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

Christopher Hoover ch at murgatroid.com
Mon Feb 5 00:54:25 UTC 2007


> The TI regulators are, from my perspective extremely noisy, one can do 
> much better at least for higher output voltages.
> They also don't have a high enough output for the TADD-1.

Agreed, that that regulator doesn't have sufficient margin for the entire
TADD-1.

I was suggesting using the low-noise high PSRR linear reg only to establish
the bias level.  

There are indeed better parts.  This one looks pretty good for an
integration solution (not include three C's):

http://datasheets.maxim-ic.com/en/ds/MAX6126.pdf

This app note, which filters the MAX6126 with an additional pass transistor
and opamp, shows how to get down to 6 nv/sqrt(hz):

http://www.maxim-ic.com/appnotes.cfm/appnote_number/3657

> < other circuit suggestions >
> This avoids blowing fuses if the supply polarity is reversed. 

Or a PZT.   We use a lot of them in the power circuit for hot plug sockets,
like on disk shelves.  (A fuse is cheaper wrt to the BOM, but the warranty
costs kill you.)

> The problems of instability and coupling of power supply noise into the 
> signal path were also present when single supply discrete transistor 
> amplifier were the norm.
> Quite elaborate bias divider decoupling circuitry was used to minimise 
> the effect.

Yeah, at some point a bipolar design becomes easier, right?

-ch






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