Abstract: An ink-jet printer comprises a piezoelectric element, a pressurization chamber coupled to the piezoelectric element for containing ink therein, and a nozzle communicating with the pressurization chamber, the piezoelectric element being deformable upon application of a drive voltage V to change the volume of the pressurization chamber for ejecting ink from the nozzle. The vibratory system including the piezoelectric element has an acoustic capacitance Co selected with respect to the flow passage system including said nozzle, said pressurization chamber and an ink supply passage, so as to minimize the drive voltage V. Drive voltage is related to the capacitance Co, electrical capacitance cp of the piezoelectric element and pressure .psi. as follows: ##EQU1## K is a constant.