[time-nuts] Phase Noise of 74AC gates

Bruce Griffiths bruce.griffiths at xtra.co.nz
Fri Feb 19 22:54:12 UTC 2010

Martyn Smith wrote:
> Hi All,
> I read Garry's email about using the 74AC04 as a distribution amplifier.
> Did I read it right, does Gary say you will get -178 dBc/Hz at 10 kHz 
> offset???
> Being one of only 3 or 4 companies in the world that manufactures 
> distribution amplifiers that break the -170 dBc/Hz region at 10 kHz 
> offset, in my experience any logic gate or Op amp will limit you to 
> about -155 dBc/Hz at offsets of 10 kHz and beyond.
> I've tested many competitive units and very few people get below -155 
> dBc.
> I'm not about to say how we achieve -170 dBc/Hz phase noise, but we 
> definitely don't use op amps or logic gates!!
> Regards
> Martyn
Yes the claimed phase noise for the 74AC04 inverters is about 20dB lower 
than the literature would suggest.
There's probably some problem with the measurement setup.


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