Dear Colleagues,

Good Day,

Try and see the attachments, please, they are very useful....

https://www.researchgate.net/post/Why_can_voltage_error_be_converted_to_current_using_a_PID_controller

https://www.allaboutcircuits.com/textbook/semiconductors/chpt-8/voltage-to-current-signal-conversion/

With a current driving power stage.

I mean, if you have a control system,

(1.) You have some error signal pickup, say position signal.

    - This can be either voltage or current. In optical disc, eg, error signal is derived

       from photocurrents, and they are currents.

   - The input signal is translated to voltage (if it was a current) with a transimpedance

     amplifier or something else.

(2.) You have a controller

   - Can be digital or analog. Nowadays more and more digital. Means

     input signal is converted by an A/D convertor to digital, control loop is

     executed in digital domain, output signal is converted to analog by means

     of an D/A convertor.

  - You can also do digital, integrated (I dont think this still exists), or with op-amps,

    or whatever.

(3.) You have an output stage.

   - Simplest form is class-B power amplifier, (take any power op-amp).

     Current drive means the op-amp senses the current through the actuator, and

    the feedback is such that the op-amp will equal the current to the input signal.

  - You can also have more complicated power stage, eg H-bridge PWM drive.

    This has higher efficiency, but I think this is most of the time voltage drive.

Best Regards,

Henri.