An operational amplifier (op-amp) can operate in two main configurations: 1. Open-Loop Configuration: The op-amp operates without any feedback from output to input. It has very high gain (often >100,000), so even a small difference between the inputs drives the output to saturation (either max positive or negative voltage). Not suitable for analog linear applications; mainly used for comparators. 2. Closed-Loop Configuration: A feedback network (usually negative feedback) connects the output to the inverting input. This stabilizes the gain and allows for linear operation (e.g., amplification, filtering, integration). Common applications include amplifiers, filters, integrators, and buffers. Key Difference: Open-loop: Very high gain, non-linear, used for comparison. Closed-loop: Controlled gain, linear, used for signal processing.