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TINA/Spice/OPA549-HIREL: Composite amplifier for OPA549-HiRel using OPA192 with improved DC accuracy and drift

Benyuan Liu
Intellectual 645 points
Part Number: OPA549-HIREL
Other Parts Discussed in Thread: TINA-TI, , OPA192, OPA549, THS3491, OPA191, OPA211, LM3886, OPA210, OPA548

Tool/software: TINA-TI or Spice Models

Hi, I want to build a composite amplifier using OPA192 + OPA549-HiRel with improved dc accuracy and drift performance. Could you please help me with this circuit? I build one using TI-Tina, but there are simulation convergence errors, I also do not know whether it can improve the dc and temperature drift performances or not.

opa549_composite.tsc

  • 0 in reply to Benyuan Liu
    Guru 140200 points
    Hi Byliu,

    don't rely too much on these simulations. Build the circuit up and test it with real loads!! This will change everything, believe me. And who says that the small signal overshots are relevant for you at all? The inductance of motor can absorb them, eventually. But check it with real world meadsurements and not with questionable simulations.

    Doing simulations is only the starting point of a development. They can be helpful but they also can give meaningless results. I have got uncountable bloody noses with doing simulations in my carrer. The simulation can give you tipps of what to do to cure an erosion of phase margin, for instance by introducing a phase lead capacitance here and there or by introducing a voltage divider. But only the measurement can tell you what is really going on.

    One measurement is worth a hundred simulations!

    Kai
  • 0 in reply to kai klaas69
    Guru 48395 points
    How true Kai,

    However, the product group owns the efficacy of the models vs Device - yes, their simple measurement in the lab would go a long ways to setting a direction - I don't think you want to use a device with a crossover deadzone in a composite circuit no matter what - if you can avoid it.
  • 0 in reply to kai klaas69
    Intellectual 645 points

    Dear Kai, Michael,

    Thank you for your help. I am going to build one, but the simulation results do affect my design scheme. It would be much better if TI could officially test and verify it.

    Originally I want to design a composite high current driver with high voltage monitoring and shunt current monitoring, plus position detector and a diode driver in one carrier card. Now I will build them separately with two small carriers connected by a wired connector. For the OPA549 part, I would design a bare OPA549 circuit (without composite first stage OPA192).

    Luckily, OPA549 was used in our country for some HiFi audio amplifiers (I do not know whether the crossover does affect the Hi-Fi quality :), I ordered one (cost 40$). I will share you with the results once I got it home. Although there are some tweaks needed, for example, remove DC blocking capacitors at the input and output.)

    Benyuan