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THS4304 simulation model

Herman
Prodigy 20 points
Other Parts Discussed in Thread: THS4304, OPA846, OPA847

Have in Cadence OrCad 16.3 created a symbol for THS4304 and is using it together with the PSpice model to simulate a transconductance amplifier with 1k gain, e g 1k feedback resistor in parallel with 1pF. V+ is 5V and V- is 0V. Stimuli is a negative 1 mA current pulse with Tr=Tf=10ps and PW=20ns. The output voltage swings between 1V and 1.035V instead of  between 0V and ~1V. The downloadable OrCad symbol behaves strange when entered in Schematics and has two outputs (as D and DGK packages) while the simulation model has one. Therefore I am using my own.

  • 0
    TI__Expert 4625 points

    Hello Herman,

    When operating with a 5V single supply, the THS4304 has an output voltage swing of roughly 1V to 4V (depending on load conditions).  Therefore, with your current set-up, you won't be able to achieve a voltage swing between 0V and 1V.

    Using a different amp with bipolar supplies will allow you to get that output voltage swing.  I can help you select one--what is your approximate bandwidth requirement?

     

    Regards,

    Nick

  • 0 in reply to Nick
    TI__Expert 4625 points

    Correction: it is possible to run the THS4304 with +/-2.5V supplies.  This should give you an output signal swing of roughly -1.5V to 1.5V

     

    Regards,

    Nick

  • 0 in reply to Nick
    Prodigy 20 points

    Operating from +/-2.5V simulates properly although the amp is specified to be a single-supply device. For output voltage swing, I should have read the data sheet better. A swing from 1 (!) to 4V with high R load is quite unusual for a ss amp powered from 5V. Recommendations for another very fast (>1 GHz BW) amplifier is welcome provided the Iq is lower.

  • 0 in reply to Herman
    TI__Expert 4625 points

    Hi Herman,

    Other high bandwidth options for your transimpedance set-up are the OPA846 (1750MHz GBW, ~13mA Iq), and the OPA847 (3900MHz GBW, ~18mA Iq).

    As far as signal swing goes, you will have to use a bipolar supply set-up to get a 0V to 1V output in a single stage.  Some op amps have a rail-to-rail output that allow the output to get close to GND in a single supply configuration, but these do not have bandwidths high enough for your application.

     

    Regards,

    Nick