[volt-nuts] Trimming the LTZ1000 tempco

Will willvolts at gmail.com
Sat Oct 1 08:13:10 UTC 2011

> The change in tempco on my LTZ1000A #1 is from about 48ppm/K
> with 70kOhms to 52ppm/K with 50kOhms.

A rough estimation:
Change in Ic when R1 is set from 0 to max value 200 ohms is equivalent
to changing the 70k resistor to 60k. I haven't prototyped or
simulated, so there can be more complex interactions that I haven't

Maybe it is not even possible to "null" the tempco in a way simple
temperature compensated zeners allow to do that? The trick in the data
sheet seems not to be very effective.

Another alternative is to adjust the 120 ohm resistor which changes
the zener current.

It is surprising how slavishly all equipment manufacturers have copied
the original datasheet circuit during the last 20+ years.


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