A comparator has a first terminal, a second terminal, and an output terminal. A selection circuit is coupled to the first terminal. A calibration circuit is coupled to the output terminal and the second terminal. The comparator is configured to operate in a first mode when the selection circuit provides a first input signal to the first terminal and the calibration circuit provides a second input signal to the second terminal. The comparator is configured to operate in a second mode when the selection circuit provides a first calibration signal to the first terminal and the calibration circuit provides a second calibration signal to the second terminal based on an output signal at the output terminal. The comparator generates the output signal based on the first calibration signal and the second calibration signal.