SBOA570 may   2023 LMC6061 , LMC6081 , OPA192 , OPA2277 , OPA2350 , OPA277 , OPA320 , OPA328 , OPA350 , OPA391 , OPA392 , OPA4277 , OPA4350

 

  1.   Abstract
  2.   Trademarks
  3. 1 Introduction
  4. 2  Current Noise Versus Frequency
  5. 3 How the SPICE Model Sets Current Noise
  6. 4 Impact Current Noise has on a Non-inverting Amp With Large Source Impedance
  7. 5 Impact of Current Noise has on the Transimpedance Configuration
  8. 6 Current Noise Correlation
  9. 7 Measuring Low Current Noise Levels
  10. 8 Low Current Noise and Bias Current Considerations
  11. 9 Summary
  12. 10References

9 Summary

Very low current noises do not impact overall noise performance unless the source impedance is very large. In the case of a 1fA/√Hz current noise, the source resistance needs to be greater than 16.5 GΩ for current noise to make a significant contribution to overall noise. For CMOS and JFET devices, it is common for current noise to increase at higher frequencies. This increase in current noise is called f-squared noise. Circuits where the source impedance is high limit, the bandwidth below the frequency where current noise begins to increase. This bandwidth limitation tends to counterbalance the impact of the f-squared noise so that the total RMS noise is not impacted significantly by the f-squared noise.