Marco Reps has an interesting article on low noise amplifiers: Ultralow Noise Tester: 9V Battery vs. 7805 vs. LTZ1000 https://www.youtube.com/watch?v=XpbDMo8an5w - uses ADA4523: $3.030 Mouser, Digikey, 4.2 nV/sqrt(Hz), RRIO, 100pA Ib - Datasheet https://octopart.com/search?q=ada4523 Cross-correlation would improve noise floor. Hard to get down to Gerhard's level, but maybe doable. 1. Here is a brief explanation of how cross-correlation works: "Understanding Phase Noise - the Cross Correlation Method" https://www.youtube.com/watch?v=Sf7qiysPFbQ 2. The benefit of cross-correlation depends on how long you are willing to wait. From "TSP #162 Tutorial on Theory, Characterization & Measurement Techniques of Phase Noise" https://www.youtube.com/watch?v=SOHjFtw0sgo each 5db of improvement requires an order of magnitude increase in the number of correlations. dB 5 10 15 20 25 30 35 40 N 10 100 1000 1E4 1E5 1E6 1e7 1e8 So going from -180dBc/Hz to 220dBc/Hz would require 1e8 correlations. 3. Nobody would wait that long. But how many correlations do you need? A commonly accepted figure is your measurement noise floor has to be at least 10 dB below the noise you are trying to measure. We could pad that by 5 db, which would require 15 / 5 = 3 1e3 = 1000 correlations. That is not too bad. 4. It is interesting to note the Holsworth HA7062C Phase Noise Analyzer goes to a maximum of 1024 cross-correlations. 100 correlations (-10dB) takes 7 min, 9s at 10 MHz. https://holzworth.com/Portals/0/HA7062C_Web_Datasheet.pdf 5. Finally, "Frequency Signal Source's PN (Phase Noise) Measurements Challenges and Uncertainty", by Ulrich L. Rohde, has some very important information on cross-correlation errors. This file is at https://www.mrmonett.com/pdfs/2015-IFCS-Rohde-Oscillator-noise.pdf -- MRM
Ultralow Noise Tester: 9V Battery vs 7805 vs LTZ1000
Started by ●April 13, 2022
Reply by ●April 14, 20222022-04-14
On Thursday, April 14, 2022 at 3:02:14 AM UTC+10, Mike Monett wrote: <snip> https://www.analog.com/en/parametricsearch/11010#/p4007=300n|2u https://www.analog.com/media/en/technical-documentation/data-sheets/ltc6655-6655ln.pdf It's quieter than even the LTZ1000. And quite a lot cheaper. I suspect that the LTZ1000 parts are only being made for the legacy market, where it's cheaper to pay through the nose for a drop-in replacement than it would be to change the board to accommodate something newer and marginally better. -- Bill Sloman, Sydney