[volt-nuts] A new LTZ1000A transfer standard is born

John Devereux john at devereux.me.uk
Sat Mar 2 06:57:11 EST 2013

Hendrik Dietrich <don_hendi at gmx.de> writes:

> Good morning fellow nuts,
> after a short planning and long wait times to get LTZ from china[1], PCB
> from the Ruhr valley[2] and resistors from the UK[3], I was no longer
> able to wait and slap everything together. 

Hello Hendrik,

Well done, I have been working on LTZ1000 circuits too, very
intermittently unfortunately...

> It is a clone of the Williams design in Linear Technology AN86 with
> 2x25K in parallel as R4, as suggested by Dr. Frank Stellmach from this
> maillist. The interesting resistors are General Resistance Econistors,
> the zener plus is buffered with a further LT1013 before breakout with
> 4mm copper-tellur receptacles[4].

Won't the buffer have too much drift and TC? In that same application
note he uses chopper stabilized amplifiers for this.

Hmm, LT1013 has guaranteed 2uV/K = 0.28ppm/K. But likely less than that,
and you could compensate it by fiddling with the tempco resistor in the
reference circuit. But what is the long term offset stability?
"0.4uV/month". Or 0.05ppm, compared to roughly 0.3ppm/sqrt(month) for
the LTZ1000. So should be fine if I did the sums right. And likely a
lower noise contribution than the chopper amps I have been looking at.



John Devereux

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