Open-loop vs. closed-loop operation — feedback usage: Is feedback used in an “open-loop” operational amplifier circuit, or is open-loop explicitly the no-feedback condition used primarily for comparators and conceptual analysis?

Introduction / Context:
Op-amp applications are commonly divided into open-loop and closed-loop. Clear terminology prevents design errors. “Open-loop” means the output is not fed back to the input for linear gain-setting; the device runs at its enormous open-loop gain and quickly saturates, which is useful for comparator behavior but not linear amplification. This question asks whether feedback is used in open-loop circuits.

Given Data / Assumptions:

• Standard op-amp definitions (open-loop vs. closed-loop).
• Idealized large open-loop gain.
• No stability or slew considerations required for the concept.

Concept / Approach:
Open-loop operation by definition means no feedback path is applied to control the gain. Closed-loop operation introduces negative feedback to set a predictable, finite gain determined by external components. Therefore the statement “Feedback is used in an open-loop op-amp circuit” is incorrect because it contradicts the definition of open-loop.

Step-by-Step Solution:

Verification / Alternative check:
Comparator circuits are open-loop uses of op-amps: outputs rail high or low based on input polarity; no feedback sets a linear gain. Conversely, inverting/noninverting amplifiers are closed-loop examples with resistive feedback networks.

Why Other Options Are Wrong:

• Correct: Conflicts with the definition of open-loop.
• Only true for unity-gain buffers: Buffers require feedback (closed-loop) to achieve unity gain.
• Only true when offset is zero: Offset does not change the loop classification.

Common Pitfalls:
Using “open-loop” loosely to mean “no external resistor values given”; equating comparator behavior with linear amplification.

Final Answer:
Incorrect