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

Abstract

Differential signals rely on the high common-mode rejection of differential amplifier circuits to reduce noise and other errors. This application note explores the relationship between resistor tolerance and common-mode rejection in difference amplifier circuits. Equations are derived to determine the common-mode rejection ratio (CMRR) of a differential amplifier circuit as a function of absolute resistance, resistor tolerance, or matched ratio tolerance. The precision ratiometric matching of the RES11A-Q1 thin-film resistor divider pair can improve the effective CMRR of a difference amplifier circuit.