ADR421 has been around a while and is almost as good, at around the same price. I think it's a jfet thing.
Vref TCs in the low ppm range require corresponding resistors!
The Intersil floating-gate things are cool.
John
Thanks for the steer. The AD ones run off the delta-Vgs of two JFETs, running at the same drain current and identical except that one of them has had two channel implants. Nice idea--buried like a subsurface zener, so it's away from surface states, and the delta-V is much bigger than in a bandgap. The TC is smaller too, so less of the (noisier) compensation voltage is needed.
They don't tell you the details of the temperature compensation, which is obviously one of the crown jewels.
Usually at least one, to provide a standard current for an end-to-end calibration.
Harder to use than they look, though, if you really want the best performance.
Cheers
Phil Hobbs
(Posting from my new Thunderbird installation with all my old emails, finally.)
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