1% zener diodes?

[James Arthur]

]

In practice, +30v and two cascaded zener shunt regulators did pretty
well, but you could also do something like this:
(view in Courier font)

.-----------------------------.
| |
| |
.-. |
| | R1 |
| | (trim for |\ |
'-' desired iz) | \ |
| | \ |
+----------------|+ \ |
| | \-------o-------> Vout
| | / |
,---' .--------|- / |
/ \ ZD1 | | / |
--- | | / .-.
| | |/ | | R2 (trim for
| | | | desired Vout)
=== | '-'
GND | |
'---------------------+
|
.-.
| |R3
| |
'-'
|
|
===
GND

I think the above circuit's even self-starting if you choose an op-amp
with sufficiently high bias currents and use low-enough valued
feedback resistors. Otherwise, throw on a starter.

Cheers,
James Arthur

741 (and some brands of 709) OpAmp's will self-start in this
configuration. I built hybrid circuits using this circuit between
1970 and 1973 at Dickson Electronics. Other OpAmp's may NOT
necessarily self-start. So I handled that problem with a
resistor/disconnect-diode scheme.

...Jim Thompson

Well, I was thinking of the LM324, what with its PNP inputs, not to
mention fabulous precision & noise ;-), but there are others...

Oh, sheesh ... okay, you've shamed me into it:

"Bootstrapped reference with startup"

Vcc
-+-
| .-----------------------------.
| | |
| | |
.-. .-. |
| |R4 | | R1 |
| | | | (trim for |\ |
'-' '-' desired iz) | \ |
| D1 | | \ |
V1-> +--|>|--o----------------|+ \ |
[*] | | | \-------o-------> Vout
.-. | | / |
| |R5 ,---' .--------|- / |
| | / \ ZD1 | | / |
| | --- | | / .-.
'-' | | |/ | | R2 (trim for
| | | | | desired Vout)
=== === | '-'
GND GND | |
'---------------------+
|
.-.
[*] V1 < V(ZD1) | |R3
| |
'-'
|
|
===
GND

Cheers,
James Arthur

 

[Jim Thompson]

]

In practice, +30v and two cascaded zener shunt regulators did pretty
well, but you could also do something like this:
(view in Courier font)

.-----------------------------.
| |
| |
.-. |
| | R1 |
| | (trim for |\ |
'-' desired iz) | \ |
| | \ |
+----------------|+ \ |
| | \-------o-------> Vout
| | / |
,---' .--------|- / |
/ \ ZD1 | | / |
--- | | / .-.
| | |/ | | R2 (trim for
| | | | desired Vout)
=== | '-'
GND | |
'---------------------+
|
.-.
| |R3
| |
'-'
|
|
===
GND

I think the above circuit's even self-starting if you choose an op-amp
with sufficiently high bias currents and use low-enough valued
feedback resistors. Otherwise, throw on a starter.

Cheers,
James Arthur

741 (and some brands of 709) OpAmp's will self-start in this
configuration. I built hybrid circuits using this circuit between
1970 and 1973 at Dickson Electronics. Other OpAmp's may NOT
necessarily self-start. So I handled that problem with a
resistor/disconnect-diode scheme.

...Jim Thompson

Well, I was thinking of the LM324, what with its PNP inputs, not to
mention fabulous precision & noise ;-), but there are others...

Oh, sheesh ... okay, you've shamed me into it:

"Bootstrapped reference with startup"

Vcc
-+-
| .-----------------------------.
| | |
| | |
.-. .-. |
| |R4 | | R1 |
| | | | (trim for |\ |
'-' '-' desired iz) | \ |
| D1 | | \ |
V1-> +--|>|--o----------------|+ \ |
[*] | | | \-------o-------> Vout
.-. | | / |
| |R5 ,---' .--------|- / |
| | / \ ZD1 | | / |
| | --- | | / .-.
'-' | | |/ | | R2 (trim for
| | | | | desired Vout)
=== === | '-'
GND GND | |
'---------------------+
|
.-.
[*] V1 < V(ZD1) | |R3
| |
'-'
|
|
===
GND

Cheers,
James Arthur

There you go!

...Jim Thompson

 

[Fred_Bartoli]

James Arthur a écrit :

]

In practice, +30v and two cascaded zener shunt regulators did pretty
well, but you could also do something like this:
(view in Courier font)
.-----------------------------.
| |
| |
.-. |
| | R1 |
| | (trim for |\ |
'-' desired iz) | \ |
| | \ |
+----------------|+ \ |
| | \-------o-------> Vout
| | / |
,---' .--------|- / |
/ \ ZD1 | | / |
--- | | / .-.
| | |/ | | R2 (trim for
| | | | desired Vout)
=== | '-'
GND | |
'---------------------+
|
.-.
| |R3
| |
'-'
|
|
===
GND
I think the above circuit's even self-starting if you choose an op-amp
with sufficiently high bias currents and use low-enough valued
feedback resistors. Otherwise, throw on a starter.
Cheers,
James Arthur

741 (and some brands of 709) OpAmp's will self-start in this
configuration. I built hybrid circuits using this circuit between
1970 and 1973 at Dickson Electronics. Other OpAmp's may NOT
necessarily self-start. So I handled that problem with a
resistor/disconnect-diode scheme.

