I am using the ISO224ADWVR, with VDD1 = 5.5 V and VDD2 = 5 V. A simplified representation of my design below. When I apply 100 V to IN+, I measure 11.21 V at the input (pin 2) of the amplifier (as expected), and an output of 3.800 V (across pins 7 and 6). The ideal output is 3.737 V, so this represents an error of +1.7%. This error is greater the initial gain error specification of +/-1% at 25 °C. (I have verified that the input offset voltage is less than 3 mV, well within specification). I have observed this behavior this on multiple devices, with various voltages applied to the input. In all cases the gain error is higher than expected (> 1%). In my design, the ISO224ADWVR is normally connected to a difference amplifier, which presents a 200-kohm effective load. As an experiment, I removed the load altogether, but the output remained the same as before (i.e., the gain error was still higher than expected).
