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Searching for a charge amplifier design

Edwin Krasser
Expert 2410 points
Other Parts Discussed in Thread: OPA2348, OPA656

Hello!

I am searching for a charge amplifier design. The input current/charge is delivered by a piezo element with one pin connected to ground (because of the mechanical design), so it's single ended. Now we want to build a charge amplifier for feeding a high speed adc (input voltage range: 0-3 V) that has got differential inputs. It's rather easy to build this single ended to differential conversion with two voltage feedback opamps (that's the current development state).

Does anybody know a design which is able to do this with just one (!) differential opamp?

Best regards,
Edwin Krasser

  • 0
    TI__Expert 4115 points

    Edwin,

    In theory, inverting op amp topologies can be converted to use with a fully differential op amp, and a charge amplifier is an inverting op amp topology. However, in practice you need a very high input impedance amplifier like a FET device to make the circuit work right, and I do not know of any high input impedance FDAs on the market today.

    It is probably more practical to look at making a differential charge amplifier using 2 standard op amps. For lower frequency applications, I would look at CMOS input op amps like the OPA2348. For higher frequency, I would look at JFET input op amps like the OPA656.