[Amps] Zener Screen Regulators

[Jim Garland]

> If you have a simple zener (or two) you don't need a separate bleeder. The
> zener(s) will supply the negative current.
> 
> Remember - When the zener(s)is supplying negative current it is also
supplying
> positive current through the feed resistor, so be sure the zener(s) is
rated to
> handle both the positive idle current and any possible negative current at
the
> same time.
> 
> 73, Bill W6WRT

Bill,
I'm not sure what you mean by a zener diode "supplying negative current."  A
zener diode doesn't supply any current at all, positive or negative. It
sinks current while maintaining a constant voltage. If, for example, 100mA
is supplied by the "feed resistor" and there is -20mA of negative screen
current, the the zener will sink 120 mA.  If there is +20mA of positive
screen current, the zener will sink 80mA. If the screen current rises to
+100mA, then the zener will drop out of regulation and the screen voltage
will drop. That said, I agree that no separate bleeder is required with a
zener diode regulator. In effect, the zener acts as the bleeder.
73,
Jiim W8ZR