Abstract: In some examples, a drive signal generator for a fluid ejection element of a piezoelectric printhead, includes a core amplifier to amplify an input waveform to provide an amplified waveform, and a plurality of rail power circuits, each coupled to a different power input of the core amplifier. Each rail power circuit of the plurality of rail power circuits includes a comparator to compare an instantaneous voltage of the amplified waveform to a subset of a plurality of voltage sources, and a switch to, based on the comparing by the comparator, couple to a respective power input of the core amplifier a voltage source in the subset of the plurality of voltage sources that is closest to the instantaneous voltage and sufficient to generate the amplified waveform.

Abstract: In an embodiment, a fluid level sensor includes a sensor plate and a current source. The fluid level sensor also includes an algorithm to bias the current source such that current applied to the sensor plate induces a maximum difference in response voltage between a dry sensor plate condition and a wet sensor plate condition.

Abstract: In some examples, a printing system comprises a plurality of microelectromechanical systems (MEMS) dies comprising printing fluid jets, a printhead assembly (PHA) application specific integrated circuit (ASIC), and a substrate comprising the plurality of MEMS dies and the PHA ASIC. The PHA ASIC is to process image data into a plurality of data signals that define a firing pattern, and transmit the data signals through transmission lines on the substrate to the plurality of MEMS dies. The printing fluid jets of the plurality of MEMS dies are to fire in response to the data signals.

Abstract: A microfluidic device can include: a channel; a fluid inlet to pass fluid into the channel from a reservoir; a sensor disposed in the channel; and a pump actuator disposed in the channel apart from the sensor to induce fluid flow into the channel.

Abstract: In some examples, a controller receives impedance sensor values from an impedance sensor in a printhead, determines whether the impedance sensor values correlate to a production of an effective drive bubble for the printhead, and issues a command to modify a firing parameter for a fluid ejector of the printhead based on the impedance sensor values.

Abstract: In some examples, a method of regulating a temperature of a printhead includes charging, in a first state of a temperature regulator, an analog memory to a reference voltage that corresponds to a predetermined temperature of the printhead. The temperature regulator monitors, during a second state, the temperature of the printhead, the monitoring including measuring a thermal voltage representing an actual temperature of at least a first local area of a plurality of local areas of the printhead, and comparing, with a comparator, the reference voltage to the thermal voltage to obtain a comparison result for at least the first local area. Based on the comparison result, a series of warming pulses from a warming pulse circuit to at least the first local area is selectively enabled.

Abstract: A printhead circuit for providing pulses for driving two or more actuating elements, the circuit comprising a cold switch drive circuit, for driving an actuating element for a first phase of a first pulse, the cold switch drive circuit having a cold drive switch for selectively coupling a drive waveform to the actuating element during the first phase according to a print signal; and a hot switch drive circuit, for driving the actuating element for a second phase of the first pulse, wherein the hot switch drive circuit is configured to drive the actuating element during the second phase according to an actuating element compensation indication signal.

Abstract: A print head assembly (PHA) includes a microelectromechanical systems (MEMS) die mounted to a substrate with an application specific integrated circuit (ASIC). The die includes an opening defined in the die, a plurality of nozzles adjacent to the opening in fluid communication with the opening, and a pad to receive electrical control signals. The ASIC includes a communication link and a plurality of transmission lines that transmit electrical signals to the MEMS die.

Abstract: In some examples, a printhead includes a firing chamber to receive printer fluid, an ejector positioned in the firing chamber to eject printer fluid droplets from the printhead, and a nozzle in fluid communication with the firing chamber. The printhead can further include an impedance sensor positioned in the firing chamber to contact printer fluid to measure impedance values of the printer fluid. The impedance sensor can be connectable to a controller to transmit impedance values of printer fluid to the controller.

Abstract: An apparatus including an analog memory, a temperature sensor, a comparator, and a pulse circuit. The analog memory is charged to a reference voltage corresponding to a predetermined temperature of a printhead. The temperature sensor measures a thermal voltage of at least one of the plurality of local areas of the printhead. The comparator obtains a comparison result by comparing the reference voltage to the thermal voltage. The pulse circuit selectively transmits a series of warming pulses to the at least one of the plurality of local areas of the printhead based on the comparison result.

