7.2.1.1 Design Requirements

The OPAx596 is used to drive a piezoelectric actuator with a 100V operating range at a frequency of 100Hz. The

large capacitance inherent to the piezoelectric actuator can cause undesired ringing of the driver amplifier. An

inaccurate response of the actuator is possible due in part to amplifier instability. Adequate phase margin for a

500nF equivalent load is necessary for a robust driver circuit for the piezoelectric actuator presented here.

Table 7-1. Design Parameters

PARAMETER

VALUE

Positive supply voltage

60V

Negative supply voltage

–5V

Piezoelectric actuator capacitance (1kHz)

500nF

Piezoelectric operating voltage range

0V to 100V

Operating frequency

100Hz

DAC output voltage

5VPP

7.2.1.2 Detailed Design Procedure

Piezoelectric actuators offer many benefits over traditional solenoid counterparts. Piezoelectric actuators are

more precise, power efficient, and smaller in general when compared to solenoid actuators. One challenge

with piezoelectric actuators is that the piezoelectric actuators operate over a very wide voltage range. Driving

voltages of more than 60V are not uncommon, and can easily reach hundreds of volts. The OPAx596 operate

with a supply voltage of up to 85V.

In this design example, the OPAx596 are used to provide a 100VPP signal to control a high-voltage piezoelectric

actuator (see also Figure 7-1). The piezoelectric actuator can be modeled as a large capacitor when operated at

less than the resonant frequency. The piezoelectric actuator is treated as a floating load driven by two op amps

of the OPAx596. The outputs of the op amps are set to be 180° out-of-phase to essentially double the voltage

seen by the actuator load.

The signal voltage of the digital-to-analog converter is applied a 10V/V gain by the OPAx596. A simple voltage

divider provides a 2.5V reference to level shift the output to create a unipolar driving voltage. An isolation resistor

improves phase margin and stability. Add a small 10Ω RISO at the output of the OPAx596.

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OPA596

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