An OLED (organic light-emitting diode) passive-matrix display includes a display portion and a driver portion. The display portion includes a matrix of OLEDs for displaying information. The driver portion includes a monitor circuit and a voltage adjusting circuit. The voltage adjusting circuit has a power-up portion that generates a supply voltage based on a reference voltage. In response to an indication to switch modes, the voltage adjusting circuit switches to an operational mode wherein the supply voltage is generated based on the maximum voltage drop read across the OLEDs.