Signal processing apparatus, droplet ejection apparatus and signal processing method

A droplet ejection apparatus comprising:

• a droplet ejection head comprising nozzles, the nozzles each ejecting a droplet by a piezoelectric element being driven;
• a head controller that controls the droplet ejection head so as to eject the droplets from the nozzles on a recording medium based on image information;
• and
• a signal processing apparatus comprising:
• a first circuit board comprising a digital/analog converter which converts, to an analog signal, a digital signal as a reference of a voltage to be applied to a capacitive load and outputs the analog signal, the capacitive load being the piezoelectric element;
• a second circuit board comprising an operational amplifier connected to the capacitive load at an output terminal thereof via a switching element, that amplifies the voltage of the analog signal and outputs the analog signal;
• a connector that mechanically connects the first circuit board and the second circuit board such that the analog signal output from the digital/analog converter is input to an input terminal of the operational amplifier;
• a transmitter provided in the first circuit board that transmits a predetermined signal to the second circuit board via the connector;
• and
• a controller that, when the predetermined signal is not received in the second circuit board, prevents the voltage of the analog signal from being applied to the capacitive load via the switching element.