...Jim Thompson

Well, I was thinking of the LM324, what with its PNP inputs, not to
mention fabulous precision & noise ;-), but there are others...

Oh, sheesh ... okay, you've shamed me into it:

"Bootstrapped reference with startup"

Vcc
-+-
| .-----------------------------.
| | |
| | |
.-. .-. |
| |R4 | | R1 |
| | | | (trim for |\ |
'-' '-' desired iz) | \ |
| D1 | | \ |
V1-> +--|>|--o----------------|+ \ |
[*] | | | \-------o-------> Vout
.-. | | / |
| |R5 ,---' .--------|- / |
| | / \ ZD1 | | / |
| | --- | | / .-.
'-' | | |/ | | R2 (trim for
| | | | | desired Vout)
=== === | '-'
GND GND | |
'---------------------+
|
.-.
[*] V1 < V(ZD1) | |R3
| |
'-'
|
|
===
GND

Cheers,
James Arthur

You just need one resistor from the pos. rail to the output (it'd take a
pretty crappy offset to be greater than about half the output Vcesat).
With this you can even balance the divider's current and avoid the opamp
some dissipation.

 

[Phil Hobbs]

The LM399 is another. Ovenized so you can get +/-1ppm/K guaranteed
(0.3ppm typ) with 7uV noise typical (vs. 200 times as much for an
LM317).

Quite a bit noisier though, just due to the high operating temperature.

I remember that.. sends shivers up my spine. Integrating soft errors.
Yuk.

Germ of a nice idea though...it ought to be possible to make a hybrid
reference, e.g. with a high power, quiet reference that gets fired up
periodically to adjust the voltage on a hold cap. You could even
correct for the kT/C noise, and all at really low power.

Cheers,

Phil Hobbs

 

[James Arthur]

James Arthur a écrit :

On Wed, 25 Jul 2007 10:05:03 -0700, James Arthur

[...]

In practice, +30v and two cascaded zener shunt regulators did pretty
well, but you could also do something like this:
(view in Courier font)
.-----------------------------.
| |
| |
.-. |
| | R1 |
| | (trim for |\ |
'-' desired iz) | \ |
| | \ |
+----------------|+ \ |
| | \-------o-------> Vout
| | / |
,---' .--------|- / |
/ \ ZD1 | | / |
--- | | / .-.
| | |/ | | R2 (trim for
| | | | desired Vout)
=== | '-'
GND | |
'---------------------+
|
.-.
| |R3
| |
'-'
|
|
===
GND
I think the above circuit's even self-starting if you choose an op-amp
with sufficiently high bias currents and use low-enough valued
feedback resistors. Otherwise, throw on a starter.
Cheers,
James Arthur
741 (and some brands of 709) OpAmp's will self-start in this
configuration. I built hybrid circuits using this circuit between
1970 and 1973 at Dickson Electronics. Other OpAmp's may NOT
necessarily self-start. So I handled that problem with a
resistor/disconnect-diode scheme.
...Jim Thompson

Well, I was thinking of the LM324, what with its PNP inputs, not to
mention fabulous precision & noise ;-), but there are others...

Oh, sheesh ... okay, you've shamed me into it:

"Bootstrapped reference with startup"

Vcc
-+-
| .-----------------------------.
| | |
| | |
.-. .-. |
| |R4 | | R1 |
| | | | (trim for |\ |
'-' '-' desired iz) | \ |
| D1 | | \ |
V1-> +--|>|--o----------------|+ \ |
[*] | | | \-------o-------> Vout
.-. | | / |
| |R5 ,---' .--------|- / |
| | / \ ZD1 | | / |
| | --- | | / .-.
'-' | | |/ | | R2 (trim for
| | | | | desired Vout)
=== === | '-'
GND GND | |
'---------------------+
|
.-.
[*] V1 < V(ZD1) | |R3
| |
'-'
|
|
===
GND

Cheers,
James Arthur

You just need one resistor from the pos. rail to the output (it'd take a
pretty crappy offset to be greater than about half the output Vcesat).
With this you can even balance the divider's current and avoid the opamp
some dissipation.

The R4-5 divider needn't source much current--just enough to overwhelm
the op amp's bias current, whereas the one-resistor pullup needs to
provide a little more juice to dominate the op-amp's output stage, I
suspect, depending on the op amp... but I like it.

