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From: email@example.com (Tom Bruhns)
Subject: Re: 1.6V zener diodes?
Date: 18 Oct 2002 13:06:18 -0700
References: <firstname.lastname@example.org> <email@example.com> <firstname.lastname@example.org>
NNTP-Posting-Date: 18 Oct 2002 20:06:18 GMT
email@example.com (carltons) wrote in message news:...
> In article , Winfield Hill
> > 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.
> 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
So...the really good references (short of NIST Josephson junctions ;-)
appear, still, to use a zener at their heart.
But what I was thinking of was, just as you say, those little two-lead
(or SOT-23) parts that just have a single junction in there doing the
work. Given that I'm dealing with volumes that don't warrant a custom
IC design, how else can I very simply get less than 1uA between two
nodes up to within a volt or closer of the knee (at 10 volts), and
with not very many millivolts change have the current go from the uA
region to the mA region? The ability to do that with such a simple
part is sometimes quite valuable. In the application I'm thinking of,
I don't have to introduce any power supplies to accomplish the task.
Both nodes can be high impedance and there's no problem. When below
its knee voltage, it's pretty darned quiet. Unlike with the 6AL5, I
don't have to provide any heater current... I'd be much less likely
to use zeners in low-voltage circuits, but they're quite handy,
sometimes, in things that run from +/-15V or more.
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