I'm working on my first (10V) voltage reference, it is built around an LM399 and LT1001. I was using 10ppm resistors. After a lot of noise and drift, the drift seemed to settle more and more now, I'm getting around 10uV stability. This is after running for about a week. This is not battery powered, and done quite hacky for a first prototype. What is your experience with drift and LM399?
My next design is going to use an LT2057, for the op amp, and more stable resistors, to see what kind of results I'll be getting. If you have any feedback, please let me know. My goal is to get a stable and accurate 10.00000V.