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Noise analysis of a TIA

TUKA

Dear folks!

I have made a verilogA behavioral model for a Transimpedance amplifier (TIA). It is a differential input and a differential output TIA configuration, with the inputs being I_inp and I_inn, and the outputs being Vout_p and Vout_n.

I want to do a 'noise' analysis. I have the following questions:

1) If I want to plot differential noise, then do I have to select Vout_p and Vout_n as the positive and negative output nodes respectively? 

2) In case of single ended noise, do I have to select either of Vout_p or Vout_n as the positive node and ground as the negative node?

3) Unlike the output, for the input we have the option to only select one current source or voltage node or a port or a probe. Will the resulting noise still be differential?

Thanks and regards,

Tuka

  • ShawnLogan

    Dear TUKA,

    TUKA said:
    2) In case of single ended noise, do I have to select either of Vout_p or Vout_n as the positive node and ground as the negative node?

    It depends on what specifically your single-ended common-mode voltage is for the circuit. In other words, is the single ended ouput used in your circuit with a reference voltage of ground or some common-mode generated signal? If it is not an ideal ground AC, the node chosen should reflect the impedance of your common-mode voltage node.

    TUKA said:
    3) Unlike the output, for the input we have the option to only select one current source or voltage node or a port or a probe. Will the resulting noise still be differential?

    A couple of methods proposed for creating a single-ended input source for a noise analysis when the input is differential are discussed in the Forum post at URL:

    https://community.cadence.com/cadence_technology_forums/f/custom-ic-design/41328/noise-analyses-in-cadence-for-differential-op-amp

    The second method involves using an ideal balun as means to perform differential amplifier analyses. It is described in the note at URL:

    https://support.cadence.com/apex/ArticleAttachmentPortal?id=a1Od000000050MOEAY&pageName=ArticleContent

    Shawn

  • Frank Wiedmann
    in reply to ShawnLogan
    ShawnLogan said:

    The second method involves using an ideal balun as means to perform differential amplifier analyses. It is described in the note at URL:

    https://support.cadence.com/apex/ArticleAttachmentPortal?id=a1Od000000050MOEAY&pageName=ArticleContent

    ... of which a more recent version is available at https://designers-guide.org/analysis/diff.pdf 

  • ShawnLogan
    in reply to Frank Wiedmann

    Hi Frank,

    Frank Wiedmann said:
    of which a more recent version is available at 

    Thank you for adding your note! I was not aware of the more recent version of the article!

    Shawn

  • TUKA
    in reply to Frank Wiedmann

    Dear Frank,

    Thank you for sharing the document.

    Regards,

    Tuka

  • TUKA
    in reply to ShawnLogan

    Dear Shawn,

    Thank you for getting back to me.

    I tried by connecting a souce between the two differential inputs as it was mentioned in the URL you had shared.

    I can clearly see that the noise in the differential mode is lesser than the single ended mode, which is what was expected.

    Regards,

    Tuka

  • ShawnLogan
    in reply to TUKA

    Dear TUKA,

    TUKA said:
    I can clearly see that the noise in the differential mode is lesser than the single ended mode, which is what was expected.

    Very good news! it sounds as if you are making good progress! Thank you for letting us know too!

    Shawn

  • TUKA
    in reply to ShawnLogan

    Dear Shawn,

    Thank you for the nice and encouraging words!

    Your valuable feedback and comments to all my posts have always been fruitful !!

    Thanks and regards,

    Tuka

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