Ok so the amplifier can include a 20hz low pass filter. That will certainly help the noise.

At 10 Hz, a 20 Hz single pole lowpass filter will introduce an error of 11%. -ish.

ak

 

At 10 Hz, a 20 Hz single pole lowpass filter will introduce an error of 11%. -ish.

If that's a problem, you can increase the bandwidth some without increasing the noise greatly since wideband noise (white) is proportional to the square-root of the bandwidth.
A 2 or 3 pole filter would also help, of course.

 

From 0.5 uV to 3 V (A/D input range) is a gain of 136 dB, or 6 million. That's a lot. Normal opamp circuits cannot do this. You probably are looking at a composite amp configuration, with one opamp type as the high-precision front driving another opamp for additional gain.

CAZ - Commutating Auto-Zero. This is an amplifier technique used for low voltage, low frequency signals. Other names are chopper-stabilized, chopper amp, switched capacitor. etc. It reduces input errors to sub-microvolt levels. The Intersil ICL7650 was one of the first. Analog Devices calls theirs "Zero-Drift" amplifiers.

https://r.search.yahoo.com/_ylt=AwrEze0B0UNicxwAJTBXNyoA;_ylu=Y29sbwNiZjEEcG9zAzEEdnRpZAMEc2VjA3Ny/RV=2/RE=1648640386/RO=10/RU=http://www.cse.psu.edu/~kxc104/class/cse577/11s/lec/S04AmpOffset.pdf/RK=2/RS=dpedt3gdE0Skoar40vtYNNADjEA-

ak

 

If that's a problem, you can increase the bandwidth some without increasing the noise greatly since wideband noise (white) is proportional to the square-root of the bandwidth.
A 2 or 3 pole filter would also help, of course.

1/f noise will dominate at those frequencies.