Zeners in Series

[Cursitor Doom]

Whilst mere hobbyists like myself can easily get away with making up a
desired zener value from putting two smaller value ones in series to add
together their rated voltages, can such a dodge be employed by
professional designers without losing face? I mean, in the case where
there is no commercially available zener with precisely the desired
breakdown voltage? Would a pro designer be open to ridicule and risking
his rep by pulling such a stunt?



--
This message may be freely reproduced without limit or charge only via
the Usenet protocol. Reproduction in whole or part through other
protocols, whether for profit or not, is conditional upon a charge of
GBP10.00 per reproduction. Publication in this manner via non-Usenet
protocols constitutes acceptance of this condition.

 

[Tom Gardner]

On 09/11/19 21:42, Cursitor Doom wrote:

Whilst mere hobbyists like myself can easily get away with making up a
desired zener value from putting two smaller value ones in series to add
together their rated voltages, can such a dodge be employed by
professional designers without losing face? I mean, in the case where
there is no commercially available zener with precisely the desired
breakdown voltage? Would a pro designer be open to ridicule and risking
his rep by pulling such a stunt?

My question would be "what is the problem to which you think
that is a good solution?".

Only then I would consider whether that is an adequate
thing to do.

If nothing else, you should assure yourself that the
voltage will be sufficiently accurate and stable as
temperature and current vary.

 

[Phil Allison]

Cursitor Doom wrote:

---------------------

Whilst mere hobbyists like myself can easily get away with making up a
desired zener value from putting two smaller value ones in series to add
together their rated voltages, can such a dodge be employed by
professional designers without losing face?

** Yep,

engineering = making what you need with what you have got.

I mean, in the case where
there is no commercially available zener with precisely the desired
breakdown voltage? Would a pro designer be open to ridicule and risking
his rep by pulling such a stunt?

** I have used series strings of 8 or more 12V 3W zeners to get high voltage and high power dissipation - all mounted on a tag strip.

Fitting them in series with the screens supply of output tubes to stop overheating damage when clipping.

100V, 20W zeners need an isolated heatsink and are not cheap.

You do what you need to do.

Only wankers worry about how it looks.



..... Phil

 

On Saturday, November 9, 2019 at 4:42:43 PM UTC-5, Cursitor Doom wrote:

Whilst mere hobbyists like myself can easily get away with making up a
desired zener value from putting two smaller value ones in series to add
together their rated voltages, can such a dodge be employed by
professional designers without losing face? I mean, in the case where
there is no commercially available zener with precisely the desired
breakdown voltage? Would a pro designer be open to ridicule and risking
his rep by pulling such a stunt?



--
This message may be freely reproduced without limit or charge only via
the Usenet protocol. Reproduction in whole or part through other
protocols, whether for profit or not, is conditional upon a charge of
GBP10.00 per reproduction. Publication in this manner via non-Usenet
protocols constitutes acceptance of this condition.

But, is it really good practice to use only a stack of zeners? Should there not be a hi impedance bleeder path in parallel to each of the diode(s) stack so they all start to conduct and zener properly. Phil I'm surprised you did not mention this.

 

Transorbs are two way senders and we employ two in series based upon power considerations

 

[Robert Baer]

Cursitor Doom wrote:

Whilst mere hobbyists like myself can easily get away with making up a
desired zener value from putting two smaller value ones in series to add
together their rated voltages, can such a dodge be employed by
professional designers without losing face? I mean, in the case where
there is no commercially available zener with precisely the desired
breakdown voltage? Would a pro designer be open to ridicule and risking
his rep by pulling such a stunt?

Oil 4 LessÂŽ LLC makes their low noise CodatronÂŽ high voltage zener,
capable of operation to 204 degrees Centigrade / 400 degrees Fahrenheit
and can program them from 50V to 2500V in 50V steps.
A ten volt step version is in prototype now.
Been sold for over ten years, and in many countries.

What voltage and quantities are you looking for?

 

[Phil Allison]

alan.ye...@gmail.com wrote:
-------------------------------------

But, is it really good practice to use only a stack of zeners?
Should there not be a hi impedance bleeder path in parallel to
each of the diode(s) stack so they all start to conduct and zener
properly.
Phil I'm surprised you did not mention this.

** Surely you jest ?

Might as well fit bleeders in parallel with cells in a battery.

Make the bastards share the damn current ....



.... Phil

 

[Tom Del Rosso]

Cursitor Doom wrote:

Whilst mere hobbyists like myself can easily get away with making up a
desired zener value from putting two smaller value ones in series to
add together their rated voltages, can such a dodge be employed by
professional designers without losing face? I mean, in the case where
there is no commercially available zener with precisely the desired
breakdown voltage? Would a pro designer be open to ridicule and
risking his rep by pulling such a stunt?

