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

Bob Camp kb8tq at n1k.org
Mon Nov 30 16:49:39 EST 2015


Hi

Somethings to consider:  

How quiet are the sources you will be running through this amplifier?

How predictable are the levels of the sources? 

How important is isolation?

Do you need lowpass / bandpass filtering (are there other RF sources running around?)?

Is ESD on the coax an issue (do you need a high value resistor here or there?) ?

Bob

> On Nov 30, 2015, at 3:02 PM, 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
> sketches:
> http://www.anderswallin.net/2015/11/frequency-distribution-amplifier-plans-a-k-a-smd-tadd-1/
> 
> 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:
> https://www.febo.com/pages/amplifier_phase_noise/amplifier_phase_noise.png
> 
> 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.
> 
> Thanks,
> Anders
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