Patent ID: 7234788

Claim:
A method to control a response of a droplet ejection device comprising a plurality of switches and a piezoelectric actuator, the method comprising: connecting the plurality of switches in parallel, each of the plurality of switches having a resistance; connecting the plurality of switches to the piezoelectric actuator having a capacitance, arranging the resistance from each of the plurality of switches and the capacitance of the piezoelectric actuator to form a low-pass filter circuit; and each switch comprises an input terminal to connect to a waveform signal, an output terminal to connect to the piezoelectric actuator, a control signal terminal to control a connection of the switch with a control signal, and a resistance between the input terminal and output terminal; selecting from a waveform table a waveform signal to apply to the input terminal of each of the plurality of switches the waveform signal comprising any of a step pulse, a sawtooth waveform, and a combination of two or more waveform patterns; applying the selected waveform signal on the input terminal of each of the plurality of switches, wherein each of the plurality of switches are connected at a common output terminal at the piezoelectric actuator; controlling the control signal terminal of each switch with the control signal; filtering high-frequency harmonics with the low-pass filter circuit to provide firing waveforms at the actuator that are consistent for a same pattern of input waveform signal; controlling the control signal terminal of each of the one or more of the switches of the low-pass filter circuit to form an effective resistance, Reff, for the low-pass circuit that is based on one or more resistors connected in parallel, wherein the effective resistance comprises a parallel combination of switches that are active in the low-pass filter circuit, wherein an active switch comprises a switch with a high voltage on the control signal terminal of the switch and the switch is electrically connected.