Question

The zero level detector is one application of a

• A. Comparator
• B. Integrator
• C. Differentiator
• D. Summing amplifier

Hint:

A zero-crossing detector is the simplest way to turn a Sine wave into a Square wave of the same frequency.

Answer 1

The Correct Option is A

A zero-level detector (also known as a zero-crossing detector) is a circuit that identifies when an input signal crosses a threshold of zero volts. 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 $-V_{sat}$.

3. Conclusion: Because this circuit utilizes the high-gain switching capability of an Op-Amp to compare an input against a fixed zero reference, it is fundamentally an application of a

Comparator. It is widely used in frequency counters and phase meters.