[sdiy] Clipping Amplifier questions...

[René Schmitz]

Hi all,

Czech Martin wrote:
> Note that real zener (avalance) action will typically
> set in about 6-8 V, depending on doping profiles.
> There is a limit on how much doping can be made, so
> the avalanche can not be made to start much lower.

AFAIK "zeners" do employ two distinct mechanisms, zener effect and 
avalanche effect. The avalanche being more prominent than the zehner 
effect for higher voltages.

> "Zener" diodes with less voltage are often normal diode strings
> in forward conduction. They show no sharp zener clamping
> slope, but a soft characteristic which will sometimes
> make correct circuit function impossible.

Arround 5-6V the temperature effects of both mechanisms are about equal 
(but with opposite signs). (So these are the most stable.) One could 
call them avalanche diodes above 6, and zehners below 6V. Until you 
reach the lower end of the zener effect. I think the lowest real zehner 
you can buy is 3.6V or so. Below that -> diodes, as you say.

Cheers,
  René

-- 
uzs159 at uni-bonn.de
http://www.uni-bonn.de/~uzs159