Win and others here have noted that zeners above 7V produce much more
noise.

You were in this thread too.


Saturday, May 27, 2017 9:15 PM
Subject: Combating Zener Jitter


Jim Thompson wrote:

AKA Flicker Noise

Yup, pink noise. No jittering/jitterbugging involved.

Winfield Hill wrote:

Actually, I'd say you're wrong. The zener noise that we
see in avalanche mode (greater then 7 volts or so) is due
to step-wise "microplasma" ns-scale changes in current.
A decade or so ago we fully discussed it here on s.e.d.,
complete with measurements, waveforms, detailed physics
paper references and the works. Nailed it down. As it
happens, the jitterbug analogy isn't so far off.

This avalanche jitterbug noise source is not available
in the low-voltage field emission zener operating mode,
so using two sub-6-volt zeners in series in place of a
higher-voltage zener, or any of many other good schemes
would indeed be a good idea.

Tom Del Rosso wrote...

Is the low-voltage noise less than half, so it
won't add up to more?

Winfield Hill wrote:

> Yes, it's a tiny fraction. Try it.

 

[Phil Allison]

Bill Slowman wrote:

------------------

But, is it really good practice to use only a stack of zeners? Should there not be a hi impedance bleeder path in parallel to each of the diode(s) stack so they all start to conduct and zener properly. Phil I'm surprised you did not mention this.

About the only problem with using a stack of zeners is running them at high enough current to prevent the avalanche process from turning itself off.

** My one problem was making sure 3W zeners had enough heat sinking so they did not de-solder themselves and fall right off the tag strip.

Simple fix was to use more, lover voltage types.

Damn those heavy metal guitarists !!


..... Phil

 

[Bill Sloman]

On Sunday, November 10, 2019 at 10:40:29 AM UTC+11, alan.ye...@gmail.com wrote:

On Saturday, November 9, 2019 at 4:42:43 PM UTC-5, Cursitor Doom wrote:
Whilst mere hobbyists like myself can easily get away with making up a
desired zener value from putting two smaller value ones in series to add
together their rated voltages, can such a dodge be employed by
professional designers without losing face? I mean, in the case where
there is no commercially available zener with precisely the desired
breakdown voltage? Would a pro designer be open to ridicule and risking
his rep by pulling such a stunt?

But, is it really good practice to use only a stack of zeners? Should there not be a hi impedance bleeder path in parallel to each of the diode(s) stack so they all start to conduct and zener properly. Phil I'm surprised you did not mention this.

About the only problem with using a stack of zeners is running them at high enough current to prevent the avalanche process from turning itself off.

The isn't a problem with low voltage zener diodes which rely on the Zener mechanism, but anything above about six volts is an avalanche diode.

The volume in which the avalanche multiplication occurs is tiny, and if you operate at a current low enough that there's only one electron going through that region at a time there's a risk that it will get through without generating another pair of charge carriers, and the voltage across the diode will rise rapidly until another charge carrier gets generated by thermal noise.

People exploit this effect by running zener diodes at low current to serve as noise sources.

https://en.wikipedia.org/wiki/Noise_generator

If you are very unlucky, a zener diode operating at low current can look as if it is oscillating at a few hundred MHz. We had a thread about this here many years ago.

--
Bill Sloman, Sydney

 

[Bill Sloman]

On Sunday, November 10, 2019 at 1:23:56 PM UTC+11, Phil Allison wrote:

Bill Slowman wrote:

------------------


But, is it really good practice to use only a stack of zeners? Should there not be a hi impedance bleeder path in parallel to each of the diode(s) stack so they all start to conduct and zener properly. Phil I'm surprised you did not mention this.

About the only problem with using a stack of zeners is running them at high enough current to prevent the avalanche process from turning itself off.

** My one problem was making sure 3W zeners had enough heat sinking so they did not de-solder themselves and fall right off the tag strip.

That does involve working out the power being dissipated in each zener.

The data sheets mostly have thermal derating curves, which indirectly tells you how warm the zener gets at a given power dissipation.

Covering problems like this is the boring but unavoidable part of circuit design.

Simple fix was to use more, lover voltage types.

Damn those heavy metal guitarists !!

You need a theologian for that. I could put you in contact with at least one, but Methodists don't go in for applied theology.

--
Bill Sloman, Sydney

 

On Sat, 9 Nov 2019 21:42:38 -0000 (UTC), Cursitor Doom
<curd@notformail.com> wrote:

Whilst mere hobbyists like myself can easily get away with making up a
desired zener value from putting two smaller value ones in series to add
together their rated voltages, can such a dodge be employed by
professional designers without losing face? I mean, in the case where
there is no commercially available zener with precisely the desired
breakdown voltage? Would a pro designer be open to ridicule and risking
his rep by pulling such a stunt?

