[Amps] Zener Screen Regulators

[TexasRF at aol.com]

Hi Bill. the self destruct action is a dissipation issue. A typical 1000v  
3A diode can handle about 2A on a continuous basis and that comes out to 
about  1.5 watts (.7V X 2A).
 
Many of the 1N5408 diodes tested showed avalanche action at about 1400v.  
Staying within the 1.5 watt figure, that allows only 1.5 / 1400 = 1.07 
milliamps  current flow. One would expect long term survival at that  
voltage/current/wattage. 
 
A 12 v zener might have a 25 watt rating and that would allow 2.08 amps  
that needs derating to about 1A for long term survival.
 
I am not sure what application a 1.5W 1400v zener would be needed for but  
the part is readily available.
 
73,
Gerald K5GW
 
 
 
 
 
In a message dated 9/6/2012 10:09:12 A.M. Central Daylight Time,  
dezrat1242 at yahoo.com writes:

ORIGINAL  MESSAGE: 
vOn Thu, 06 Sep 2012 11:55:28 +0100, David wrote:

>To  add a spanner into the works regarding the direction of current, I 
don't know  
>why these things are call zener diodes, since all the high voltage  ones 
work on 
>avalanche breakdown.
>
>Dave,  G8WRB

REPLY: 
Zener diodes are different from regular diodes because  they are designed 
to pass
current in the reverse direction and survive. All  silicon diodes have a 
zener
point where they begin reverse conduction, but  unless they are specifically
designed for it, most of them will immediately  self-destruct. 

More info:   http://en.wikipedia.org/wiki/Zener_diode

73, Bill  W6WRT
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