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1.3 Troubleshooting Tips: Op Amps - Common Mode Rejection Ratio

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Date: May 30, 2019

Understanding how to verify datasheet specifications such as common mode rejection ratio (change in offset versus change in common mode) is critical to the application troubleshooting and debugging process. In this training the false summing junction circuit is utilized to demonstrate how to determine the CMRR of a linear amplifier. At the system level an offset anomaly versus input common mode voltage may result in the following signatures:

  • Increased or decreased output voltage compared to the nominal

  • Anomalous reading observed by ADC

  • Unexpected sensor reading

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