Data drivers and organic light emitting display devices having data drivers are provided in which a number of amplifiers for driving a display panel is reduced. A data driver includes an analog-to-digital converter, first and second amplifier circuits, a first switch coupled to an output of the first amplifier circuit, and a second switch and a third switch coupled to an output of the second amplifier circuit. The first switch is configured to selectively couple the output of the first amplifier circuit to a first data line and to second data line of a display panel. The second switch is configured to selectively couple the output of the second amplifier circuit to the second data line and to the analog-to-digital converter. The third switch is configured to selectively couple the output of the second amplifier circuit to a sensing line of the display panel.