An a-IGZO TFTs integrated gate driver with programmable output waveform for AMOLED display is proposed by shared input shift registers and output stages of multiple clock-follower structure. The driver provides not only multiple scan and control signals for internal compensation, but also extended scan pulses for external compensation.
A new OLEDoS pixel circuit is proposed for high resolution micro-displays with improved image quality. The data voltage range is extended by using two coupling capacitors to raise the voltage at the source electrode of the driving transistor. Furthermore, the image quality is improved by a compensation scheme of the threshold voltage variation of the driving transistor. The simulations on the basis of CSMC 0.25 μm CMOS model are used to verify the performance of the proposed pixel circuit. It is shown that the data voltage of the proposed pixel circuit ranges from 1.5 V to 3.05 V, which is 2.5 times of that of the conventional 2T1C pixel circuit. The emission current error is decreased to -2.6% ~ 2.6% with ±5 mV threshold voltage variation of the driving transistor for the proposed circuit.
External compensation is an effective scheme to adapt the threshold voltage variations of the driving Thin-Film Transistors (TFTs) and the deterioration of the Organic Light-Emitting Diodes (OLEDs) in pixel circuits of Active-Matrix Organic Light-Emitting Diode (AMOLED) display systems. In this paper, an accurate current comparator is proposed to sense the difference between the current trickling through the OLED and the reference current, so that the deterioration and variations of TFTs and OLEDs in the AMOLED pixel circuits can be detected and compensated effectively. The proposed current comparator is demonstrated in a source driver chip for AMOLED panel with external compensation and fabricated in a 0.25-μm high-voltage CMOS technology. The sensing accuracy of the proposed current comparator is less than 5.3 nA by chip measurement with 500 nA reference current. Furthermore, the sensing error of the proposed current comparator is lower than 1.05%.
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