Simple, clever. Nice touch.

Cheers,
James Arthur

 

[Joerg]

Ahh, thanks. Still, even a 0.5mA change in i(z) only results in a 5mV
initial error; any affect on drift would be a 2nd order affair from
there. So, the accuracy isn't fantastic, but the precision and drift
are really pretty good.

Until you get the next production lot and the guy from final QC comes
down the hallway, flailing and hollering and all that.

Plus Digikey doesn't have any. Not a good sign ....

[...]

 

[Michael A. Terrell]

A linear supply with lots of expensive stuff connected and no crowbar is
like crossing a canyon via rope with a safety hook. You still get there,
usually ....

A sergeant at basic training accidentally did just that, forgot to
engage his safety hook. He did reach the other side but upon discovering
his mistake he nearly fainted and was literally shaking in his boots.

He was probably thinking about all the paperwork he'd have to do if
he fell, and lived. Destruction of government property creates lots of
extra work.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

 

[James Arthur]

Until you get the next production lot and the guy from final QC comes
down the hallway, flailing and hollering and all that.

If you need super performance you gotta tune each one Joerg, of
course. Or buy an IC with a buried zener in it.

Plus Digikey doesn't have any. Not a good sign ....

[...]

Digikey?

Grins,
James Arthur

 

[Joerg]

If you need super performance you gotta tune each one Joerg, of
course. Or buy an IC with a buried zener in it.

I'd vote for the IC then ;-)

Plus Digikey doesn't have any. Not a good sign ....

[...]

Digikey?

Yeah, my house rule here is that when Digikey doesn't carry something or
is constantly out of stock on it then it's a boutique part. And boutique
parts usually turn into sleepless nights, overtime, cancelled vacation
trips and all that.

))

 

[Winfield]

My B-E junctions were integrated, 1mil X 1.5mil at that old
time when device dimensions were huge ;-) Ran it at 100uA.

Fine, if you're an IC designer and can control the properties
of your 100uA device. My point was that 1% zener diodes are
basically a waste, unless their 1% voltage and tempco specs
are specified at a sensible current, rather than the usual
20mA. I think that's why they didn't succeed as a product.
On the other hand, voltage-reference ICs with 1% or better-
specs certainly did succeed. At least in my designs. And,
they ran at sensible currents.

If you used a reverse-BE junction and well-controlled its
characteristics, that's great, because the tempco could
have been lower than the usual Vbe-reference device. One
of the things I liked about the venerable 723 regulator IC
was its nice quiet zener diode.

 

[Joerg]

Fine, if you're an IC designer and can control the properties
of your 100uA device. My point was that 1% zener diodes are
basically a waste, unless their 1% voltage and tempco specs
are specified at a sensible current, rather than the usual
20mA. I think that's why they didn't succeed as a product.
On the other hand, voltage-reference ICs with 1% or better-
specs certainly did succeed. At least in my designs. And,
they ran at sensible currents.

Exactly. Plus most of the "low current zeners" are just the same old
soup, regular zeners measured in the knee. I had lengthy discussions
with mfgs about delivering real low current zeners after a client had a
major line stop situation where a low current zener drifted out of spec
after the umpteenth reel. The result? More of those "measured in the
knee" varieties. So I designed in the TLV431. No more zeners there.
Meaning they lost a business they could have had.

Why don't they make smaller geometry zeners? It can't be rocket science
and the profits from each wafer should greatly increase.

 

[Rich Grise]

Yeah, my house rule here is that when Digikey doesn't carry something or
is constantly out of stock on it then it's a boutique part. And boutique
parts usually turn into sleepless nights, overtime, cancelled vacation
trips and all that.

Seems like an awful lot of paperwork for a thing where you could have just
said, "No, thanks." ;-)

Cheers!
Rich

 

[[email protected]]

Where'd you see the +/- 0.01mA? I couldn't find it.

It is at the top of the second page of the data sheet.

 

[[email protected]]

I once read somewhere that you could put an ordinary forward-biased
silicon diode in series with a zener and their tempcos would tend to
cancel out, albeit they didn't say how well.

Someone published a short paper in the (British) Journal of Scientific
Instruments some forty years ago on using the forward-biased collector
base diode of a 2N2639 gold-doped switching transistor

http://www.ortodoxism.ro/datasheets/fairchild/MMBT2369A.pdf

to compensate the the tempeature coefficient of the reversed biased
base-emitter diode.

Because both diodes were at the same place in the same package, the
temperature compensation could be pretty good, and the paper went on
to tell you how to tune the current through the part (at around 2mA)
to minimise the temperature coefficient of the part as a whole - you
produced a temperature excursion in the part by prodding it with a hot
soldering iron and monitored the voltage drop across the part with a
six-digit digital voltmeter ...

A really neat trick, but one that I've never tried to use.