Operational Amplifier Fundamentals Unit 8 – Voltage Comparators
This circuit illustrates zero crossing operation: U1 is zero based because its (+) input is
connected to circuit common.
If VI equals 0V, then VD equals 0V, and U1 is not saturated.
If VI is slightly above or below 0V (circuit common), VO is at negative or positive saturation,
and VD is greater than 0V.
Open-loop comparator configurations are not practical because of the saturation characteristics
of op amps: slew rate limits and large voltage swings.
Op amp comparators can operate in closed-loop configurations. Feedback limits the level of
voltage change and introduces hysteresis.