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. Slew Rate Definition
    1. 1.1 Virtual Ground and Slew Rate
  5. Bipolar Op Amp Slew Rate Example
  6. 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. 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. Slew Rate Dependencies on Circuit Signal Levels and Op Amp Gain Set by Feedback Network
  9. How Much Output Slew Rate is Needed to Support a Sine Wave or Other Non-step Inputs
  10. Stability Also Plays a Role in Observed Slew Rate
  11. Summary
  12. References
  13. 10Revision History

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.