[time-nuts] NIST isolation amplifiers

Bruce Griffiths bruce.griffiths at xtra.co.nz
Wed Nov 26 12:25:04 EST 2014

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.
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

More information about the time-nuts mailing list