I also noticed the input impedance issue some time ago.? The model designer(s) of the universal opamp seem to have assumed that all opamps have MOS inputs wherein the input resistance is determined almost entirely by the impedance of the ESD protection structures to the supply rails.? Opamps with bipolar input devices have substantially lower differential input impedance than common-mode input impedance and this does manifest as performance differences in different circuit topologies.? The also have input bias currents, which are missing from all of the universal opamp models.
