SLOA332A July   2023  – September 2024 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. 1 Slew Rate Definition
    1. 1.1 Virtual Ground and Slew Rate
  5. 2 Bipolar Op Amp Slew Rate Example
  6. 3 CMOS 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. 4 Four Methods to Determine Boost or No Boost Using the Data Sheet
    1. 4.1 Method 1: Compare Slew Rate Versus Gain Bandwidth
    2. 4.2 Method 2: Compare Quiescent Current Versus Similar SR Devices
    3. 4.3 Method 3: Evaluate Large Signal Response
    4. 4.4 Method 4: Evaluate Small Signal Response
  8. 5 Slew Rate Dependencies on Circuit Signal Levels and Op Amp Gain Set by Feedback Network
  9. 6 How Much Output Slew Rate is Needed to Support a Sine Wave or Other Non-step Inputs
  10. 7 Stability Also Plays a Role in Observed Slew Rate
  11. 8 Summary
  12. 9 References
  13. 10Revision History

3 CMOS Op Amp Slew Rate Example

CMOS op amps replace NPN and PNP transistors with NMOS and PMOS transistors. The bias current split is based on voltage difference squared plus a linear factor. Therefore, expect some variation between different CMOS op amps. TLV9001 data is charted in Figure 3-1 up to 100mV. The curve in Figure 3-1 looks similar to the bipolar example for VID. Most other CMOS amplifiers show similar behavior. Figure 3-1 is referenced throughout this application note, see Section 4 and Section 5.

TS321, TL074, TLV9001, OPA4991, OPA2991, OPA991, LMV831, OPA345, LMV821-N, OPA377-Q1, OPA376-Q1, OPA377, OPA376, TLV376, TLV9002 CMOS SR/SR[max] Versus VID Figure 3-1 CMOS SR/SR[max] Versus VID

For the TLV9001, 100% of the maximum natural slew rate occurs with VID >> 100mV. However, the internal bias current (B) and CC capacitor give 0.5V/µs slew rate, not the 2V/µs stated in the data sheet. The TLV9001 employs a slew boost circuit to raise the slew rate to 2V/µs. Figure 3-1 is the natural slew rate based solely on bias current and compensation capacitance with the inactive boost circuit.