[Amps] Zener Screen Regulators

[Bill Fuqua]

An interesting note about current flow.
I am a professional engineer and we have to have Continuing Education 
Credits to renew license every two years.
There a number of places that offer these courses for a price on line. Some 
use public domain materials and offer a
little quiz afterwards and send you a certificate. Some use old navy 
training books. Naturally, those use electron
current flow and all the engineering materials use conventional current 
flow (positive to negative).
A bit confusing for a young engineer but not for an old timer who has had 
to deal with both.
73
Bill wa4lav



At 07:37 PM 9/3/2012 -0700, Bill, W6WRT wrote:
>ORIGINAL MESSAGE:
>On Mon, 3 Sep 2012 11:15:20 -0600, you wrote:
>
> >
> >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
>
>REPLY:
>I think we agree on everything but semantics. I often get tangled up with the
>"current flows from positive to negative" boys over the terms source and 
>sink.
>
>Benjamin Franklin got it wrong and the IEEE and others have been perpetuating
>the error ever since. I usually ask the positive to negative boys why a 
>tube has
>to have a heated filament or cathode in order to "receive" current flow 
>from the
>anode. Still waiting for an answer.
>
>73, Bill W6WRT
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