1. Operational Principle of a Comparator: A comparator is an open-loop Op-Amp circuit that compares two input voltages ($V_1$ and $V_2$). If $V_1 \gt V_2$, the output saturates to the positive supply ($+V_{sat}$); if $V_1 \lt V_2$, the output saturates to the negative supply ($-V_{sat}$).
2. Configuration for Zero-Level Detection: In a zero-level detector, one input of the comparator (typically the inverting terminal) is connected directly to
Ground (0V). The signal to be monitored is applied to the other terminal.
• When the signal is even slightly above 0V, the output is $+V_{sat}$.
• When the signal is even slightly below 0V, the output is $-V_{sat}$.