[time-nuts] SMD TADD-1 distribution amplifier - seeking comments and suggestions?

Bruce Griffiths bruce.griffiths at xtra.co.nz
Mon Nov 30 17:54:43 EST 2015

U101 only needs to have a gain of 1 at dc so replace R104 and R105 with a capacitor connected to ground.
Adjust the other components of the gain determining network accordingly.Also the junction of the power supply divider R102 and R103 should be heavily capacitively bypassed to ground and a resistor placed between this junction and U101's noninverting input.

Excess Sub Hz PN is usually due power supply noise or thermal fluctuations due to air currents/ convection.
Most of the so called super regulator circuitsĀ  should be more than quiet enough with an LM329 reference.A damped LCR filter at the input will improve the PSRR at switchmode output frequencies.


    On Tuesday, 1 December 2015 9:02 AM, Anders Wallin <anders.e.e.wallin at gmail.com> wrote:

 HI all,
I need to build a few distribution amplifiers (>90% for 10MHz, sometimes
maybe 5MHz) and instead of reinventing the wheel I decided to try to
modernize the TADD-1 into an all (almost) SMD design. Here are some draft

Does this sound/look reasonable or crazy?
Any suggestions for op-amps to try and/or compare to the AD8055?
What causes the extra phase-noise below 1 Hz offset in John A's result:

Suggestions for a low noise DC-regulator circuit? The 12-24VDC supplied to
this board will most likely come from a switched-mode PSU, so filtering of
common-mode noise is mandatory.
I found the TI LP38798 shown in the schematic by googling - if someone has
a proven a measured design that would be a safer choice. In any case more
filtering (e.g. ferriites) is probably a good idea.

This design will be available on my blog or on github when it is done - if
anyone is interested.

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