[time-nuts] NIST isolation amplifiers

Charles Steinmetz csteinmetz at yandex.com
Wed Nov 26 08:52:14 EST 2014

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,


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