A compensation unit includes a current source unit, a current sink unit, a sensing resistor, a comparator, and a memory. The current source unit is configured to supply a first reference current to a first node. The current sink unit is configured to sink a second reference current from the first node. The sensing resistor is coupled between the first node and a second node. The comparator is configured to: compare a voltage at the first node with a voltage at the second node, and output a comparison result signal based on the comparison. The memory unit is configured to: store compensation data related to operational disparity of at least one organic light emitting diode and/or of at least one driving transistor, output the compensation data, and modify the compensation data based on the comparison result signal.