Abstract: In some examples, a piezoelectric fluid ejection assembly includes a micro-electro mechanical system (MEMS) die including a plurality of nozzles, a first application-specific integrated circuit (ASIC) die electrically connected to the MEMS die, and a second ASIC die electrically connected to the MEMS die. The first ASIC die includes a plurality of driver amplifiers for respective nozzles of a first number of the plurality of nozzles, and a plurality of unique waveform data generators to generate respective different waveforms for activating the nozzles of the first number of the plurality of nozzles.

Abstract: In some examples, a piezoelectric printhead assembly can include a plurality of piezoelectric micro-electro mechanical system (MEMS) dies, and application-specific integrated circuit (ASIC) dies electrically connected to the piezoelectric MEMS dies.

Abstract: A printhead circuit or driving at least two actuating elements has a trim generating circuit for generating a trim signal using a comparator coupled to receive and compare feedback indicative of a present level of a drive voltage, with a configurable reference voltage value. The trim being based on a drive voltage feedback can give a more direct indication of actuating element output than given by timing references. Hence the trim can be more accurate, can be simpler, without accurate digital timing references, and thus costs can be reduced. It can be combined with a cold switch arrangement.

Abstract: A driver circuit for driving actuating elements for printing, has a switch for coupling a common drive signal to provide element drive pulses to drive each actuating element according to a print signal. A timing control circuit controls the switch during sloped transitions of the common drive signal, to trim an amplitude of the actuating element drive pulses according to a common offset configurable for at least two of the actuating elements in common, and according to an element specific offset, configurable for each of the actuating elements. The offsets can be dynamic or static, and some parts of the timing can be implemented in analog form. This enables more types of errors to be compensated, and can enable the element specific offset to be implemented with simpler circuitry with less heat dissipation or less space or needing less precision and thus less cost.

Abstract: In an embodiment, a fluid level sensor includes a sensor plate and a current source. The fluid level sensor also includes an algorithm to bias the current source such that current applied to the sensor plate induces a maximum difference in response voltage between a dry sensor plate condition and a wet sensor plate condition.

Abstract: Measuring an inkjet nozzle may include taking at least one impedance measurement after the firing command is sent to detect the presence of a drive bubble and taking another impedance measurement to detect a collapse of the drive bubble.

Abstract: An inkjet printing system, fluid ejection system and method thereof are disclosed. The fluid ejection system includes a fluid ejection device and a determination module to determine a supply condition based on the count value output by the converter module. The fluid ejection device includes a fluid supply chamber to store fluid, an ejection chamber including a nozzle and a corresponding ejection member to selectively eject the fluid through the nozzle, a pressure sensor unit having a sensor plate to output a voltage value corresponding to a cross-sectional area of an amount of fluid in the ejection chamber. The fluid ejection system also includes a converter module to output a count value corresponding to the voltage value output by the pressure sensor unit.

Abstract: Measuring an inkjet nozzle may include taking at least one impedance measurement after the firing command is sent to detect the presence of a drive bubble and taking another impedance measurement to detect a collapse of the drive bubble.

Abstract: In some examples, a drive signal generator for a fluid ejection element of a piezoelectric printhead, includes a core amplifier to amplify an input waveform to provide an amplified waveform, and a plurality of rail power circuits, each coupled to a different power input of the core amplifier. Each rail power circuit of the plurality of rail power circuits includes a comparator to compare an instantaneous voltage of the amplified waveform to a subset of a plurality of voltage sources, and a switch to, based on the comparing by the comparator, couple to a respective power input of the core amplifier a voltage source in the subset of the plurality of voltage sources that is closest to the instantaneous voltage and sufficient to generate the amplified waveform.

Abstract: In one example, a device for driving a nozzle of a fluid-jet printing device includes a circuit to, for each pixel time of a plurality of pixel times select a waveform from a plurality of waveforms based on more than one of waveform time delay, waveform pulse width and waveform shape, and apply the selected waveform to the nozzle to drive the nozzle to eject fluid for a current pixel time.