[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,
Charles
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