SBOA582 November   2023 OPA2387 , OPA387 , OPA4387 , RES11A , RES11A-Q1

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction to Differential Signaling
  5. 2Common-Mode Rejection Ratio in Difference Amplifier Circuits
  6. 3Improving CMRR with Precision Matched Resistor Divider Pairs, RES11A-Q1
  7. 4Derive Differential and Common-Mode Gain, Difference Amplifier
  8. 5Derive CMRR for Discrete Resistor Tolerance
  9. 6Derive CMRR for Matched Ratio Tolerance
  10. 7Summary
  11. 8References

7 Summary

The common-mode rejection ratio (CMRR) of a difference amplifier is dominated by the matched ratio tolerance of the resistor network. The matched ratio tolerance of four discrete resistors can be up to four times the magnitude of each resistor's absolute tolerance. The RES11A-Q1 data sheet specifies matched ratio tolerance, tm, which can be used to directly calculate the minimum and typical CMRR when configured in a differential amplifier circuit. Equations were derived to determine the CMRR of a difference amplifier as a function of absolute resistance, discrete resistor tolerance, and matched ratio tolerance. The RES11A-Q1 features precision ratiometric matching to improve the effective CMRR of differential amplifier circuits.