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OPA189: High speed Transimpedance Amp, 10V out

KB
Prodigy 160 points
Part Number: OPA189
Other Parts Discussed in Thread: OPA847, OPA828, OPA2156

I am looking for an amplifier that I can use for a TIA stage (~400 ohm gain) as well as a for a summing/difference stage and inverting stage that will satisfy the following requirements:

-Operation up to 500kHz

-Rail-to-rail input/output of 10V

-Very low voltage and current noise

-Unity gain stable

I initially planned to use the OPA189, but realized I can't hit my output voltage requirement at 500kHz.  Can you please point me in the direction of some options?  I can also use different amplifiers for the TIA stage and the subsequent stages.

  • 0
    Prodigy 160 points

    I was considering using the OPA847 for the TIA stage, since unity gain stability is not a requirement in that situation.  Photodiode capacitance will be between 10pF and 45pF depending on the reverse voltage we apply.  

  • 0 in reply to KB
    TI__Guru 54416 points

    HI KB,

    If I understood correctly, the application requires an output voltage of 10V, at 500-kHz, with the TIA configured with the 400Ω gain resistor.  The TIA needs to be able to source more than 25mA, and provide high enough slew-rate to support the large signal.  Is this correct?  

    For example, the OPA2156 (GBW = ~20MHz) is a rail-to -rail amplifier option that could work well, but there could be other possibilities depending on your requirements.  The OPA828 may be another option.  The OPA847 (3.9GHz) is a very high-speed amplifier. 

    In general the op-amp output voltage swing reduces with load output current. For example, the OPA2156 which offers rail-to-rail output will require >1V headroom from the rail while sourcing 25mA.  

    See below example supporting 10V signal while powered with a 12V supply rail and a small negative supply.  Let me know the maximum output swing that needs to be supported, the reverse diode voltage and the minimum and maximum current expected from the photosensor.

    Transient:

    Frequency response:

    Thank you and Regards,

    Luis