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I want to implement a driver circuit for piezo actuators for a positioning system. For this, I require a high-voltage, low-current output, similar to the one discussed here which features a circuit taken from here.

Concerning that circuit, I don't see how it can be used for a positioning system...The piezo elements can be "extended" and "contracted" by applying a higher and lower voltage across it, respectively. Where does this voltage control across the piezo happen in the circuit?

What I (ideally) want for myself is a way to supply the piezo with 0VDC to 75VDC depending on an analog DC input signal between 0V and 5V (from an IO-card).

EDIT: I don't know exactly which piezo was intended for the above circuit, however, my piezos are the PK2FMP1 from Thorlabs

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  • \$\begingroup\$ "I don't see how it can be used for a positioning system." Can you post the details / datasheet of the piezo actuator also ? The actuator may be driven by pulses, like a stepper motor would be controlled by number of pulses rather than the specific amplitude of each pulse. \$\endgroup\$ Commented Jul 8, 2020 at 13:13
  • \$\begingroup\$ @AJN, please see the edit. Thanks. \$\endgroup\$ Commented Jul 8, 2020 at 13:27
  • \$\begingroup\$ A piezo is a capacitor, and i=C*dV/dt, thus you need to know the max frequency and amplitude, or the maximum slew rate you want to use and calculate the maximum required current. This is very important to properly size the amplifier. For example if you want a 1kHz 75Vpp sine into your 4.2µF piezo that's a peak current of 2 Amps. And 75V is a high enough voltage worry about transistor safe operating area. \$\endgroup\$ Commented Jul 8, 2020 at 16:49
  • \$\begingroup\$ @peufeu I don't want anything oscillating, everything is DC. Unless I fundamentally misunderstood how piezos can be used... \$\endgroup\$ Commented Jul 8, 2020 at 16:55
  • \$\begingroup\$ Well if you use a piezo to move something back and forth, like moving the sensor in a tunnel microscope, then it's not DC, rather sawtooths. But if you want DC or very low frequency then it'll be easier, as the amplifier will only have to output current when the actuator moves. \$\endgroup\$ Commented Jul 8, 2020 at 17:07

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Here is a way to do this, using a couple high voltage transistors and an opamp.

  • The opamp provides precision gain, and allows input-output transfer function down to ZERO input volts.

  • The first transistor, with base driven from the opamp, is a high voltage NPN, with 2.2Kohm from base to ground, and a 1Kohm in the emitter to ground. The collector connects to the 2nd transistor's base.

  • The 2nd transistor operates up at 80+ volts, so we have some headroom for precision 75volt output.

  • The 2nd transistor is a high voltage PNP, with 2.2Kohm from base to +80 volts, and a 1Kohm from emitter to +80 volts. The collector is the high voltage, low current output node. We also use the collector in a feedback path.

  • Now we implement FEEDBACK for the precision behavior. Connect a 74,000 ohm resistor from collector of the PNP, to emitter of the NPN.

  • You now have current_mode feedback discrete circuit, with rather fast loop behavior.

  • What to do with the opamp, so we can remove the error introduced by the NPN's Vbe of 0.5 -- 0.7 volts?

Let me think about this for a while.

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