Overvoltage protection using opamp
Notice the 75 ohm BNC connector. It is likely weak AF to RF signals with not much drive current. If D1 and D2 are 1N4148 then response time is nanoseconds, and they prevent the 75 ohm line from seeing the capacitive load of the comparators outputs. The upper comparator clamps any negative voltage, while the lower comparator clamps if voltage is greater than 5.0 volts.
This bi-directional voltage clamp is fast to respond with little capacitive loading of the signal line. It makes sure down-stream devices do not get voltage peaks &lt; zero volts or &gt; 5 volts.
Note that this part number is a 20 MHZ quad op-amp with a 11V / uS slew rate, so it cannot protect pulses faster than a few MHZ. Maybe not very good clamp if frequency is over 100 KHZ.