OPA683: OPA683 versus OPA684 input offset voltage in TINA models

Prodigy 100 points

Replies: 12

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Part Number: OPA683

I have been doing some TINA spice simulations with both the OPA683 and OPA684.

The non-inverting input is connected to ground, and the inverting input is connected to a small signal input and has a gain of 40 (1K ohm feedback resistor, and a 25 ohm resister connected to small signal source).

Both the OPA683 and OPA684 list a typical input offset voltage at +/- 1.5 mV.

However performing a TINA spice simulation produces a -0.1mV input offset for the OPA684 and an 2.5mV input offset for the OPA683.

I am curious if this is just model differences / inaccuracies, or if there are actual difference in these two opamps which would result in these varying offsets for my circuit?

12 Replies

  • In reply to Michael Steffes:

    Thanks for your help Michael.

    The problem seems to be in TI TINA spice model.

    I have been using the OPA683 under the Spice Macros tab of Tina SPICE (which yields the 2.21mv offset)
    when I swap the spice macro OPA683 with the OPA683 from the reference design, I get an offset of 162uV.
    when I delete the ref design OPA683 and try to replace it with the Spice Macro OPAMP OPA683,  and then run DC Analysis, I get the following error:

    "Missing syntax element.Line #1.(OPA683).

    This suggests the spice model for the OPA683 under the SPICE Macros OP AMP menu is incorrect or has issues!?!?

    Now not sure what to trust on any of my previous simulations.

  • In reply to Chris Roden:

    Hey Chris, 

    If you right click on the symbol, a menu will open where at the bottom is an enter macro to see the netlisting. To get out of that in the upper left hand is a close icon, 

    Anyway, I don't think DesignSoft updates their library very much (if at all) the TINA library model is 2002 original - 

    The product landing page model is a 2011 update, I always suggest to use the latest on the product folder - those get updated kind of randomly. This was using a 2008 revised datasheet. 

    Michael Steffes