SBOA550 October   2022 OPA1671 , OPA2990 , SN74HCS04 , SN74HCS164 , SN74HCS30 , SN74LVC1G00 , SN74LVC1G123 , TLC04 , TLC14 , TS5A9411


  1.   Abstract
  2.   Trademarks
  3. Introduction
  4. The Davies Generator
  5. Optimizing Standard Resistance Values for THD Performance
  6. Simulation Examples
  7. Compensating for Shift Register Output Resistance
  8. Voltage-Mode Thevenin Equivalent
  9. Harmonic Filtering
  10. Tracking Harmonic Filter
  11. Multiphase Output
  12. 10Conclusion
  13. 11Acknowledgment
  14. 12References
  15.   A Analytical Solution for Resistance Network Values
  16.   B Forbidden States of the Johnson Counter


Good quality sinusoidal waveforms can be deceptively difficult to generate. Traditional continuous-time circuits such as the Wien bridge oscillator are simple in principle, but require much additional non-linear circuitry for good performance. It is also becoming difficult to source the components (such as incandescent light bulbs and JFETs) to build the old continuous-time designs. Discrete time solutions usually require expensive precision digital-to-analog converters (DAC) and significant digital logic and firmware that can be too burdensome for many applications. This application note discusses how to use simple Medium Scale Integrated (MSI) logic along with resistors and amplifiers to generate waveforms having well-defined frequency and amplitude, while also providing relatively good harmonic distortion performance.