Provided is a readout integrated circuit including a sensor signal processing unit receiving sensor signals from a plurality of sensors and converting respectively the sensor signals into voltage signals, a signal converting unit respectively converting the voltage signals into digital signals, a digital signal processing unit outputting digital signals processed in response to the voltage signals and a switching control signal, a power supplying unit generating an internal voltage for operating the signal converting unit and the digital signal processing unit, and a reference sensing voltage for operating the sensor signal processing unit, and a switch unit operating in response to the switching control signal, wherein the switch unit includes switches respectively corresponding to the plurality of sensors and a current amount applied to each sensor is adjusted in response to operation times of the switches.