SLOS713J January   2011  – March 2021 OPA2835 , OPA835

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Device Comparision Table
  6. 6 Pin Configuration and Functions
  7. 7 Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information: OPA835
    5. 7.5 Thermal Information: OPA2835
    6. 7.6 Electrical Characteristics: VS = 2.7 V
    7. 7.7 Electrical Characteristics: VS = 5 V
    8. 7.8 Typical Characteristics: VS = 2.7 V
    9. 7.9 Typical Characteristics: VS = 5 V
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Input Common-Mode Voltage Range
      2. 8.3.2 Output Voltage Range
      3. 8.3.3 Power-Down Operation
      4. 8.3.4 Low-Power Applications and the Effects of Resistor Values on Bandwidth
      5. 8.3.5 Driving Capacitive Loads
    4. 8.4 Device Functional Modes
      1. 8.4.1 Split-Supply Operation (±1.25 V to ±2.75 V)
      2. 8.4.2 Single-Supply Operation (2.5 V to 5.5 V)
  9. 9 Application and Implementation
    1. 9.1 Application Information
      1. 9.1.1  Noninverting Amplifier
      2. 9.1.2  Inverting Amplifier
      3. 9.1.3  Instrumentation Amplifier
      4. 9.1.4  Attenuators
      5. 9.1.5  Single-Ended to Differential Amplifier
      6. 9.1.6  Differential to Single-Ended Amplifier
      7. 9.1.7  Differential-to-Differential Amplifier
      8. 9.1.8  Gain Setting With OPA835 RUN Integrated Resistors
      9. 9.1.9  Pulse Application With Single-Supply
      10. 9.1.10 ADC Driver Performance
    2. 9.2 Typical Application
      1. 9.2.1 Audio Frequency Performance
        1. 9.2.1.1 Design Requirements
        2. 9.2.1.2 Detailed Design Procedure
        3. 9.2.1.3 Application Curves
      2. 9.2.2 Active Filters
        1. 9.2.2.1 Application Curve
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Device Support
      1. 12.1.1 Development Support
    2. 12.2 Documentation Support
      1. 12.2.1 Related Documentation
    3. 12.3 Related Links
    4. 12.4 Receiving Notification of Documentation Updates
    5. 12.5 Support Resources
    6. 12.6 Trademarks
    7. 12.7 Electrostatic Discharge Caution
    8. 12.8 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

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

8.3.4 Low-Power Applications and the Effects of Resistor Values on Bandwidth

The OPA835 and OPA2835 devices are designed for the nominal value of RF to be 2 kΩ in gains other than +1. This gives excellent distortion performance, maximum bandwidth, best flatness, and best pulse response. It also loads the amplifier. For example; in gain of 2 with RF = RG = 2 kΩ, RG to ground, and VOUT = 4 V, 1 mA of current will flow through the feedback path to ground. In gain of +1, RG is open and no current will flow to ground. In low-power applications, it is desirable to reduce the current in the feedback path by increasing the gain-setting resistors values. Using larger value gain resistors has two primary side effects (other than lower power) due to their interaction with parasitic circuit capacitance.

  • Lowers the bandwidth
  • Lowers the phase margin
    • This causes peaking in the frequency response
    • This causes overshoot and ringing in the pulse response

Figure 8-3 shows the small-signal frequency response on OPA835EVM for noninverting gain of 2 with RF and RG equal to 2 kΩ, 10 kΩ, and 100 kΩ. The test was done with RL = 2 kΩ. Due to loading effects of RL, lower RL values may reduce the peaking, but higher values will not have a significant effect.

GUID-CEF630E9-33B1-4C29-BF8E-8CB2AEEFD804-low.gifFigure 8-3 Frequency Response With Various Gain-Setting Resistor Values

As expected, larger value gain resistors cause lower bandwidth and peaking in the response (peaking in frequency response is synonymous with overshoot and ringing in pulse response). Adding 1-pF capacitors in parallel with RF helps compensate the phase margin and restores flat frequency response. Figure 8-4 shows the test circuit.

GUID-692EEEBA-5840-47AA-A36B-3F80D9FE332F-low.gif Figure 8-4 G = 2 Test Circuit for Various Gain-Setting Resistor Values