I'm working on a sensor signal conditioning circuit. The sensor output has a 2.5V DC bias with a peak-to-peak voltage swing of about 50mV. The signal output is put through a demodulator and then filter (LPF) to obtain a DC voltage proportional to the out of the sensor. The problem is I need to be able to sense very small changes in the AC voltage output from the sensor (~ 2mv-5mV peak-to-peak changes). I'm new to signal conditioning and processing sensor outputs so I was wondering if anyone here knows how I can do this. I want ot learn about the basics and theory behind how to amplify the signal. Currently my DC output goes from about 2.467V to 2.561V (with the midpoint being about 2.514V, the DV bias). I need to translate that into a DC voltage swing of 0V to 5V, or something better than 2.467V to 2.561V. The way I'm thinking about doing this gaining the AC voltage BEFORE the LPF. I'm currently trying this approach but it isn't working because my output signal is all distorted after the AC gain.