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YLi.12
Visitor II
February 17, 2023
Solved

STM32L476 OPAMP CMRR Measurement methods

  • February 17, 2023
  • 2 replies
  • 1592 views

Currently doing academic research.

There are few descriptions in the specification, how to measure CMRR?0693W00000aH3ckQAC.png

    This topic has been closed for replies.
    Best answer by FBL

    Hello @Community member​ 

    CMRR is a basic electronic measurement and calculated as the ratio of the differential gain to the common-mode gain. You may refer to AN4586 as an example of an implementation to highlight the importance of having very accurate resistors.

    Hope this could be an enhancement to guide you on how to calculate CMRR.

    2 replies

    F
    FBLAnswer
    Technical Moderator
    February 22, 2023

    Hello @Community member​ 

    CMRR is a basic electronic measurement and calculated as the ratio of the differential gain to the common-mode gain. You may refer to AN4586 as an example of an implementation to highlight the importance of having very accurate resistors.

    Hope this could be an enhancement to guide you on how to calculate CMRR.

    L
    LCE
    Graduate II
    February 22, 2023

    The most simple way:

    • connect the signal output of a single-ended source to both differential inputs
    • connect the ground of the source to the same ground that the amp-under-test refers to
    • measure amp output, compare to input

    Edit: careful, do not connect any signal generator directly to the controller!

    In case of testing a "VCC"-supplied device, it's safest to use the output a single-supply-RRIO-opamp which is also supplied with VCC as a signal source

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