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Ultra low Noise Power Amplifier Circuit for driving Voice Coil Motor

Gaurav Parmar
Prodigy 20 points
Other Parts Discussed in Thread: OPA569, LM3886

Application: We are making a long range nanopositioning system with range 10mm and resolution 10nm. The mechanism is actuated by voice coil motor which needs a driver. The driver has to deliver high current (for range) with ultra low noise and distortion (for resolution).

Specifications for amplifier circuit:
1. Max current : 10A
2. Bandwidth : 200Hz
3. Noise Floor : -110dB
4. Total harmonic Distortion > 100dB

Q) Is it possible to design an power amplifier circuit with such noise specifications?

Q) Is there any reference circuit for low noise and distortion which I can look at?

Q) Which is the best power op amp for high output current and low noise and distortion?

  • 0
    TI__Expert 7185 points

    Gaurav,

    You might consider using 5 OPA569 devices in parallel to accomplish this task.  For more information on parallel operation of the OPA569 see figure 14 on page 18 of the data sheet.

    Matt

  • 0 in reply to Matthew Hann
    Prodigy 250 points

    You could also use (excuse me) a driver from National LME49810/49830 and some power transistors.

    http://www.national.com/pf/LM/LME49810.html

    http://www.national.com/pf/LM/LME49830.html

    Dist 0.007%, current = pretty much

    When I see the specs I suspect that they may be exaggerated a bit because I have personal experience from this. It's normal that you have made calculations but you may not be aware of the real world but I'm pretty convinced that some power opamp, maybe in parallel will do or the IC's I mention or perhaps LM3886 which can deliver short term over 10 A.

    You don't mention anything about the needed output voltage? LME49810 can handle 200 V supply voltage, LM3886 92 V and OPA569 only 7.5V but if the need output voltage is low the OPA569 might work. It sure is a compact solution.