Anders wrote:
How is that calculated? I only get this far: 9.6nV/sqrt(Hz) into a 50R load is 1.8e-18 W/Hz or -147.3 dBm/Hz what then?
As I said on Dec. 18 in response to the original post, the in-band (10MHz) noise is NOT the main problem with respect to AM and PM noise. The main problem is the BASEBAND noise (near DC, say, 0.1Hz--10Hz). And the AD8055, as well as the MAX477 originally used in the TADD-1, are absolutely horrible in this regard. Both of them have noise densities > 1,000nV/sqrtHz at 10Hz (and even worse below 10Hz).
See my earlier post for a brief explanation of why this is so, and how baseband noise is converted to AM and PM noise in the RF signal band. There are also more in-depth explanations in the archives. One search term you can use is "PM conversion."
For low AM and PM noise, you want an opamp with a noise density of 10nV/sqrtHz, or lower, *at 10 Hz*. The ADA4899, LME49713, and AD8010 are three possible choices (these days, there are many others, as well).
Best regards, Charles _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
