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hydrophone fully differential amplifier (differential input, differential output)

Traian Stanescu
Prodigy 90 points
Other Parts Discussed in Thread: OPA838, THS4551

Can anyone help with a reference design for a fully differential amplifier for a hydrophone (piezoceramic element)? It need to be differential input and differential output as signal needs to be transmitted over long lines. Thank you

  • 0
    Guru 140200 points
    Hi Traian,

    can say more about the sensor? Do you have a datasheet of at least an equivalent circuit model? And what about the input signals which have to be amplified? Any specification?

    Hhm, is a differential input stage actually needed? If so, why?

    Kai
  • 0 in reply to kai klaas69
    Guru 48395 points
    Hello Traian,

    If the sensor needs to see a high input impedance, consider the diff. I/O circuit in section 9.1.5 in the OPA838 datasheet where I also included a discussion of CM stability issues - we had a similar application using this where the next stage was an FDA like the THS4551. In that complete signal chain, the high output CM noise from this first stage was rejected by the CM loop of the FDA - pretty cool actually.

    If the sensor can see some R loading, consider just the FDA families directly.
  • 0 in reply to Michael Steffes
    Guru 48395 points
    And actually Traian, as I am recalling some ealier hydrophone work, it is sometimes the case they drive into a tuned network for narrowband gain. That would easier with the OPA838 approach where you still need to provide for input bias current to the V+ nodes.