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TINA/Spice/THS3491: THS3491 TINA model name is misspelled

Michael Steffes
Guru 48165 points
Part Number: THS3491
Other Parts Discussed in Thread: TINA-TI, , THS4541, OPA837

Tool/software: TINA-TI or Spice Models

Good morning 

Sadly, my email server appears to be down - normally I would just email this to the right person (Hermann or John). But, instead

I notice again the Model name for the THS3491 shows instead "THD3491" . Easy to miss that with the focus on Total Harmonic Distortion (THD). 

However, the part and model should be THS3491. Easy to fix I would think. 

  • 0
    Guru 48165 points
    got into to contact with modeling via email, will get fixed
  • 0 in reply to Jacob Freet
    Guru 48165 points
    You bet Jacob, on that other topic of MFB filter design,

    Yes, that early app note I did had the cubic coefficients when you include the the op amp gain bandwidth incorrect -

    www.ti.com/.../sboa114.pdf

    I had fixed that in building the online Intersil (now Renesas) active filter design flows and published in this planet analog article,

    www.planetanalog.com/author.asp

    I had used this improved flow for the design using the THS4541 in this TI Design,

    www.ti.com/.../TIDA-00799

    Over recent years, I improved the fit algorithms and updated this design in this article,

    www.planetanalog.com/author.asp

    One of my recent changes was to increase the target for the minimum LG to 18dB from 12dB. The Gain Bandwidth margin question most rationally is a min LG target question. Around Fo, the LG finds a minimum where gain error, and more interesting, peak close loop output impedance occurs.

    Just using a high rule of thumb is less useful as the real issue is min LG. Then, to consider that outside the context of a reduced noise gain peaking RC solution flow is missing the point. I had been using an allowed 12dB min, but, with the emerging RR output devices with their higher open loop output impedance, showed that might be too low. In a burst of work Oct 2018, I did find some filters with 12dB min using the OPA837 where moving off match due to a peaking in the closed loop output impedance. So, rather than try to account for that (where the industrywide models for open loop output impedance are erratic at best), I moved my min target up to 18dB.