MULTI-LEVEL VOLTAGE ADJUSTMENT

An adjustable voltage supply (310) may have a plurality of levels of adjustment, such as a coarse select circuit (471) and a fine select circuit (473), to generate an adjustable voltage (e.g. Vout 364 of FIGS. 3 and 4) with fine resolution across a wide voltage range. In one embodiment, the adjustable voltage may be used as an adjustable read voltage to measure the threshold voltages of bitcells in a memory array (300). From the distribution of these threshold voltages, it is possible to determine the marginality of the bitcells with regard to the voltage which is required to read the bitcells. In one embodiment, the adjustable voltage supply (310) may also be used to provide an adjustable voltage to one or more integrated circuit pwells and/or nwells in order to apply electrical stress. An adjustable voltage supply (310) may be used in any desired context, not just memories.