Steve Nosko wrote:
. . .
Don't (some) zeners generate noise???...or is that only near the breakdown
reigion?

Some are very noisy. The noisiest I've seen have been ones in the 12 -
15 volt range when biased at considerably less than a mA. I've used one,
followed by a 50 ohm amplifier "pill" IC, as a broadband noise source to
see filter responses with a spectrum analyzer. The noise is easily
visible well up into the UHF region.

But all zeners generate some noise, so you have to use appropriate
filtering in sensitive applications. In my experience, though, band gap
references can be even noisier than a typical zener.

Roy Lewallen, W7EL