It's perfectly fine. Adding a new part to the stockroom is a big deal,
only worth it if you expect to need a lot of them. Two zeners in
series may be good economics. It spreads the power dissipation, too.

I sometimes put resistors or caps in series or parallel, to avoid
adding another line to the BOM of a board, even if all the right
values are in stock. Saves loading up a reel on the pick-and-place to
slam down one cheap part.

I even -gasp- sometimes use only half of a dual diode!

But ridicule? Reputation? Who would know?



--

John Larkin Highland Technology, Inc

lunatic fringe electronics

 

On Saturday, 9 November 2019 23:49:32 UTC, Phil Allison wrote:

alan.ye...@gmail.com wrote:

But, is it really good practice to use only a stack of zeners?
Should there not be a hi impedance bleeder path in parallel to
each of the diode(s) stack so they all start to conduct and zener
properly.
Phil I'm surprised you did not mention this.


** Surely you jest ?

Might as well fit bleeders in parallel with cells in a battery.

Make the bastards share the damn current ....



... Phil

maybe he's thinking of neons. Zeners certainly have no use for such things


NT

 

[Bill Sloman]

On Sunday, November 10, 2019 at 1:38:41 PM UTC+11, jla...@highlandsniptechnology.com wrote:

On Sat, 9 Nov 2019 21:42:38 -0000 (UTC), Cursitor Doom
curd@notformail.com> wrote:

Whilst mere hobbyists like myself can easily get away with making up a
desired zener value from putting two smaller value ones in series to add
together their rated voltages, can such a dodge be employed by
professional designers without losing face? I mean, in the case where
there is no commercially available zener with precisely the desired
breakdown voltage? Would a pro designer be open to ridicule and risking
his rep by pulling such a stunt?

It's perfectly fine. Adding a new part to the stockroom is a big deal,
only worth it if you expect to need a lot of them. Two zeners in
series may be good economics. It spreads the power dissipation, too.

I sometimes put resistors or caps in series or parallel, to avoid
adding another line to the BOM of a board, even if all the right
values are in stock. Saves loading up a reel on the pick-and-place to
slam down one cheap part.

I even -gasp- sometimes use only half of a dual diode!

But ridicule? Reputation? Who would know?

John Larkin does expect rather more praise than he deserves, and does seem to be correspondingly sensitive about his reputation.

Ridicule doesn't work on him. He writes it off as an expression of personal animosity and ignores it, which does mean that he posts the same nonsense time after time, which does make him ridiculous, but not in a way that he can detect.

--
Bill Sloman, Sydney

 

[Phil Allison]

Bill Sloman wrote:

--------------------

** My one problem was making sure 3W zeners had enough heat sinking
so they did not de-solder themselves and fall right off the tag strip.

That does involve working out the power being dissipated in each zener.

** This was back in 1981.

I was then working for a Scientologist - Allen Wright.

Long story.

It first of all involved knowing the max possible average current flow into the screens of four EL34s inside Marshall. The answer is about 80 mA with the tubes driven into hard distortion from a sine generator.

I had used 5 x 18V, 5W zeners in series at fist - worked fine on the bench for 15 minutes. Case temp was hot but not sizzling and I knew power zeners were tough buggers.

Only 1.44 watts each dissipation, mounted well spaced on a large sized tag board that soaked up much of the heat. Must be OK.

But with the chassis back in the wood case, no through ventilation whatever, lots of heat dripping from the power tubes, a hot night and with a loony guitarist who did not take a break for hours - one of the solder joints got a few degrees too hot.

Sound stopped, musicians wept.

A change to 7 x 12 volt zeners was the fix.

All came about because tube factories in Europe and the UK closed down, leaving one US plant going - Philips /Sylvania.

They made an odd version of the EL34 /6CA7 tube that hated high screen voltages and would quickly burn out.

My "zener mod" made it possible to use them safely, I know of no other tech who came up with the same or any solution.

The very first customer got to do some Beta testing for me.



...... Phil

 

[Jan Panteltje]

Whilst mere hobbyists like myself can easily get away with making up a
desired zener value from putting two smaller value ones in series to add
together their rated voltages, can such a dodge be employed by
professional designers without losing face? I mean, in the case where
there is no commercially available zener with precisely the desired
breakdown voltage? Would a pro designer be open to ridicule and risking
his rep by pulling such a stunt?

There are programmable zeners, like the TL431 for example.
That said, I have some zener with a red and green LED in series in my PIC programmer....

In the old days temperature compensation and stuff was done by putting things in series.
But I'd use the TL431 for small currents.
I got 50 of those on ebay for 1$84 free shipping in 2015...

