[time-nuts] NIST isolation amplifiers

[Bruce Griffiths]

Almost. 1:1:2 (turns ratio) transformers used in each stage and 1:1 
transformer on input.  This allows a lower power supply voltage to be used.
One thing to watch with minicircuits transformers is core saturation due to 
dc flowing in the windings.
Bruce
On Wednesday, November 26, 2014 08:52:14 AM Charles Steinmetz wrote:
> Bruce wrote:
> >A single 2N2222 or equivalent transistor in a suitable circuit
> >dissipating about 200mW or so can achieve a reverse isolation of
> >35dB with distortion of around -40dBc (output +13dBm) with a gain of
> >unity, and an output impedance of 50 ohms with a PN floor of around
> >-180dBc/Hz or so.
> 
> For those wondering, I suspect Bruce had in mind something like the
> attached  (he posted the basic design a few years ago).  I built 8
> channels using toroids on FT37-61 cores.  I think the Mini-Circuits
> T622 should work, but I have not tried it.  The analyses are from my
> simulation, and the constructed unit performed similarly.  The Miller
> effect limits fan-out to about 10 for a 10MHz distribution
> amp.  [Note: the 50 ohm resistors on the outputs represent the
> external loads, and are not part of the amplifier.]
> 
> Best regards,
> 
> Charles