Buffer Op Amp to Analog-to-Digital Converter Design: AC Coupled Single-Ended Input, Single Supply, Single-Ended Op Amps, Single Input to ADC

Problem:
How do I buffer the input of an Analog to Digital Converter (ADC) when I have an AC coupled single-ended input, single power supply, single-ended op amps, and single input to ADC?

Solution:


Double click on schematic to enlarge.

This circuit differs from the previous implementation in that the gain stage is inverting, and common mode voltage is injected into the non-inverting input of the op amp instead of being derived from Ref_A and Ref_B. It has the advantage of having an accurate common mode voltage that comes directly from the ADC, but the disadvantage that the buffer circuit introduces a phase shift of 180°.