[time-nuts] TADD-1 Design (was Re: Stepping up the output of an OCXO (Dr Bruce Griffiths))

[Christopher Hoover]

> The power supply noise may also limit the performance.

This is my major concern with the design.  

Any noise on the supply rail goes into the first stage via the bias network,
and is transferred at whatever gain to the output.

I noticed that when I used a particular bad wall wart to run one of my
TADD-1's, I saw power supply noise on the outputs.  

I hacked one of my TADD-1's to decouple the bias from the power supply, and
I added a wide-band bead in front of the regulator.  Those changes helped
considerably.  (I also tossed out that bad wall wart.)

Using a high PSRR reference for the bias would be worth investigating.
There are a number of these on the market, intended for RF apps.  E.g.,
TPS794xx family.  http://focus.ti.com/docs/prod/folders/print/tps79401.html

There's a good treatment of biasing single-supply op amps here: 
http://www.analog.com/library/analogDialogue/archives/35-02/avoiding/index.h
tml

-ch