A regulator includes a switch array, a feedback circuit, first and second voltage-controlled oscillators, and a switch driver. The switch array generates an output voltage based on a number of enabled switches from among a plurality of switches. The feedback circuit generates a feedback voltage which depends on a level of the output voltage. The first voltage-controlled oscillator generates a first signal having a first frequency which depends on a difference between a reference voltage and the feedback voltage. The second voltage-controlled oscillator generates a second signal having a second frequency which depends on a difference between the feedback voltage and the reference voltage. The switch driver determines a turn-on time point of each of the plurality of switches based on the first signal and determining a turn-off time point of each of the plurality of switches based on the second signal.