| 摘要 |
<p>PURPOSE:To obtain printing of uniform density at all times by providing a plurality of heat generating resistors and a plurality of signal lines provided to be selectively cut to alter conditions for heating heat generating resistor in response to the grade of the resistance value of the resistor. CONSTITUTION:A print signal P is received from a controller 1, and a printing head 3 having a plurality of heat generating resistors D1-D7 is driven. Since a thermistor TM is connected to the base side terminal (d) of a transistor Tr3, the bias voltage Vd of the terminal (d) is altered in response to a peripheral temperature, a heat application voltage Ve for obtaining a suitable printing density is output to the emitter side of a current supply transistor Tr4, currents flowing to the resistors D1-D7 become substantially constant to print in a suitable density. Further, since resistors R2, R3 are connected in the grade to the terminal (d), signal lines L1, L2 are selectively cut at the grade of the resistance value of the head 3, the composite resistance of the bias resistor group of the transistor Tr3 is altered to change the bias voltage Vd of the terminal (d), thereby obtaining a suitable head application voltage Ve.</p> |
