SBOS512E March   2010  – November 2020 OPA2365-Q1 , OPA365-Q1

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
  6. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics
    6. 6.6 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Operating Characteristics
      2. 7.3.2 Basic Amplifier Configurations
      3. 7.3.3 Input and ESD Protection
      4. 7.3.4 Rail-to-Rail Input
    4. 7.4 Device Functional Modes
  8. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 Capacitive Loads
      2. 8.1.2 Achieving an Output Level of Zero Volts (0 V)
      3. 8.1.3 Active Filtering
      4. 8.1.4 Driving an ADS7822-Q1 Analog-to-Digital Converter
      5. 8.1.5 Driving ADS1115-Q1 Analog-to-Digital Converter
    2. 8.2 Typical Application
      1. 8.2.1 Fast Settling Peak Detector
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
        3. 8.2.1.3 Application Curves
      2. 8.2.2 Bandpass Filter 1.5 kHz to 160 kHz and 40-db Flat Gain
        1. 8.2.2.1 Design Requirements
        2. 8.2.2.2 Detailed Design Procedure
        3. 8.2.2.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Documentation Support
      1. 11.1.1 Related Documentation
    2. 11.2 Support Resources
    3. 11.3 Trademarks
    4. 11.4 Electrostatic Discharge Caution
    5. 11.5 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

8.1.1 Capacitive Loads

The OPA365-Q1 device may be used in applications where driving a capacitive load is required. As with all operational amplifiers, there may be specific instances where the OPA365-Q1 device can become unstable, leading to oscillation. The particular operational amplifier circuit configuration, layout, gain and output loading are some of the factors to consider when establishing whether an amplifier will be stable in operation. An operational amplifier in the unity-gain (1 V/V) buffer configuration and driving a capacitive load exhibits a greater tendency to be unstable than an amplifier operated at a higher noise gain. The capacitive load, in conjunction with the operational amplifier output resistance, creates a pole within the feedback loop that degrades the phase margin. The degradation of the phase margin increases as the capacitive loading increases.

When operating in the unity-gain configuration, the OPA365-Q1 device remains stable with a pure capacitive load up to approximately 1 nF. The equivalent series resistance (ESR) of some very large capacitors (CL > 1 µF) is sufficient to alter the phase characteristics in the feedback loop such that the amplifier remains stable. Increasing the amplifier closed-loop gain allows the amplifier to drive increasingly larger capacitance. This increased capability is evident when observing the overshoot response of the amplifier at higher voltage gains. See Figure 6-15.

One technique for increasing the capacitive load drive capability of the amplifier operating in unity gain is to insert a small resistor, typically 10 Ω to 20 Ω, in series with the output; see Figure 8-1. This resistor significantly reduces the overshoot and ringing associated with large capacitive loads. A possible problem with this technique is that a voltage divider is created with the added series resistor and any resistor connected in parallel with the capacitive load. The voltage divider introduces a gain error at the output that reduces the output swing. The error contributed by the voltage divider may be insignificant. For instance, with a load resistance, RL = 10 kΩ, and RS = 20 Ω, the gain error is only about 0.2%. However, when RL is decreased to 600 Ω, which the OPA365-Q1 device is able to drive, the error increases to 7.5%.

GUID-3FE45A81-6402-4C39-8D04-B0C7D52F83FE-low.gifFigure 8-1 Improving Capacitive Load Drive