Abstract: An electronic circuit for driving an ink jet print head of the type wherein a droplet of ink is ejected from an ink chamber through an orifice upon demand by pulsing a piezoelectric element in a manner to suddenly reduce the volume of the chamber. Switching circuits responsive to a low level control signal cooperatively energize the piezoelectric element for the duration of a control pulse and discharge the inherent capacitance of the crystal at the end of the control pulse. A storage capacitor is connected in a way to reduce the current drain on the power supply. Critical semi-conductor switching elements are provided with variable biases to maximize their switching speed.

Abstract: An electronic circuit for sensing and controlling the pressure and temperature of ink within an ink jet print head. Ink pressure is monitored by a pair of strain gauges electrically connected into a bridge whose output controls an ink supply valve. Part of that bridge is utilized with additional elements to form a second bridge for monitoring through one of the strain gauges the temperature of the ink jet head, accompanied with a heater of the head that is driven from the temperature signal to maintain the head temperature above a preset temperature.