SBOS492G June   2009  – August 2026 OPA2354A-Q1 , OPA354A-Q1 , OPA4354-Q1

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Pin Configuration and Functions
  6. 5 Specifications
    1. 5.1 Absolute Maximum Ratings
    2. 5.2 ESD Ratings
    3. 5.3 Recommended Operating Conditions
    4. 5.4 Thermal Information
    5. 5.5 Electrical Characteristics
    6. 5.6 Typical Characteristics
  7. 6 Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagram
    3. 6.3 Feature Description
      1. 6.3.1 Operating Voltage
      2. 6.3.2 Rail-to-Rail Input
      3. 6.3.3 Rail-to-Rail Output
      4. 6.3.4 Output Drive
      5. 6.3.5 Video
      6. 6.3.6 Driving Analog-to-Digital Converters
      7. 6.3.7 Capacitive Load and Stability
      8. 6.3.8 Wideband Transimpedance Amplifier
    4. 6.4 Device Functional Modes
  8. 7 Application and Implementation
    1. 7.1 Application Information
    2. 7.2 Typical Applications
      1. 7.2.1 Transimpedance Amplifier
        1. 7.2.1.1 Design Requirements
        2. 7.2.1.2 Detailed Design Procedure
          1. 7.2.1.2.1 Optimizing The Transimpedance Circuit
        3. 7.2.1.3 Application Curve
      2. 7.2.2 High-Impedance Sensor Interface
      3. 7.2.3 Driving ADCs
      4. 7.2.4 Active Filter
    3. 7.3 Power Supply Recommendations
      1. 7.3.1 Power Dissipation
    4. 7.4 Layout
      1. 7.4.1 Layout Guidelines
      2. 7.4.2 Layout Example
  9. 8 Device and Documentation Support
    1. 8.1 Documentation Support
      1. 8.1.1 Related Documentation
    2. 8.2 Receiving Notification of Documentation Updates
    3. 8.3 Support Resources
    4. 8.4 Trademarks
    5. 8.5 Electrostatic Discharge Caution
    6. 8.6 Glossary
  10. 9 Revision History
  11. 10Mechanical, Packaging, and Orderable Information

6.3.7 Capacitive Load and Stability

The OPAx354-Q1 family op amps can drive a wide range of capacitive loads. However, all op-amps under certain conditions can become unstable. Op amp configuration, gain, and load value are a few of the factors to consider when determining stability. An op amp in unity-gain configuration is most susceptible to the effects of capacitive loading. The capacitive load reacts with the output resistance of the op amp, along with any additional load resistance, to create a pole in the small-signal response that degrades the phase margin. For details, see Figure 5-15 (Frequency Response vs Capacitive Load.)

The OPAx354-Q1 topology enhances the ability of the device to drive capacitive loads. In unity gain, these op-amps perform well with large capacitive loads. For details see Figure 5-14, Recommended RS vs Capacitive Load, and Figure 5-15, Frequency Response vs Capacitive Load.

Insert a 10Ω to 20Ω resistor in series with the output to improve capacitive laod drive in the unity-gain configuration, as shown in Figure 6-6. This configuration significantly reduces ringing with large capacitive loads; see Figure 5-15 (Frequency Response vs Capacitive Load.) However, if a resistive load is in parallel with the capacitive load, RS creates a voltage divider. This configuration introduces a DC error at the output and slightly reduces output swing. This error may be insignificant. For example, if RL = 10kΩ and RS = 20Ω, the error at the output is approximately 0.2%.

OPA354A-Q1 OPA2354A-Q1 OPA4354-Q1 Series Resistor in Unity-Gain Configuration Improves Capacitive Load DriveFigure 6-6 Series Resistor in Unity-Gain Configuration Improves Capacitive Load Drive