It’s important to follow sound principles with respect to any driving circuits used with these devices.
Over the past few decades, the use of piezoelectric actuators has seen a growing increase in popularity. This is due to the many advantages these devices offer, some of which are as follows:
- No moving parts: This makes motion in the sub-nanometer realm possible.
- Fast response: Microsecond response times with acceleration rates of more than 10,000g.
- High force generation: Capable of moving loads of several tons.
- No magnetic fields: Piezoelectric actuators produce no magnetic fields, nor are they affected by them.
- Low power consumption: Static operation consumes virtually no power.
- No wear: No moving parts such as gears or bearings.
- Vacuum and clean room compatible: Piezoelectric actuators cause no wear and do not require lubricants.
- Operate at cryogenic temperatures: The piezoelectric effect continues to operate at temperatures approaching zero degrees kelvin.
Using piezoelectric actuators can provide many benefits, but it is crucial to keep some essentials in mind when designing systems that employ these components.
Limited strength in tension: The tensile strength of a cylindrical piezoelectric actuator is approximately 10% of its strength in compression. It is essential to abide by these values to avoid fracturing the piezoelectric actuator. Specific values can be obtained from data sheets supplied by the piezoelectric actuator manufacturers.
Boundaries on acceleration: When driven by a periodic waveform, the acceleration will increase exponentially with frequency. So, it is important to identify the upper limit of the device’s ability to withstand high acceleration forces. In particular, multilayer piezoelectric actuators are vulnerable to delamination should their acceleration limits be exceeded.
Driver circuits do consume power: As was noted earlier, piezoelectric actuators consume virtually no power when static, other than the quiescent power consumed by the electronics. However, the power
dissipation demands from any power operational amplifier circuits when the actuator is driven can be significant indeed.
Follow sound principles
It’s important to follow sound principles (no pun intended) with respect to any driving circuits. Make sure the driving power operational amplifiers are operating in their safe operating region and current limiting is provided to protect the circuitry from an inadvertent short circuit. Other essential design tasks include selecting a satisfactory heatsink, flyback diodes and compensation capacitors.
Piezoelectric applications are commonly driven with higher voltages (typically greater than 50V). For this purpose, Apex Microtechnology offers high-performance power operational amplifiers ranging from 50V to 2500V. One such example is the PA98. This 450V, 200mA high-power operational amplifier with an impressive 1,000V/µs slew rate is targeted for high voltage applications including piezoelectric transducers, electrostatic transducers, and deflection.
The PA98 series is a hybrid product design housed in a space saving, electrically isolated 12-pin PowerSIP package, which lends itself to high-density circuit board layouts. Please visit our website to view our full product portfolio, including the PA98.