An analog-to-digital converter includes an input buffer connected to an input terminal receiving an input signal through a first sampling switch, a comparator connected to the input buffer, a sampling capacitor connected between the input buffer and the comparator, and connected to a second sampling switch, a digital-to-analog converter connected to the comparator, and a controller, connected between the comparator and the digital-to-analog converter, configured to output a signal to the digital-to-analog converter based on the comparator.