>
>
>
>
>
>
>> >> - Bargain-price/cheapie/fallout zeners diodes are basically units that
>>
>> >> fail to pass the manufacturer's final test. I was given a box of them
>> >> which was marked "semiconductor scrap". Some were usuable. Some were
>> >> not. None were first class.
>> >
>> > <snip>
>> >
>> >> quality semiconductors.
>> >>
>> > <snip>
>> >
>> > ::I wonder: What is the difference in "quality" between fallout and
>> >first-class, in Zeners?
>>
>> A mixed bag.
>>
>> >Having fabricated a lot of these (starting with
>> >undoped silicon), the "fallout" in manufacturing is usually -- oops!
>> missed
>> >the target avalanche voltage! -- or -- oops! failed to meet another
>> >parameter such as leakage current below avalanche, or dynamic impedance
>> >(slope of Vz/Iz).
>>
>> Inability to maintain constant V with <> I is the sticky wicket.
>>
> ::Well, dynamic impedance, which is the parameter of which you speak
>(write), is a function of only three variables: Avalanche voltage; junction
>construction; junction cross-section (die area). If one desires low Zz
>(dynamic impedance), it's easy to find in very large-area devices, such as
>100W stud devices. Placing a bunch of low voltage avalanche devices in
>series increases Zz by a factor of how many diodes are placed in series.
If the delta V for one diode ia 2%, the delta V for 100 of them in series
is 2% even though the regulated V is 100x higher.
>(Icall these avalanche devices instead of Zeners, because, technically, all
>"zener" devices having an avalanche voltage above about 5.6V are not really
>Zeners;
Good point, Steve.
> their coefficient of breakdown voltage is proper for an avalanche
>diode, but reversed from that of a Zener device.)
>
> -WB2WIK/6
>
>
>
>> cheers, Steve
>>
>> >...
>>
>> - R. L. Measures, a.k.a. Rich..., 805.386.3734,AG6K,
>> www.vcnet.com/measures.
>> end
>
>--
>FAQ on WWW: http://www.contesting.com/FAQ/amps
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>
>
- R. L. Measures, a.k.a. Rich..., 805.386.3734,AG6K,
www.vcnet.com/measures.
end
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