Hello everybody,
after reading the whole thread and some other threads and articles, i finished my first revision of a LM399H based reference. Or is it AD587LQ based?
At the end, i don't really know.
Few weeks ago i soldered a 100% copy of an SVR-T on a small chinese breadboard and since that time, i got 10,000.00V, drifting between 9,999.99 and 10,000.01V, depending of the room temperature.
I used simple 25ppm resistors and a 100 ppm trimmer with 200 ohms for the trimming of the AD 587.
Quick and dirty T.C. compensation is done with a 100k thermistor in series with a 220k fixed resistor (50 or 100ppm, don't know).
So i decided to use the combination of the LM399 and the AD587 as described in Joe Gellers patent, to add the stabilities of both parts.
I tried my best to avoid the known constructive errors, but i'm not sure, if i should use a ground plane on both layers for a better heat distribution
or if i should omit it for a better temperature isolation.
Please have a look at the pictures of both layers and tell me your opinions.
Thanks in advance
Frank