SLOA332 july   2023 LMV821-N , LMV831 , OPA2991 , OPA345 , OPA376 , OPA376-Q1 , OPA377 , OPA377-Q1 , OPA4991 , OPA991 , TL074 , TLV376 , TLV9001 , TLV9002 , TS321

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Slew Rate Definition
    1. 1.1 Virtual Ground and Slew Rate
  5. 2Bipolar Op Amp Slew Rate Example
  6. 3CMOS Op Amp Slew Rate Example
    1. 3.1 Slew Boost Example 1
    2. 3.2 Slew Boost Example 2
    3. 3.3 Slew Boost Summary
  7. 4Four Methods to Determine Boost or No Boost Using the Data Sheet
  8. 5Slew Rate Dependencies on Circuit Signal Levels and Op Amp Gain Set by Feedback Network
  9. 6How Much Output Slew Rate is Needed to Support a Sine Wave or Other Non-step Inputs
  10. 7Stability Also Plays a Role in Observed Slew Rate
  11. 8Summary
  12. 9References

Abstract

This application note discusses the discrepancy between the slew rate in applications and the slew rate specifications in op amp data sheets. The virtual ground (or virtual zero) concept simplifies op amp design by assuming the voltage difference between the inputs, VID, is zero. VID must increase to generate slew rate. Just over 100 mV are needed to reach the maximum natural slew rate that is listed in many data sheets. Some op amps have a data sheet slew rate greater than natural slew rate by incorporating a slew boost circuit. The VID needed to reach boosted slew rate may be several hundreds of millivolts. Most data sheets do not state the presence of slew boost; however, there are methods to determine the presence of slew boost by examining the data sheet figures with waveforms.