Patent ID: 8130182

Claim:
A method of compensating for variations in characteristics of an electroluminescent (EL) emitter in an EL subpixel, comprising: (a) providing the EL subpixel having a drive transistor, the EL emitter, and a readout transistor, wherein each of the drive transistor and the readout transistor has a first electrode, a second electrode, and a gate electrode; (b) providing a first voltage source and a first switch for selectively connecting the first voltage source to the first electrode of the drive transistor; (c) connecting the EL emitter to the second electrode of the drive transistor; (d) providing a second voltage source connected to the EL emitter; (e) connecting the first electrode of the readout transistor to the second electrode of the drive transistor; (f) providing a current source and a third switch for selectively connecting the current source to the second electrode of the readout transistor, wherein the current source provides a selected test current to the EL emitter; (g) providing a voltage measurement circuit connected to the second electrode of the readout transistor; (h) opening the first switch, closing the third switch, measuring the voltage at the second electrode of the readout transistor by the voltage measurement circuit at least two times, and providing a first emitter-voltage signal in response to the at least two measurements; (i) using the first emitter-voltage signal to provide an aging signal representative of characteristics of the EL emitter; (j) receiving an input signal; (k) using the aging signal and the input signal to produce a compensated drive signal; and (l) providing a selected drive voltage to the gate electrode of the drive transistor for a selected on-time corresponding to the compensated drive signal, wherein the selected drive voltage causes the drive transistor to operate in a linear region during the selected on-time, to compensate for variations in characteristics of the EL emitter.