Patent ID: 8405587

Claim:
A method of programming a pixel circuit that drives a current-driven organic light emitting device independent of a threshold voltage of a drive transistor connected in series to the organic light emitting device, the pixel circuit further including a discharge transistor connected between the organic light emitting device and a node of the pixel circuit, the method comprising: adjusting during a programming cycle a controllable voltage supply to a compensation voltage sufficient to turn off the organic light emitting device; in a first operating cycle of the programming cycle, selecting a select line, to turn on a selection transistor coupled to the drive transistor, for applying a reference voltage to the drive transistor through the selection transistor; in the first operating cycle, applying to a data line connected to the selection transistor a voltage that exceeds a programming voltage to be applied to the drive transistor; responsive to the adjusting, allowing the node of the pixel circuit to charge or discharge through the drive transistor, via the discharge transistor, until the drive transistor turns off, thereby establishing the threshold voltage of the drive transistor across the drive transistor; and in a further operating cycle of the programming cycle following the first operating cycle, selecting the select line to turn on the selection transistor for applying a programming voltage from the data line to the drive transistor through the selection transistor, thereby establishing a fixed voltage applied to the drive transistor according to both the threshold voltage and the applied programming voltage, wherein the programming voltage is lower than the reference voltage.