Buffer Op Amp to Analog-to-Digital Converter Design: AC Coupled Single-Ended Input, Dual Supply, Single-Ended Op Amps, Differential 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 differential input to ADC?

Solution:


Double click on schematic to enlarge.

An inverting and a non-inverting op amp gain stage are used to present two polarities of an input signal to a differential input ADC. The resistors R1 and R2 set the inverting gain of the top op amp. The bottom op amp is a non-inverting gain stage. R4 and R3 set the stage gain, which must match the top gain stage. R5, R6, C3, and C4 are ADC compensation components. C1 and C2 are DC blocking capacitors, which allow a split supply op amp to interface with single supply ADC, or allow a single supply op amp with a virtual ground at one voltage to interface to an ADC with a different common mode voltage. R7 through R10 must be matched, because they create a common mode voltage for the IN+ and IN- voltages off of the top and bottom reference voltages.