A virtual ground array based flash memory device includes a virtual ground array containing individual memory elements with supporting input/output circuitry. The threshold voltages of the memory elements gradually increase over operating cycles due to trapping of charge in the nitride or oxide, eventually causing errors due to the increase in threshold voltage. Internal routines are necessary to characterize the change in threshold voltages and subsequently modify the comparison circuit supplying the current used to determine whether the memory elements have attained a specific threshold. The method of automatically adjusting the window of the virtual ground array increases endurance and reliability of the virtual ground array and decreases errors caused by the increased threshold voltage.