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TINA/Spice/OPA171: TINA-TI simulation differs from WEBENCH simulation

Part Number: OPA171
Other Parts Discussed in Thread: TINA-TI,

Tool/software: TINA-TI or Spice Models

I have a problem with simulation of an inverting amplifier using the OPA171.

Link to WEBENCH design: https://webench.ti.com/appinfo/webench/scripts/SDP.cgi?ID=A3ACA35C5738CF78

This is an image of the same simulation inside TINA-TI:

Here are the TINA-TI files:
OPA171.TSM

output.TSC

The OPA171 TSC is the official spice model from ti.com.

The WEBENCH simulation gives the expected result, but the TINA-TI simulation does not.
Am I missing something obvious?

Hope you can help me :-)

  • Hi Rune,

    Could you attached your .TSC to this post?

    Also can you describe to us what's wrong with the simulation result on TINA-TI? Do you think it's wrong in term of DC operating point? Transient simulation does not give you the correct gain? etc etc.

    Sorry I am not 100% clear from the picture you attached, so if you can attach your .TSC as well as giving more explanation, it will be helpful.

    Herman
  • Thanks for taking a look Herman!

    I have updated the post with the files you requested.
    What I'm experiencing is a difference in the transient and DC nodal voltage simulation.
    In WEBENCH the transient output of a 1kHz 0-2.5V sinusoidal signal is ~+-5V (as expected from the design).
    In TINA-TI the same design gives a transient result of -2.43V to 4.92V.

    I would expect TINA-TI to give the exact same result as WEBENCH.

    I'm new to simulation, so there might be something obvious I'm overlooking ;-)

  • Hi Rune,

    To get +/-5 V as shown in webench, we need to follow webench's schematic where you put the voltage generator at the positive terminal of the amplifier rather than on the left side of the resistor as shown in your schematic.

    Also you need to shift your dc voltages at the input from 1.25V to 0V. If you decide to still put 1.25V, then your output will +/-5V + 1.25 DC output offset which translates to 6.25V to - 3.75V swing.

    Attached is your TSC test bench with modification as I explained. 0385.output.TSC

    Herman

  • I'm so sorry Herman. In my confusion I didn't even realize that the WEBBENCH simulated a non-inverting amplifier.
    Thank you for pointing it out to me, and sorry for wasting your time on this :-)