Design of a voltage-programmed V TH compensating pixel circuit for AMOLED displays using diode-connected a-IGZO TFT
This study presents a novel voltage-programmed, amorphous-indium–gallium–zinc oxide (a-IGZO) thin-film transistor (TFT)-based active-matrix organic light-emitting diode (AMOLED) pixel circuit. The circuit utilises the threshold voltage (V TH) sensing ability of a diode-connected transistor to compensate for the spatial as well as the temporal variation of the threshold voltage of the driving transistor and supply a constant current to the OLED. The circuit has been simulated in Cadence Spectre using a-IGZO TFT and OLED simulation program with integrated circuit emphasis (SPICE) models, and the analysis is presented to prove the V TH compensating capability of the proposed circuit. For small currents, about 50 nA, the error is suppressed to <9% whereas for large currents, about 2.5 µA, the error is only 1.05%. This performance has been achieved using only five TFTs and two storage capacitors.