A customer asked a question about input impendence of sigma-delta ADC, AD7705.
Do you had any data about input impendence while with buffer or no-buffer?
The input impedance is several giga-ohms when the buffer is enabled. When the
buffer is disabled, the analog input pins are connected directly to the
switched capacitor input. These capacitors are only a few pF. Large R-C
combinations cannot be connected to the input pins in this case as they will
introduce gain error. The datasheet shows the R-C combinations that can be
connected to the AD7705.