Due to being extremely low voltage noise devices, the AD8597/AD8599 input
resistance is omitted from the datasheet (Rev. C 12/09), as these devices are
typically used with impedances less than 2KΩ – 5KΩ.
The AD8597/AD8599 differential capacitance is about 15.4pF and the common mode
capacitance is about 5.5pF (Rev. C 12/09, page 4, table 2), with a Vsy of ±5V.