SBOS830I September   2017  – October 2021 OPA189 , OPA2189 , OPA4189

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Device Comparison 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: OPA189
    5. 7.5 Thermal Information: OPA2189
    6. 7.6 Thermal Information: OPA4189
    7. 7.7 Electrical Characteristics
    8. 7.8 Typical Characteristics
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Operating Characteristics
      2. 8.3.2 Phase-Reversal Protection
      3. 8.3.3 Input Bias Current Clock Feedthrough
      4. 8.3.4 EMI Rejection
      5. 8.3.5 EMIRR +IN Test Configuration
      6. 8.3.6 Electrical Overstress
      7. 8.3.7 MUX-Friendly Inputs
      8. 8.3.8 Noise Performance
      9. 8.3.9 Basic Noise Calculations
    4. 8.4 Device Functional Modes
  9. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Applications
      1. 9.2.1 25-kHz Low-Pass Filter
        1. 9.2.1.1 Design Requirements
        2. 9.2.1.2 Detailed Design Procedure
        3. 9.2.1.3 Application Curve
      2. 9.2.2 Discrete INA + Attenuation for ADC With 3.3-V Supply
      3. 9.2.3 Bridge Amplifier
      4. 9.2.4 Low-Side Current Monitor
      5. 9.2.5 Programmable Power Supply
      6. 9.2.6 RTD Amplifier With Linearization
    3. 9.3 System Examples
      1. 9.3.1 24-Bit, Delta-Sigma, Differential Load Cell or Strain Gauge Sensor Signal Conditioning
  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
        1. 12.1.1.1 TINA-TI™ Simulation Software (Free Download)
        2. 12.1.1.2 TI Precision Designs
    2. 12.2 Documentation Support
      1. 12.2.1 Related Documentation
    3. 12.3 Receiving Notification of Documentation Updates
    4. 12.4 Support Resources
    5. 12.5 Trademarks
    6. 12.6 Electrostatic Discharge Caution
    7. 12.7 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

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

8.3.8 Noise Performance

Figure 8-5 shows the total circuit noise for varying source impedances with the operational amplifier in a unity-gain configuration (with no feedback resistor network and therefore no additional noise contributions). The OPAx189 and OPA211 are shown with total circuit noise calculated. The op amp itself contributes both a voltage noise component and a current noise component. The voltage noise is commonly modeled as a time-varying component of the offset voltage. The current noise is modeled as the time-varying component of the input bias current and reacts with the source resistance to create a voltage component of noise. Therefore, the lowest noise op amp for a given application depends on the source impedance. For low source impedance, current noise is negligible, and voltage noise generally dominates. The OPAx189 family has both low voltage noise and low current noise because of the CMOS input of the op amp. As a result, the current noise contribution of the OPAx189 series is negligible for any practical source impedance, which makes this device the better choice for applications with high source impedance.

The equation in Figure 8-5 shows the calculation of the total circuit noise, with these parameters:

  • en = voltage noise
  • in = current noise
  • RS = source impedance
  • k = Boltzmann's constant = 1.38 × 10–23 J/K
  • T = temperature in kelvins (K)

For more details on calculating noise, see the Basic Noise Calculations section.

GUID-E1315DBB-5713-4490-AAE2-06D096910D6F-low.png
NOTE: RS = 3.6 kΩ is indicated in Figure 8-5. This is the source impedance above which OPAx189 is a lower noise option than the OPA211.
Figure 8-5 Noise Performance of the OPAx189 and OPA211 in Unity-Gain Buffer Configuration