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[Amps] Bias Zener Diodes In Parallel ?

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Subject: [Amps] Bias Zener Diodes In Parallel ?
From: W8JI@contesting.com (Tom Rauch)
Date: Wed, 17 Jul 2002 10:30:19 -0400
> 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?

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.

You know diodes can run pretty hot and remain safe.

You could try to parallel another totally separate series string. ESR 
probably would be high enough that you may not need to equalize the 
strings with external resistors You'd have to test that, and make 
sure the strings were substantially equal in voltage.

I'd probably just use a couple power transistors as a wrap around 
device to boost current, unless you wanted to use a diode reference 
and build a two- or three-transistor adjustable regulator.73, Tom 
W8JI
W8JI@contesting.com 


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