[time-nuts] TADD-1 Design (was Re: Stepping up the output of an OCXO
Dr Bruce Griffiths
bruce.griffiths at xtra.co.nz
Mon Feb 5 17:28:41 EST 2007
Christopher Hoover wrote:
> Agreed, that that regulator doesn't have sufficient margin for the entire
> 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):
> This app note, which filters the MAX6126 with an additional pass transistor
> and opamp, shows how to get down to 6 nv/sqrt(hz):
A simpler solution should be possible.
Since both the input and the outputs are transformer coupled, the
circuit ground plane could sit at half the supply voltage.
There need be little dc current flowing into or out of the circuit
ground plane so a simple resistive divider should suffice to bias it at
the desired voltage.
If all RF loads within the circuit are returned to the circuit ground
plane then most of the resistive dividers used to set opamp input dc
levels can be eliminated.
This complicates testing in that either a floating dc input supply would
be necessary or differential probes with adequate common mode rating
would be required.
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