Op-Amp Comparator Circuit
An operational amplifier (op-amp) comparator circuit is a type of electronic circuit that compares two input voltages and produces an output voltage based on the comparison. The output voltage is typically either high or low, representing a digital logic level.

No Feedback
The correct answer for this question is option 'A', which states that an op-amp comparator circuit employs no feedback. This means that there is no connection between the output and the inverting or non-inverting input of the op-amp.

Explanation
Op-amp comparators are designed to have very high gain and very high open-loop voltage gain. When the input voltage at the non-inverting terminal of the op-amp is greater than the voltage at the inverting terminal, the output voltage of the comparator goes to its positive saturation level. Conversely, if the voltage at the inverting terminal is greater, the output voltage goes to its negative saturation level.

Positive Feedback
Positive feedback is a configuration where the output of a system is fed back to the input with the same polarity, amplifying the input signal. Although positive feedback can be used in other op-amp circuits, it is not utilized in an op-amp comparator circuit.

Negative Feedback
Negative feedback is a configuration where the output of a system is fed back to the input with the opposite polarity, reducing the overall gain and stabilizing the circuit. While negative feedback is commonly used in various op-amp circuits, it is not employed in an op-amp comparator circuit.

Conclusion
In conclusion, an op-amp comparator circuit does not employ any form of feedback. The output of the circuit is determined solely by the voltages at the inverting and non-inverting inputs of the op-amp. When the input voltage at the non-inverting terminal is greater, the output voltage goes to its positive saturation level, and when the input voltage at the inverting terminal is greater, the output voltage goes to its negative saturation level.