isn't a manufacturer on this earth that will honor the warranty for a device used as you describe unless the device was specifically designed to survive it. Dave AB7E Rick Shindley wrote: > What kills solid state PN junctions is excessive power dissipation (heat). > You can abuse the breakdown voltage of a PN junction as long as the power > dissipated there is within the power dissipation range of the PN junction. > That's how Zener diodes work and it is why they have a power dissipation > rating. All diodes will function as low-current Zener diodes if you manage > to provide a high enough reverse voltage across them to break them down and > limit the current so the power they must dissipate won't destroy the PN > junction. ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
