[time-nuts] AMC-123 patent (was: Re: Phase Noise of 74AC gates)

Rick Karlquist richard at karlquist.com
Sat Feb 20 21:07:14 UTC 2010

Bruce Griffiths wrote:
> Rick Karlquist wrote:
>> Bruce Griffiths wrote:
>>> He's made similar comments before.
>>> It actually isnt that difficult to achieve an isolation amplifier phase
>>> noise floor below -170dBc/Hz if one is careful to use appropriate
>>> parts,
>>> design techniques, and the input signal level is high enough.
>>> The real problem is verifying that performance.
>> The 10811 production engineers searched for a long time for
>> a low noise buffer amplifier and settled on the ANZAC AMC-123.
>> The data sheet refers to a patent that reads like
>> a construction article.  You can make your own if you can find
>> an old 2N5109 transistor.
>> Rick Karlquist N6RK
> The Tyco/MAcom version of the AMC-123 datsheet doesn't refer to a patent.
> Is a variant of a Norton CB transformer feedback amplifier?
> One would need to cascade a number of these to achieve a reverse
> isolation of 120dB.
> Whilst I dont have any 2N5109's,  I do have several 2N5943's.
> Bruce

Fortunately, there is a paper copy of the 1989 Anzac catalog
in the N6RK technical library.  Not everything is on the
internet.  The patent number is:


Yes, 2N5943 is interchangeable with 2N5109.  You could even
get away with an old 2N3866.  Do NOT substitute a microwave
transistor.  It will typically have higher base spreading
resistance (bad) and a uselessly high Ft for 10 MHz work.
For example, BFR90.

Any time-nuts subscriber in good standing should be able to
duplicate this design from the info in the patent :-).  This
patent is referenced in many amplifiers in the catalog.  There
are some amplifiers that are basically like the 123 on steroids.
Even higher intercept, but bring your heatsink, these are

Rick N6RK


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