Patent ID: 8692590

Claim:
A liquid injector comprising: an actuator for injecting a liquid; and a capacitive load drive circuit that generates a drive signal for driving the actuator, The capacitive load drive circuit that drives a capacitive load by applying a predetermined drive signal to the capacitive load having a capacitive component, the circuit comprising: a drive waveform signal output circuit that outputs a drive waveform signal as a reference for the drive signal in a form of a digital signal; an arithmetic circuit that generates an error signal by computing a difference between the drive waveform signal and a feedback signal generated using the drive signal; a modulator that generates a modulated signal by pulse modulation of the error signal; a digital power amplifier that generates an amplified digital signal by power amplification of the modified signal; an inductive element that connects the digital power amplifier and the capacitive load and applies the drive signal to the capacitive load; and a phase-lead compensator that negatively feeds back a signal obtained by phase-lead compensation of the drive signal to the arithmetic circuit as the feedback signal, wherein the phase-lead compensator suppresses gain near a resonance frequency of a resonator formed by the inductive element and the capacitive load in a range of 1.5 times to 5 times of gain of the power amplifier.