A comparator includes a first-stage circuit, a second-stage circuit, a first switching circuit and a second switching circuit. The first-stage circuit includes a first input circuit and a second input circuit. The first switching circuit is configured to control the conduction of the first input circuit, and the second switching circuit is configured to control the conduction of the second input circuit. The first input circuit is configured to generate a first differential signal in a sampling phase when being switched on. The second input circuit is configured to generate a second differential signal in a sampling phase when being switched on. The second-stage circuit is configured to amplify and latch the first differential signal or the second differential signal in a regeneration phase to output a comparison signal.