[time-nuts] Noisy varactor diodes

gary lists at lazygranch.com
Wed Dec 19 06:57:25 UTC 2012

HP has a patent on this scheme. The paralleling of the diodes is for 
noise reduction. Personally, I would have rejected the patent since this 
is the kind of thing that is obvious to those skilled in the art.
> http://www.google.com/patents/US4621205?pg=PA1&dq=4621205&hl=en&sa=X&ei=J2DRUKDxF-vcigKtoIH4Ag&sqi=2&pjf=1&ved=0CDgQ6AEwAA#v=onepage&q=4621205&f=false

If surface states are the source of the noise, then it would take an 
annealing process to reduce the noise. I never made discrete diodes, so 
I don't know what kind of foo they use in processing power diodes versus 

Your typical analog IC has countless reversed biased diodes. I can't say 
I know of anyone who investigated them as a noise source, but in CMOS, 
low noise is a relative term.

It wouldn't surprise me if the closer you operate to the breakdown 
limit, the more noise you get. When you look at breakdown in the lab, 
you are viewing a pretty gross change in characteristics. But it could 
certainly be the case that as you approach breakdown, shot type noise 

On 12/18/2012 9:47 PM, Gerhard Hoffmann wrote:
> Am 18.12.2012 22:42, schrieb John Miles:
> Just curious, what was the 5065A acting like with the bad diode?  Mine
> seems
> to run quietly for days at a time, but then occasionally it generates
> excess
> low-level random noise for a period of hours to days (see image).  Every
> time I've tried to get serious about tracking the problem down, it stops
> misbehaving.  Did yours look like this?
> A Heisenbug. Observing it affects the outcome.
> Gerhard
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