NNTP-Posting-Date: Sun, 12 Jan 2003 17:36:50 -0600
From: Barry Lennox
Subject: Re: In search of special temperature sensitive Zener
Date: Mon, 13 Jan 2003 12:38:55 +1300
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On Sat, 11 Jan 2003 11:01:58 -0800, mike wrote:
Well, you may have to fool around a bit! It's been a long time ago,
but I'll try to remember some work I did.
Low voltage zeners have a negative tempco, while above about 4-5 volts
it changes to positive. The exact tempco can be set by changing the
bias current through the zener, can you do that? The amount of tempco
change by bias adjustment can vary from device to device, but the
effect is *much* more pronouced up near 4-5 volts. Maybe you could
tweak the tempco to what's required, then divide down the voltage to
the desired 2.8 volts, Could become a long interactive project this.
Below 6 volts, individual zeners can vary in their tempco, and some
drift much more than others, you may have to get a pile of them, and
select on test.
The tempco is inherent in the zener mechanism, and I suspect you
cannot find different voltage zeners with the same tempco, subject to
the tweaking and selecting-on-test tricks described above. The ones I
spent hours fooling with was the Motorola 1N5226 to 1N5230 family.
Best of luck,
>> I am trying to replace a temperature sensor in an air conditioner unit (as
>> part of a custom installation) to decrease the minimum temperature that can
>> be set.
>> The existing information I have is :-
>> - The zener diode looks like a 1/8 w dark yellow axial with clear band in
>> - The operating voltage is about 3v.
>> - The voltage decreases at about 40mV/C
>> - Using a diode checker (with unit powered off) showed 0.6 v drop in one
>> direction only, high resistance is other direction.
>> I need to determine the type of diode and get a replacement that has
>> slightly lower nonimal voltage (about 2.8v at room temp) but with the same
>> temp coeff.
>> If anyone can help at all I would be very grateful.