Patent ID: 7216960

Claim:
A printhead driving method of driving a printhead, using a printhead substrate having a plurality of printing elements, and driving elements which are arranged in correspondence with the plurality of printing elements, which switch and control driving of corresponding printing elements, and which are formed from MOS transistors, the printhead substrate comprising a common wiring line which commonly supplies power, and to which a plurality of simultaneously drivable printing elements out of the plurality of printing elements are connected, and a first pad which supplies power to the common wiring line, wherein each of the driving elements is an element for supplying a constant current to the corresponding printing element, the method comprising the steps of: driving a plurality of driving elements at a constant current when time-divisionally dividing a plurality of printing elements into a plurality of blocks and driving the plurality of printing elements; measuring a value of a resistance representative of resistance values of the plurality of printing elements arranged on the printhead substrate; setting a gate width of a MOS transistor when driving one printing element, reflecting the resistance value measured in said measuring step; and controlling to operate the MOS transistor in a saturation region by applying a voltage to the printing element on the basis of a setting condition.