Patent ID: 8240798

Claim:
A head drive apparatus of an inkjet printer, the head drive apparatus comprising: a plurality of nozzles that jet a plurality of liquid drops from an inkjet head; a plurality of actuators provided in correspondence to the nozzles; and a drive unit that applies a drive signal to the actuators, wherein the head drive apparatus includes: a drive waveform generator that generates a drive waveform signal which is used as a reference of a signal to control driving of the actuators; a modulator that modulates a pulse of a drive waveform signal generated by the drive waveform generator; a digital power amplifier that amplifies power of a modulated signal subjected to the pulse modulation by the modulator; a low pass filter that smoothes an amplified digital signal subjected to the power amplification by the digital power amplifier and supplies the signal as the drive signal to the actuators; and a control unit that determines a number of the actuators to be driven by the drive signal and adjusts frequency characteristics of the low pass filter as a function of the number of the actuators to be driven before the drive signal is supplied to the actuators, wherein the control unit adjusts the frequency characteristics by changing a capacitance of the low pass filter.