Patent US 5,608,669

A method for storing a charge on memory devices which includes the steps of providing a first charging pulse to a memory device to charge the device to a first level less than a final level; testing the value of the charge to determine whether the charge is greater than the first level; if the value of the charge is less than the first level, providing a second set of charging pulses to the memory device, each of the pulses of the second set of pulses having a duration which is a fraction of the duration of the first pulse and a value sufficient to charge the device to the first level; testing the value of the charge to determine whether the charge is greater than the first level after each pulse of the second set of pulses; and once the charge has tested greater than the first level, providing a third set of charging pulses to terminals of the memory device, each of the pulses of the third set of pulses having a duration which is a fraction of the duration of the pulses of the second set of pulses and a value such that the charge furnished by each pulse is approximately equal to an allowable variation of the charge from the final value.