making up zener diodes

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if a 75volt zener connect in series with
a 15 volt zener would it work as a
100 volt zener?

thankyou
zack



Re: making up zener diodes


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75+1590%

Re: making up zener diodes



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ok
will it work?



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It would work as a 90 volt zener, not as a 100 volt one.

--
Dyna

All rights reserved. All wrongs avenged.



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thankyou
for the info

zack



Re: making up zener diodes



"`ZACK`"

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** Aside from your math error, the basic idea is 100% OK.

Strings of zeners wired in series up to 50 are seen in commercial devices.

It works.



.....  Phil



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Will give 90v not 100v   (75v+15v90%v)

No problems with series zeners though as long as they are the right
wattage.
I used 3x 30v in series once to make a 90v zener. No problem.

Re: making up zener diodes



"kreed"
 "`ZACK`"
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** Quad used no less than 32 x 220 volt zeners wired in series to make a
voltage limiter for their ESL63 speaker.

Yep  -   it limited at  +/-  7000 volts  !!!!

See list of schems in the middle of this page:

http://www.dadaelectronics.eu/downloads


.....   Phil



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Very impressive.  Not that I can think of another practical way to do
it.

Another "series zener" application I was told of years back , is in
very long distance communication cables. (probably also undersea
submarine cables).  In the example I was told of (a 300km land based
cable) in order to power all of the the many inline booster/repeater
boxes they had a single supply cable in the line that was connected to
+750vdc at one end and -750vdc at the other end. All the "booster"
boxes in the line would wired in series along this high voltage line
that was at 1500v potential end to end.
The earth would be the return.

At each box, they would put a zener diode in series with this high
voltage line and draw the unit's supply rail voltage from across this
zener.  For example, if each box required 50v, and there were 30
boxes , there would be a total of 30x 50v zeners in series in the
1500v line.

(I cant remember exactly how many boxes were used, or the supply
voltage for each - just used these figures as an example)

Even with fibre optic cables being used these days, they more than
likely still need to be boosted every so many KM over long runs ? so
this method no doubt would still be used for powering boosters.


If series zeners are reliable enough for extremely critical
applications like undersea cables, then they are reliable enough for
pretty much anything as far as I'm concerned.




Re: making up zener diodes


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Providing the tolerance is OK (5% per diode) and you are drawing the
minimum current to get the zener effect.

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