Schmitt trigger fundamentals: Identify the correct characteristics of a Schmitt trigger comparator stage used for noise-immune switching.

Introduction / Context:
A Schmitt trigger is a comparator circuit with hysteresis used for cleaning noisy or slow-ramping input signals. This question checks recognition of its defining traits.

Given Data / Assumptions:

• Noninverting or inverting Schmitt topologies exist.
• Two distinct thresholds: VT+ (rising) and VT− (falling).
• Feedback network sets hysteresis width.

Concept / Approach:
Positive feedback shifts the effective switching threshold depending on output state, creating two trip points. This hysteresis rejects small noise around the threshold and eliminates chatter.

Step-by-Step Solution:

Verification / Alternative check:
Plot the transfer with arrowed path; observe different thresholds on up and down sweeps.

Why Other Options Are Wrong:

• Has two trip points: Incomplete—does not mention the cause (positive feedback).
• Is a zero crossing detector: A basic comparator without hysteresis fits zero-crossing; Schmitt does not switch exactly at zero.
• Has positive feedback: True but incomplete—must also mention two trip points.

Common Pitfalls:
Confusing Schmitt triggers with simple comparators and assuming a single threshold.

Final Answer:
has two trip points and positive feedback