A 6T2C Pixel Circuit Compensating for TFT Electrical Characteristics Variations, Voltage Drop, and OLED Degradation

A voltage-programmed pixel circuit is presented for active-matrix organic light-emitting diode (AMOLED) displays. The circuit is made up by six p-type low temperature poly-silicon (LTPS) thin-film transistors (TFTs) and two capacitors (6T2C). In the extraction stage, the circuit extracts the driving TFT's threshold voltage and the power supply voltage. In the data input stage, the circuit generates a charging voltage, which is associated with the driving TFT's mobility and OLED's threshold voltage. Consequently, the pixel circuit not only compensates for the TFT's electrical characteristics variations, i.e., the threshold voltage and mobility variations, but also compensates for the voltage drop and the OLED degradation. The circuit simulation results show that the OLED current error rates (CERs) are lower than 7.13% when the threshold voltage varies ±0.5V, lower than 4.89% when the mobility varies ±30%, and lower than 8.92% when the voltage drop varies −0.5V.