[volt-nuts] Some questions to zeners (1N823-1N829)

[Ed Breya]

Don't bother with TC zeners, especially for battery operated equipment. 
There are lots of nice IC references available from Analog Devices, 
Maxim, Linear Technology, TI, an so on, that will run rings around TCZs 
- you probably haven't seen the right one yet. The TCZs will only 
provide near zero tempco at one temperature only, so would have to be 
ovenized to get best performance. They also have an initial voltage 
tolerance up to a few percent, so the circuit would need tweaks and 
maybe amplification that add more error yet. I doubt that any TCZ will 
match an LM399 even with very elaborate circuitry to support it.

I think the Maxim MAX3650 family would be hard to beat for a low power 5 
V reference - my super-duper voltage standard (yet to built) will use 
four of them averaged together, and operated at constant temperature.

If you state what kind of performance you're looking for, it would be 
easier to make recommendations.

Ed