QWhat are the implications of having unbuffered differential reference inputs?
AThe unbuffered reference input provides a high impedance, dynamic load. Because
impedance of each reference input is dynamic, resistor/capacitor combinations
on these inputs can
cause dc gain errors depending on the output impedance of the source that is
driving the reference
inputs. Reference voltage sources, like those recommended (AD780) will
typically have low
output impedances and therefore decoupling capacitors on the REFIN(+) and
would be recommended. Driving the reference input voltage across an external
resistor, as in many
ratiometric configurations, will mean that the reference input sees a
significant external source
impedance. External decoupling on the REFIN(+) and REFIN(-) pins would not be
in this type of circuit configuration.