Two diode at the inputs of opamps
It's because op-amps should have near 0 voltage difference between the inputs. The diodes are there so that a large voltage difference doesn't de-bias the input stage by causing the internal transistors to operate in non-linear modes. Sometimes those diodes are internal to the op-amp. Basically just input protection diodes.

That's one of the (many) reasons you don't want to use op-amps as comparators. Comparators will never have those diodes, while sometimes op-amp do have them, meaning that they will draw a lot of current and clamp when the input(s) swing.