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measuring Ro by both Load and Drive methods

measuring Ro by both Load and Drive methods

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Jorge Rive
Posted by
on Apr 30 2012 13:45 PM
Prodigy40 points

Following Tim Green's article  in Operational Amplifier Stability, part 3 of 15, I simulated an OPA364 on LTSPICE.  The resulting Ro value is 152ohms vs. the 109 ohms that he gets in his article.  Could the Tina spice model be different than the Pspice model?  I noticed that the pspice model is dated 2004, while Tina's is 2009.  Could this be the source of the difference?

Thank you

TINA drive method load method pspice Ro
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  • Collin Wells
    Posted by
    on Apr 30 2012 15:25 PM
    Genius15510 points

    Hello Jorge,

    I looked at the TINA model and although it was reloaded to the internet in 2009, it appears to be the same 2003 model used for the PSPICE version.  I tested the model and here is the Zo curve that I received.  I found a value of 107 Ohms which closely matches Tim's results of 109 Ohms.

    There were some updates to Tim's testing methods for Zo that may not have been published.  Backdriving the amplifier is the preferred choice to test Zo in SPICE.

    Best Regards,
    Collin Wells
    Precision Linear Applications

     

    Regards,
    Collin Wells
    Precision Linear Applications

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