An integrated circuit includes a reference voltage level setting circuit and a reference voltage generation circuit. The reference voltage level setting circuit is configured to set a level of an input reference voltage to a preset level in a power-up period or a self-refresh mode. The reference voltage generation circuit is configured to select one of a plurality of reference voltages and output the selected reference voltage as the input reference voltage when the power-up period is ended and an operation mode is not in the self-refresh mode.