[volt-nuts] Trimming the LTZ1000 tempco

[Will]

Has anyone tried to minimise the LTZ1000 tempco? The unheated tempco
is high, so it could help to reduce the drift caused by the
imperfections of the temperature control system.

Datasheet page 6 shows a way to "null" the overall tempco

cds.linear.com/docs/Datasheet/1000afc.pdf

As far as I understand (most likely I don't) adding the R1 doesn't
much change the zener current. But the op-amp output voltage goes
higher to maintain the balance which increases the transistor Ic which
slightly changes the VBE tempco. But could we get the same result by
adjusting the 70k resistor instead? Adding a component is always a
source of drift. There is probably a reason to do it as shown in the
datasheet.

Will