Feedback mode identification (repaired): Without the actual schematic or signal routing, can we conclude that “this circuit is operating in closed-loop mode” (i.e., output fed back to an input to set defined gain/response)?

Introduction / Context:
An op-amp operates in “closed-loop mode” when some form of feedback (usually negative) connects output to input to define gain, bandwidth, and linearity. In “open-loop mode,” there is no external feedback path, and the very high open-loop gain makes the amplifier saturate with tiny differential inputs. This repaired question tests your ability to recognize when insufficient information prevents classification of operating mode.

Given Data / Assumptions:

• No schematic, feedback network, or node labeling is provided.
• We do not know if any resistor, capacitor, or network returns a fraction of the output to the inverting or non-inverting input.
• We assume a generic op-amp and generic source.

Concept / Approach:
Determining closed-loop operation requires identifying a feedback path and a reference node. Typical examples include inverting/non-inverting amplifiers, integrators, differentiators, and filters, all of which show a clear path from output to an input. Without the schematic, one cannot verify the presence or polarity of feedback or whether the device is saturated in open-loop.

Step-by-Step Solution:

Verification / Alternative check:
Given a schematic, derive the transfer function by writing node equations around the feedback network. Absence of a feedback term in the transfer indicates open-loop operation.

Why Other Options Are Wrong:

Common Pitfalls:
Assuming all op-amp circuits are closed-loop; overlooking intentional open-loop comparators that use op-amps.

Final Answer:
Cannot be determined from the information provided