I would like to amplify a very low signal. Typically, the signal is from 1mV to 9.8mV (so a range of 8,8mV).
This signal is coming from a voltage divider (between the ground and the two resistors).
This signal will be amplifie to reach an amplitude max of 3.3V.
The bandpass needed if from DC to 5-8Hz.
The amplified signal will be numerized in a 16 bits ADC.
I think my major problem is the noise, I'm afraid that the little variations will be covered by noise. I know that I won't be precise at one LSB but I want to do the maximum to minimize noise error and measuring very very little variations.
So I have questions :
- I selected two amplifiers, an AOP (AD8571) and an instrumenation amplifier (AD8237). I don't know what's the best choice for the application.
- I will filter to remove maximum noise in high frquency (>5-8 Hz).
- It's best to filter before or after amplifier ?
- I think to use 2nd order sallen-key active filter, is it reaaly best to have 2 cells to have a fourth order ?
- For the supply of the voltage divider, is it really necessary to use a low-noise/very precise voltage reference to minimize the noise at the source ?
The AD8571 is a first generation zero-drift amp with high flatband noise.
Use an ADA4528-1 instead.