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We present a digital calibration driving scheme for stabilizing the uniformity of large area amorphous silicon active-matrix organic light emitting diode displays. A current-mode analog-to-digital converter (ADC) is used to extract the differential aging of the individual pixels. For the ADC, a configurable current comparator is designed that employs the output buffer of the source driver to reduce the die area. The comparator and pixel circuit were fabricated in 0.8-mum high-voltage CMOS and amorphous silicon technologies, respectively. Analysis and measurement results show a calibration refresh time of 2 s for a high-definition display (1920 times RGB times 1080). Moreover, the pixel current is highly stable despite a 5-V shift in the threshold voltage of the thin-film transistor driver.