[volt-nuts] Motorola buried zener

Bruce Griffiths bruce.griffiths at xtra.co.nz
Sun Sep 13 01:40:07 UTC 2009

Mike S wrote:
> At 09:03 PM 9/12/2009, Bruce Griffiths wrote...
>> I thought that they were 1N821 series or similar TC compensated discrete
>> zeners ( series stack of a zener chip plus one or more forward biased
>> diodes all in same hermetically sealed package)?
>> IIRC thats what the manual states.
>> I have datasheets for most of the Motorola TC zeners if thats what
>> you need.
> No, not the 1N82x series zeners.
> These had a zener with the emitter of an NPN transistor against its
> cathode (for the tempco offsetting PN junction) in the device, and
> were used in the Fluke 731B, 732A, 332B/D, 335, and no doubt more.
> They are 4 terminal devices. Fluke "ovenized" them.
> Fluke service manuals only refer to them with an internal designation.
> My understanding is that these were "state of the art" prior to the
> National LMx99 (which was in turn followed by the LTZ1000).
You mean the ancient Motorola reference amplifiers?
I should also have some data on these.
These were discrete devices in hemetic packages welded together within
an overall 4 lead metal hermetic package.
Depending on the voltage the zener may have had one or more forward
biased diodes connected in series.


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