[Amps] Bias Zener Diodes In Parallel ?

[dan hearn]

Unfortunately the branch which has the lower total zener voltage will
take most of the current so that is not a good idea. Fortunately, there
is a good simple solution to your problem. A power transistor with a
single zener and a resistor will make a good bias source. One I have
used with an 8877 consists of a 2n3055 with an 8.2 volt zener from
collector to base and a 47 ohm 2w resistor from base to emitter. The
zener cathode goes to the collector. The emitter goes to gnd and the
collector to the amp cathode. I have seen this design in several
published amp circuits. Sometimes a power resistor 5K 20w is shunted
across the transistor collector to base. I think this may be to protect
the tube in case of failure of the bias circuit. 
73, Dan, N5AR

Douglas R Snowden wrote:
> 
> 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?
> 
> Doug, N4IJ
> 
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