We are currently using OPA1632's to drive 8 analog input channels on the ADS1278 with a 0.25 gain, wired as recommended in the ADS1278 datasheet, on page 38 lower left: Basic Differential Input Signal Interface. We are noticing that the OPA1632 circuit in the datasheet is not a high-impedance buffer, and because of this, a low-impedance voltage source is pulled down by the OPA1632 (or rather the resistors around the OPA1632). We are thus getting incorrect voltages reported by the ADS1278.
What is the most effective way we can modify the OPA1632 circuit in order to provide high impedance on the input source, but yet still maintain the high resolution we need at the ADS1278, and also still properly drive the +/- input channels on the ADS1278?
Thanks!
