I'm trying to design a high-gain differential amplifier using 2x ADA4895 an RC filter (not shown), and an output buffer (AD8606) on the +ve and -ve lines. The simulation of the following schematic runs fine without the AD8606 buffers.
However, as soon as I connect the buffers, the simulation computation slows down so much that in 3 hours it only completed 0.2% of the calculation.
The same simulation with the same inputs with a different input stage opamp worked just fine. The input is +/-10mV centered around 4.7V and I'm powering the ADA4895 from 9.4V and ground single supply. The AD8606 is powered from 5.5V and ground.
I've tried scaling the resistors, introducing capacitors here-and-there, but nothing worked. What am I missing in the above topology that makes the simulation fail? Is there a way to fix it or I'm doomed? I could not find any obvious thing in the datasheet.