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From: email@example.com (carltons)
Subject: Re: 1.6V zener diodes?
References: <firstname.lastname@example.org> <email@example.com> <10Pq9.508$Vv3.firstname.lastname@example.org> <email@example.com> <firstname.lastname@example.org>
User-Agent: NewsWatcher-X 2.2.3b2
NNTP-Posting-Date: Fri, 18 Oct 2002 00:08:53 GMT
Date: Fri, 18 Oct 2002 00:08:53 GMT
In article , Winfield Hill
> Steve wrote...
> > Tom Bruhns wrote:
> >> email@example.com (carltons) wrote
> >> ...
> >>> All of the suggestions other than the use of a zener of any sort sound
> >>> good to me. A Zener is okay for ESD protection as a last resort, but
> >>> other than that, it has gone the way of the 6AL5 tube diode. ...
> >> I'd say you're under-rating the zener's usefulness for things other
> >> than ESD protection and noise generation (and perhaps even over-rating
> >> it for those). There are some things they do very well for low cost
> >> which would be quite difficult to do other ways. ;-) (Though we
> >> haven't seen any confirmation from the OP, his application is likely
> >> not one of the good ones, of course!)
> > Coming from the world of low voltage portable equipment, I'm not a big fan
> > of shunt regulation. There are also many ways to get better performance
> > these days. Why use a zener? When I was doing ic design, suggesting a
> > zener would have gotten you walked out the door immediately. Also, zeners
> > have really lousy junction capacitance which made them perfect for esd on
> > portable radios as they didn't rectify the rf past about 1 MHz. All our
> > radios were 30 MHz and above.
> You're right Steve, the use of zener (field-emission breakdown) technology
> is not recommended for low-voltage design. But don't trash zener diodes
> for all the "high-voltage" (over 5 volts) folks. High-voltage zeners
> (avalanche technology) work very well in a wide variety of tasks, often
> much better or at least more efficiently than the alternates. And well-
> designed zener diodes in the 5.6 to 6.8-volt region (field-emission plus
> avalanche) are very excellent performers indeed, featuring low noise,
> low-resistance, and nearly zero temperature coefficient. Nice stuff.
> You mention IC designers eschewing zeners? Low-voltage ICs often have an
> internal zener across the supply to make sure they stay at low voltages.
> :-) Certainly zeners are very common in ICs that operate from 8V or more.
> They're often seen in current-source bias-startup circuitry, or to limit
> the voltage at some point. Finally, don't forget that the top-performing
> voltage-reference ICs employ buried-zener technology, because it's quieter
> than the competing cheap band-gap stuff. Zener voltage-reference ICs even
> outperform Analog Devices' amazing new proprietary XFET technology. E.g.,
> compare NSC's LM399 or LTC's LT1000 and LT1021 with Analog's ADR421.
> LTZ1000A LM399A LT1021C ADR421BR LT1019A
> zener zener zener XFET bandgap
> ------ ------- ------- ------- -------
> accuracy 4% 2% 0.05% 0.04% 0.05% max
> tempco 0.05ppm 0.5ppm 5ppm 3ppm 5ppm/C max
> noise 0.17ppm - 0.6ppm 0.7ppm 2.5ppm p-p typ, 0.1 to 10Hz
> drift 0.3ppm 20ppm 15ppm 50ppm est 50ppm per 1000 hours
> That old chestnut, "The right part for the right task," insures that zener
> diodes will continue to have an important role in electronics. Some may
> think that in the future few ICs will operate above 1.8 or 2.7 volts, etc.,
> but I seriously doubt it. :-)
> - Win
I appreciate what you're trying to say, however most of the "Zeners" above
have a lot of IC circuitry around them and loads of gain and feedback
along with heaters, etc to make them acceptable. My term "Zener" is a
single diode with nothing in the package but the diode and its wire
bonds. The LTZ1000 and LM399 both have great TC, but at the expense ($
and Isupply) of on-board heaters. The zeners that I refer to a have
designations such as 1Nxxx etc. and they don't have schematics on their
spec sheet to show what's inside. You already know that there is just a
diode with two leads and some plastic on the outside.
Good trick is to get the same specs for a 1.6v "zener" with a supply of
2.0v (end of life for two "AA" or "AAA" cells) at less than 1 mA of total
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