I've used spice model of AD8657 on LTspice. Then I get 40mV offset voltage between the inputs of AD8657 by .op analysis. Is the model correct? When I used the spice model of AD824, the offset voltage is around 40uV.
I had a quick run of AD8657 and AD824 DC parameters on LTSPICE, both offset voltage are within the datasheet spec which is 350uV for AD8657 and 100uV for AD824.
Please see below for my test setup and simulation results.
We usually model and characterize the amplifiers on the highest supplies available on the spec table. I recommend using +/- 9V on AD8657 and +/-2.5V on AD824.
Please try this on your simulation and let me know if we get the same results.