In analog electronics, if the input to a voltage comparator is a sinusoidal (sine) wave, what general waveform shape will appear at the comparator's output under ideal operation?

Introduction:
A voltage comparator is designed to compare an input signal against a reference and rapidly switch its output high or low depending on which input is larger. This question tests understanding of how a continuous-time sinusoidal input is transformed by an ideal comparator into a two-level logic-like output, emphasizing threshold crossing behavior and slew-driven transitions rather than linear amplification.

Given Data / Assumptions:

• Ideal comparator with very high open-loop gain.
• Single reference threshold (often 0 V or Vref).
• No hysteresis (i.e., not a Schmitt trigger), unless otherwise stated.
• Input is a pure sine wave of sufficient amplitude to cross the threshold twice per cycle.

Concept / Approach:
The comparator saturates its output to one of two rails depending on the sign of the differential input. When a sine wave crosses the threshold, the output abruptly flips between its high and low saturation levels. Because the comparator does not reproduce the shape of the input but only its sign relative to the reference, the output becomes a two-level waveform (a rectangular or square-like wave).

Step-by-Step Solution:

Verification / Alternative check:
Counting threshold crossings: a sine has two crossings per period, giving a 50% duty cycle when Vref = 0 and the sine is centered. With nonzero Vref or offsets, duty cycle changes but the output remains rectangular because only the sign (not magnitude) is encoded.

Why Other Options Are Wrong:

• Ramp voltage: Requires integration, not comparison.
• Sine wave: Would be the input or an amplifier output, not a comparator's saturated output.
• Sawtooth wave: Requires a repetitive charge–discharge process, not simple thresholding.

Common Pitfalls:
Confusing a comparator with a linear op-amp stage; forgetting that slew and saturation dominate; assuming harmonically related wave shaping without threshold behavior; overlooking hysteresis effects of a Schmitt trigger (which affect switching points but not the rectangular nature).

Final Answer:
Rectangular wave.