[time-nuts] Distribution amp - Use a video amp unit ?
bruce.griffiths at xtra.co.nz
Sun Mar 25 18:14:43 UTC 2012
> I need a distribution amp for my Tbolt , with 6..8+ outputs
> The TAPR-1 is NA , and the successor status is ???.
> I need it for distributing 10Mhz ref-clock to Counters
> (HP,Racal,Phillips), a Rigol Sig-gen& maybe Oscilloscopes etc.
> It's for "better than ocxo/hobby use" , and not Tnut (ps accuracy).
> I have seen suggestions for using a video distributiution unit.
> But in my part of the world (EU) , there isn't a lot on "eby".
> I have seen some RGB amps , and was wondering if i could use those ?
> Could i use a 1:6 RGB unit for : Tbolt on R , FEI-5680A on G - and ?? on
> B ?
> I'm not experienced (yet) in the analog domain.
> If i go (simple diy) Would this one work (also wo. the trafo's) ?
> I do have some trafo's on an old 10Mhz 8-chan Hub , that i might be able
> to salvage if needed.
> Thanx for any input/hints
> CFo - T-Nut beginner Denmark.
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
Winding your own transformers isnt particularly difficult if you have
suitable (binocular) cores.
The discrete amplifier shown has a class AB output stage, lower
distortion is possible if a class A output stage is used (requires an
extra resistor between the output stage emitters and an additional diode
in series with the LED).
With a Class A output stage the 39 ohm resistors should be replaced by a
a pair of 100 ohm resistors to match the load.
Significantly lower distortion is possible if feedback from the output
to the input stage is used.
If the feedback gain is unity (or less) at dc higher AC gains won't
significantly degrade the close in phase noise.
A different amplifier topology using the same number of transistors will
allow a higher reverse isolation to be achieved.
One problem with video distribution units (aside from the relatively
high phase noise floor) is the limited output drive available. For some
purposes 16-20dBm outputs are desirable.
More information about the time-nuts