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About the harmonic distortion questions

Kailyn Chen
Genius 9560 points
Other Parts Discussed in Thread: OPA1612

Hello,

I have a question about the  Harmonic distortion with TINA,  take OPA1612 for example,  the Harmonic distortion  is 3.886% when using inverting input, while the harmonic distortion is 0.0002% when using non-inverting input. My personal understanding is opposite because the inverting input could not encounter input crossover distortion due to its Vcm doesn't change Vcm=0, so the Harmonic distortion of  inverting input should less than non-inverting input, but the results of TINA is opposite.

Best regards

Kailyn

  • 0
    Guru 48395 points

    Why are you taking the output as Vos - the inverting error voltage

    1. Should be looking at Vout

    2. might have a stability issue, check that and or remove the 50pF load

    3. The TINA op amp models do not usually include distortion features. 

  • 0
    TI__Genius 14320 points

    Hi Kailyn,

    THD is not a modeled specification for any of our recent op amp macromodels, so any THD results from a TINA simulation will be inaccurate.

    It is possible that the difference between these two simulations is due to loading effects in the inverting amplifier case - the inverting amplifier output has a load of 2kΩ to ground, whereas the inverting case has no resistive load to ground.