An organic light emitting display comprising: a plurality of pixels at crossing portions of data lines (D1...Dm), scan lines (S1...Sn), and emission control lines (E1...En), each of the plurality of pixels comprising an organic light emitting diode for emitting light and a driving transistor configured to drive the organic light emitting diode; a sensor configured to sense degradation information of the organic light emitting diodes and mobility information of the driving transistors by measuring the voltage across the organic light emitting diodes; a converter configured to store the degradation information of the organic light emitting diodes and the mobility information of the driving transistors and to convert input data to corrected data by utilizing the degradation information and the mobility information; and a data driver configured to receive the corrected data output from the converter and generate data signals utilizing the corrected data to be supplied to the plurality of pixels via the data lines; wherein the sensor comprises sensing circuits, wherein each sensing circuit corresponds to one of the data lines, wherein each sensing circuit comprises: a current source unit configured to supply a first current to a corresponding one of the plurality of pixels; a first current sink unit configured to sink a second current from said corresponding one of the plurality of pixels; and a second current sink unit configured to sink a third current from said corresponding one of the plurality of pixels; wherein the converter is further configured to store the measured voltages and to perform the difference between the second voltage and the third voltage corresponding respectively to the second current and third current, so as to obtain said degradation information and mobility information. a plurality of pixels at crossing portions of data lines (D1...Dm), scan lines (S1...Sn), and emission control lines (E1...En), each of the plurality of pixels comprising an organic light emitting diode for emitting light and a driving transistor configured to drive the organic light emitting diode; a sensor configured to sense degradation information of the organic light emitting diodes and mobility information of the driving transistors by measuring the voltage across the organic light emitting diodes; a converter configured to store the degradation information of the organic light emitting diodes and the mobility information of the driving transistors and to convert input data to corrected data by utilizing the degradation information and the mobility information; and a data driver configured to receive the corrected data output from the converter and generate data signals utilizing the corrected data to be supplied to the plurality of pixels via the data lines; wherein the sensor comprises sensing circuits, wherein each sensing circuit corresponds to one of the data lines, wherein each sensing circuit comprises: a current source unit configured to supply a first current to a corresponding one of the plurality of pixels; a first current sink unit configured to sink a second current from said corresponding one of the plurality of pixels; and a second current sink unit configured to sink a third current from said corresponding one of the plurality of pixels; a current source unit configured to supply a first current to a corresponding one of the plurality of pixels; a first current sink unit configured to sink a second current from said corresponding one of the plurality of pixels; and a second current sink unit configured to sink a third current from said corresponding one of the plurality of pixels;