Patent ID: 7494202

Claim:
An image forming apparatus, comprising: a print head that includes a plurality of driving elements for printing dots along main lines and sub-lines between the main lines, the driving elements being disposed in a row, and the main lines and sub-lines being disposed parallel to the row, a shifting section for shifting print data into the print head, a latching section for latching the shifted-in print data, and an actuating section, responsive to a strobe signal and a reference voltage, for actuating the driving elements in accordance with the print data latched by the latching section and for setting the magnitude of current supplied to the driving elements in accordance with the reference voltage, the actuating section including a plurality of actuating circuits, each of which is connected to a respective one of the driving elements; and a control section for controlling the reference voltage so that the current supplied to the driving elements is higher in magnitude when the driving elements print dots along the main lines than when the driving elements print dots along the sub-lines, wherein not more than three sub-lines are present between consecutive main lines, and wherein each of the actuating circuits comprises a transistor having a source, drain, and gate, the source of the transistor receiving a drive voltage and the drain of the transistor being connected to the respective one of the driving elements, a gate circuit having a first input terminal that is connected to the latching section and a second input terminal that receives the strobe signal, and a current varying circuit that receives an output signal of the gate circuit and the reference voltage, the current varying circuit having an output terminal that is connected to the gate of the transistor, the transistor and the current varying circuit cooperating to form a current mirror circuit that outputs a drive current to the respective one of the driving elements based on the reference voltage, the drive current being output to the respective one of the transistors during a period determined by the output signal of the gate circuit.