I downloaded the spice model for AD8676 and tried to simulate the noise in LTspice.
My circuit is really simple (see attached pdf).
The opamp is connected as a unity gain buffer. The only resistor is an Rs from the positive input to ground.
I am using +/-15V supplies (I also checked with +/-5V supplies and get same results).
I then swept the Rs value from 1 to 1G and plotted V(onoise) at 1kHz.
From that I find:
The datasheet says
Vn = 2.8nV/rHz
In = 300fA/rHz
So the simulated voltage noise seems to be ~10x too high and current noise is 15x too low.
Am I doing something wrong or is there a problem with the model for AD8676?