This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

OPA1656: Noise plot and sim reconciliation

Part Number: OPA1656

Lets start over with the right part number in the question 

Reviewing this device for some audio work, the front page noise plot is ok, kind of a high noise corner but good for JFET, 

Here is that from the front page, a little over 30nV at 10Hz, 

The TINA reference design file includes a number of the char curves, here that is for Aol and noise (a side point, the Aol curve seems to have shift x scales for the mag and phase, hard to read - also, the stated Cload is perplexing - just trying to expand the bandwidth, handling typ parasitic, what?)

But the noise seems much higher in sim, looking 10Hz here again, looks like 60nV , corner is much higher in the model - running the sim for that model shows 61nV at 10Hz - so which is right, the front page plot or the sim model, makes a difference for those integrated noise numbers in audio,

Michael Steffes

  • Hello Michael-san,

    Thank you for pointing out.

    As I have checked the OPA1656 data sheet, I see the noise density at 100Hz is 11.8nV/rtHz in the electrical characteristics table.
    Therefore, I consider the typical noise density graph on the data sheet is correct.

    Thank you and Best regards,
    Iwata Etsuji

  • Thanks Iwata-san, kind of an odd error and easy to fix, 

    Here is the voltage noise terms in the current model, 

    The flatband number is way too low also, 2.3 vs 2.9 in the PDS

    HEre I fixed this, 

    And then comparing input voltage noise sims, gives this (the model name in the upper left seems off as well),