 

[Bill Sloman]

On Sunday, November 10, 2019 at 8:49:43 PM UTC+11, upsid...@downunder.com wrote:

On Sat, 9 Nov 2019 21:42:38 -0000 (UTC), Cursitor Doom
curd@notformail.com> wrote:

Whilst mere hobbyists like myself can easily get away with making up a
desired zener value from putting two smaller value ones in series to add
together their rated voltages, can such a dodge be employed by
professional designers without losing face? I mean, in the case where
there is no commercially available zener with precisely the desired
breakdown voltage? Would a pro designer be open to ridicule and risking
his rep by pulling such a stunt?

Zeners around 5 V have nearly zero temperature coefficient, those
above have a positive TC and those below a negative TC. Thus making a
10 V zener from two 5 V zeners would have zero TC. Using less than 4 V
and over 6 V in series may also reduce the TC. Alternative put some
forward biased diode(s) (TC -2.2 mV/K) in series to compensate for the
positive TC of more than 5 V zeners.

1N821 - 1N829 put a 5.6V zener in the same package as the forward biased diode

pdf.datasheetcatalog.com/datasheet/motorola/1N823.pdf

You get a stable 6.2V reference voltage at precisely 7.5mA. How precisely it's worth hitting 7.5mA depends on the price of the diode - the 1N829 sells for quite a bit more than the 1N821.

Alternatively you can buy one of the cheaper parts and find the exact current gives the lowest temperature coefficient, but it requires a fairly expensive test rig to cover the temperature range.

There are integrated circuits around that can do better.

--
Bill Sloman, Sydney

 

[Cursitor Doom]

On Sat, 09 Nov 2019 18:38:31 -0800, jlarkin wrote:

I even -gasp- sometimes use only half of a dual diode!

But ridicule? Reputation? Who would know?

Everyone here, now you've admitted to still using dual diodes!
:-D



--
This message may be freely reproduced without limit or charge only via
the Usenet protocol. Reproduction in whole or part through other
protocols, whether for profit or not, is conditional upon a charge of
GBP10.00 per reproduction. Publication in this manner via non-Usenet
protocols constitutes acceptance of this condition.

 

[Cursitor Doom]

On Sat, 09 Nov 2019 19:43:40 -0500, Tom Del Rosso wrote:

Cursitor Doom wrote:
Whilst mere hobbyists like myself can easily get away with making up a
desired zener value from putting two smaller value ones in series to
add together their rated voltages, can such a dodge be employed by
professional designers without losing face? I mean, in the case where
there is no commercially available zener with precisely the desired
breakdown voltage? Would a pro designer be open to ridicule and risking
his rep by pulling such a stunt?

Win and others here have noted that zeners above 7V produce much more
noise.

You were in this thread too.

Indeed I was. ISTR I started it. But this is a completely different
matter!




--
This message may be freely reproduced without limit or charge only via
the Usenet protocol. Reproduction in whole or part through other
protocols, whether for profit or not, is conditional upon a charge of
GBP10.00 per reproduction. Publication in this manner via non-Usenet
protocols constitutes acceptance of this condition.

 

[Bill Sloman]

On Sunday, November 10, 2019 at 8:49:43 PM UTC+11, upsid...@downunder.com wrote:

On Sat, 9 Nov 2019 21:42:38 -0000 (UTC), Cursitor Doom
curd@notformail.com> wrote:

Whilst mere hobbyists like myself can easily get away with making up a
desired zener value from putting two smaller value ones in series to add
together their rated voltages, can such a dodge be employed by
professional designers without losing face? I mean, in the case where
there is no commercially available zener with precisely the desired
breakdown voltage? Would a pro designer be open to ridicule and risking
his rep by pulling such a stunt?

Zeners around 5 V have nearly zero temperature coefficient, those
above have a positive TC and those below a negative TC. Thus making a
10 V zener from two 5 V zeners would have zero TC. Using less than 4 V
and over 6 V in series may also reduce the TC. Alternative put some
forward biased diode(s) (TC -2.2 mV/K) in series to compensate for the
positive TC of more than 5 V zeners.

1N821 - 1N829 put a 5.6V zener in the same package as the forward biased diode

pdf.datasheetcatalog.com/datasheet/motorola/1N823.pdf

You get a stable 6.2V reference voltage at precisely 7.5mA. How precisely it's worth hitting 7.5mA depends on the price of the diode - the 1N829 sells for quite a bit more than the 1N821.

Alternatively you can buy one of the cheaper parts and find the exact current gives the lowest temperature coefficient, but it requires a fairly expensive test rig to cover the temperature range.

There are integrated circuits around that can do better.

--
Bill Sloman, Sydney