A voltage generator formed of a charge circuit and a discharge circuit having a common programmable voltage divider with variable resistance; the programmable voltage divider including a plurality of resistors arranged in series and selectively connectable to define alternatively a step-wise increasing program voltage and a fixed verify voltage. The charge circuit formed of a voltage regulator supplying at the output the precise voltage value determined by the programmable voltage divider, and the discharge circuit intervening when the output voltage must be switched in a controlled manner from a higher value to a lower value.