>>> I have an amp that I have put several 5.6Volt @ 5watt zeners
>>> in series for cathode bias. They get way too hot with
>>> about 800ma of current. Can I parallel zeners to divide the
>>> current without problems with balance between them?
Tom Rauch wrote:
>>Hi Doug,
>>You should have enough headroom. That's only .8^2 * 5.6= 3.6 watts
>> per diode. Maybe the heatsink is too small, or mounting is incorrect.
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>
>
>
>> Does P equal I^2*R, Tom?
>
> Yes, actually, it does!
Bingo. Tom sez P=I^2*E. [see above quote] -- i.e., can both formulas
be true?
>
>> I thought P equals E*I = 4.48w.
>
> Also correct!
>
Does 4.48w = 3.6w?
ok
>
>> >You know diodes can run pretty hot and remain safe.
>>
>> Zener case temp is 25ºC/77ºF-max at rated dissipation.
>>
> Another point to ponder is that Zener devices have a TCZV which
>makes them drift quite a lot. That applies to "zeners" having a Vz of
><5.6V. Devices having a Vz of >6.2V aren't really "zeners," they're
>low-voltage avalanche diodes selected for specific avalanche voltages.
Good points
>Those also have a TCBV, and it's just the opposite of zeners. Around 5.6V,
>the TCZ or TCBV is usually zero, so this is a very good voltage to use, when
>possible. It's about as stable as a zener gets.
Would the case temp of said zener be nmt 25ºC at 4.48W diss. in July?
>
Cheers, Steve
- R. L. Measures, a.k.a. Rich..., 805.386.3734,AG6K,
www.vcnet.com/measures.
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