PURPOSE: To automatically change-over printing energy applying simultaneously with the change-over of a mode, by providing a pulse generating circuit for generating two kinds of printing pulses different corresponding to a printing mode while providing a pulse amplitude minute adjustment circuit.

CONSTITUTION: A printing pulse generating circuit is constituted of a clock pulse generating circuit 2 and a pulse amplitude setting circuit and generates two kinds of printing pulses different corresponding to a printing mode. The amplitude of each pulse signal is set by a pulse amplitude setting loop 3 so as to obtain optimum printing energy to each mode. The integrated circuit LS123 of a pulse amplitude minute adjustment circuit 4 is a one-shot multiplier and current supply of Tr determined by R and C is performed only for a definite time. By manipulating R, the amplitude of the pulse signal generated from the printing pulse generating circuit can be subjected to minute adjustment further finely.