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LMH3401: Common mode voltage

Samaneh Afshar
Intellectual 330 points
Part Number: LMH3401

Hello all,

In application document for LMH3401 it is mentioned that the" device performance is optimal when the output common-mode voltage (VOCM ) is within ±0.5 V of

mid-supply and performance degrades outside the range when the output swing approaches clipping". Also it is mentioned that "the VOCM  range extends from 1.1

V below the mid-supply voltage to 1.1 V above the mid-supply voltage when using a 5-V supply levels.

I appreciate if you elaborate more about the two different ranges that are defined here.

Thank you,

Samaneh

  • 0
    TI__Expert 3126 points

    Hello Afshar .

    So as you can see both the points hold true .

    The output common mode range defines the range for which the output differential gain shift from its original gain by 1db.

    this range is basically defined by the spec table shown below .

    The other point says that the output is optimal when Common mode is +/- 0.5V from the mid supply .

    This spec or sentence is mentioned as it dictates the quality of the output being reproduced .

    The distortion performance vs Common mode graph will help us clearly see that as the common mode goes away from the midsupply the distortion will increase dramatically hence datasheet requests to keep Common mode close to mid-supply .

  • 0
    Guru 140200 points

    Hi Samaneh,

    when you carefully look at the distortion plots of datasheet you will see that the best performance can be achieved with a maximum supply voltage (5V), Vcm = middsupply and the common mode input voltage and common mode output voltage also at midsupply.

    Kai

  • 0 in reply to Shreenidhi Patil
    Intellectual 330 points

    Hi Shreenidhi,

    Thank you for the clarification. 

    Regards,

    Samaneh

  • 0 in reply to kai klaas69
    Intellectual 330 points

    Hi Kai,

    Thanks a lot for the clarification.

    Regards,

    Samaneh