AD8606 -- Meaning of noise density plots?

Brorson on Mar 27, 2018

I am investigating the 1/f noise behavior of the AD8606. Please look at figures 28 -- 30 in the datasheet, which show the voltage noise density (nV/rtHz) vs. frequency. There are three plots, each covers a different frequency range. Otherwise, the plots are taken for identical parameter values as far as I can tell.

Figures 28 and 29 make sense to me -- they asymptote to the same high-frequency value (about 6.7nV/rtHz). However, Figure 30 asymptotes to a different high-frequency value (15nV/rtHz), and the low end noise values don't match those in Figs 28, 29.

Any thoughts about how to interpret Figure 30?

Thanks,

Stuart

0 Gauzz

on Apr 3, 2018 12:11 AM
Hi,

I'm currently looking into this. I'll get back to you once the data is available.

Regards,
Goz
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0 Emman.A

on Apr 18, 2018 5:46 AM
Hi Stuart,

Figure 30 shows the noise density of around 14.9 nV/rHz at 100Hz. This value is hard to read on Figure 29 due to the 1kHz per division of the graph. I also admit that there is some discrepancy of the reading on figure 28 at 100Hz which is around 11nV/rHz but I think that is fine. You can also verify this value on page 7 of its datasheet under Noise Performance.

Now to interpret this data and convert to rms noise which will dictate the sensitivity of your circuit, I suggest to read this article which tackle this topic in details: http://www.analog.com/media/en/training-seminars/tutorials/MT-047.pdf

I also recommend to watch this video which convert the voltage noise to RMS noise.

https://www.youtube.com/watch?v=ywChrIRIXWQ

Let me know if you have further questions.

Best regards,

Emman
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0 Brorson on Apr 18, 2018 5:13 PM

Hi --

Any results yet?
Thanks,

Stuart
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