Buffer Op Amp to Analog-to-Digital Converter Design: AC Coupled Single-Ended Input, Dual Supply, Single-Ended Op Amps, Single-Ended 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, dual power supply, single-ended op amps, and single-ended input to ADC?

Solution:


Double click on schematic to enlarge.

The ADC IN- input is connected to the common mode output of the ADC, and decoupled with C3. This sets the input range of the ADC as the common mode voltage to +Ref_A. The input source is coupled to the non-inverting input of the op amp. Non-inverting stage gain is set by R2 and R1. The op amp stage output is ac coupled through capacitor C1. The local virtual ground for IN+ is created from Ref_A and Ref_B though resistors R3 and R4, which should be equal in value. R5 and C2 are ADC compensation components.