Abstract: The OLED voltage of a selected pixel is extracted from the pixel produced when the pixel is programmed so that the pixel current is a function of the OLED voltage. One method for extracting the OLED voltage is to first program the pixel in a way that the current is not a function of OLED voltage, and then in a way that the current is a function of OLED voltage. During the latter stage, the programming voltage is changed so that the pixel current is the same as the pixel current when the pixel was programmed in a way that the current was not a function of OLED voltage. The difference in the two programming voltages is then used to extract the OLED voltage.