Comparator basics — Evaluate: “A comparator outputs a logic HIGH or LOW strictly based on which input voltage is greater.”
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ACorrect
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BIncorrect
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COnly true for differential amplifiers
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DTrue only with positive feedback
Answer
Correct Answer: Correct
Explanation
Introduction / Context: Comparators are threshold devices that decide which of two analog voltages is larger. They form the basis of zero-crossing detectors, window comparators, and many ADC architectures. The essence is binary: one of two logic states is produced according to the sign of V_plus − V_minus.Given Data / Assumptions:
- Comparator has two inputs, often labeled non-inverting (+) and inverting (−).
- Outputs saturate near logic rails or defined logic levels via a separate interface.
- No intentional hysteresis unless added (some parts integrate it).
Concept / Approach: The comparator evaluates the instantaneous difference between inputs. If V_plus > V_minus, output drives HIGH; if V_plus < V_minus, output drives LOW (or vice versa depending on output polarity). Adding positive feedback turns it into a Schmitt comparator with hysteresis but the fundamental decision remains a simple magnitude comparison.Step-by-Step Solution:
Define reference voltage on one input; apply measured signal to the other.When measured signal crosses the reference, the output toggles quickly.Use pull-up or push-pull output stage to interface with logic as required.Verification / Alternative check:
Oscilloscope plots show a clean digital transition at the threshold crossing.Why Other Options Are Wrong:
Incorrect: Confuses comparator behavior with linear amplification; comparators are decision-making devices.Only true for differential amplifiers: A comparator is a specific form of differential decision element; statement applies generally.True only with positive feedback: Hysteresis improves noise immunity but is not required for basic comparison.Common Pitfalls:
Feeding signals outside input common-mode range; outputs then misbehave.Expecting linear output; comparators are not op-amps in linear mode.Final Answer:
Correct