Patent ID: 8400380

Claim:
An organic light emitting display device comprising: a scan driver for driving scan lines and light emitting control lines; a data driver for selecting any one gamma voltage of a plurality of gamma voltages corresponding to bit values of externally supplied data and generating data signals; a pixel coupled to a reference power, a first power, and a second power, the pixel configured to compensate for a voltage drop of the first power using the reference power; and a gamma voltage controller for comparing a voltage value of the reference power with that of a comparative power having a target voltage value of the reference power to generate a comparison result and controlling voltage values of the gamma voltages in accordance with the comparison result, wherein the gamma voltage controller comprises: a gamma unit for generating the gamma voltages; at least one comparator for comparing the voltage of the reference power with that of the comparative power; a subtractor for obtaining a voltage difference between the reference power and the comparative power in accordance with a comparison result of the at least one comparator; and a controller for controlling the gamma unit in accordance with the comparison result of the at least one comparator and the voltage difference.