When discussing the "standard" 399's 7V->10V design with a bipolar OP07 (not a chopper/AZ) we usually neglecting the need for a Vos nulling (here we talk always the nulling with the trimmer between the pins 1 and 8 ).
It has been indicated in some posts couple of times the TC of the Vos "will be zero when the Vos is nulled".
I've recently had a look into below paper from TI, which indicates the TC of the Vos actually does not depend on the level of "nulling". They even suggest an NTC thermistor in the external trim circuit.
Now, I want to trim off the Vos and its TC of my OP07 in my "standard 399" circuit.
My Qs:
1. the TI's range for the nulling Vos (OP07) with the trimmer is 4mV (DS) - it sounds to me even with a 10T trimmer (no padding resistors in series with the trimmer) to trim off say 50uV would be an uneasy exercise
2. after the nulling the TC of the Vos, like for example +1uV/C, will stay the same - is that correct??
3. how to make the nulling in the real "standard 399" circuit - I mean how to measure the input voltage offset has been nulled?