Active-matrix organic light emitting diode (AMOLED) displays are attracting attention due to several key advantages such as high efficiency, wide viewing angle, high contrast, and low fabrication cost. Among different technologies for implementation of AMOLED pixel circuits, hydrogenated amorphous silicon (a-Si:H) thin film transistor (TFT) is gathering more attention due to well established manufacturing infrastructure and low fabrication cost. However the threshold voltage (VT) of a-Si:H TFTs shifts over time with gate bias stress. If the current in the pixels depends on the VT of TFTs, VT shift causes degradation in the OLED luminance. This signifies the demand for pixel circuits and driving schemes that provide the OLED with a VT-independent current. Among different driving schemes, current programming has shown reasonable stability (A. Nathan et al., “Amorphous silicon thin film transistor circuit integration for organic LED displays on glass and plastic,” IEEE J. Solid-State Circuits, vol. 39, no. 9, September 2004, pp. 1477-1486). However, for small currents the programming time is large due to low field-effect mobility of a-Si:H TFTs and high parasitic capacitance of the data line. VT-compensating voltage-programmed pixels have smaller programming times (J. Goh et al., “A new a-Si:H thin-film transistor pixel circuit for active-matrix organic light-emitting diodes,” IEEE Electron Dev. Letts., vol. 24, no. 9, pp. 583-585, 2003) at the cost of imperfect compensation of VT.
Recently, a driving scheme based on voltage feedback has been presented (S. Jafarabadiashtiani et al., “P-25: A New Driving Method for a-Si AMOLED Displays Based on Voltage Feedback,” Dig. of Tech. Papers, SID Int. Symp., Boston, pp. 316-319, May 27, 2005). The method provides proven stability and faster programming than the current-programming scheme. However, it is not fast enough to fulfill the demands for high-resolution large displays.
It is therefore desirable to provide a method and system that enhance the programming speed of a light emitting device display.