[volt-nuts] Trimming the LTZ1000 tempco

[Andreas Jahn]

Hello Will

> 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

I tried the influence of the 70k Resistor on tempco since 
I had to build mine of a 50K + a 20K precision WW resistor 
and wanted to save the 20K resistor.

The change in tempco on my LTZ1000A #1 is from about 48ppm/K 
with 70kOhms to 52ppm/K with 50kOhms.
(I measured this by changing the temperature setpoint voltage divider
from 12K5 + 1K to 12K5 + (1K || 22K) )

The schematic used you will find on 06.11.2010 on this list.
I have spent much time to get away common mode effects away
from the most sensitive point of the cirquit. (Wich is the setpoint
voltage for the temperature).

With best regards

Andreas