SBOS051F October   1995  – May 2022 INA128 , INA129

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
    5. 7.5 Electrical Characteristics
    6. 7.6 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 Noise Performance
    4. 8.4 Device Functional Modes
  9. 9 Application and Implementation
    1. 9.1 Application Information
      1. 9.1.1 Input Common-Mode Range
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
        1. 9.2.2.1 Setting the Gain
        2. 9.2.2.2 Dynamic Performance
        3. 9.2.2.3 Offset Trimming
        4. 9.2.2.4 Input Bias Current Return Path
      3. 9.2.3 Application Curves
    3. 9.3 System Examples
  10. 10Power Supply Recommendations
    1. 10.1 Low-Voltage Operation
  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 PSpice® for TI
        2. 12.1.1.2 TINA-TI™ Simulation Software (Free Download)
    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

9.2.2.1 Setting the Gain

The gain (G) is set by connecting a single external resistor, RG, between pins 1 and 8:

Equation 1. INA128: G = 1 + 50 kΩ / RG
Equation 2. INA129: G = 1 + 49.4 kΩ / RG

Commonly used gains and resistor values are shown in Figure 9-1.

The 50-kΩ term in Equation 1 and the 49.4-kΩ term in Equation 2 come from the sum of the two internal feedback resistors of A1 and A2. These on-chip metal film resistors are laser trimmed to accurate, absolute values. The accuracy and temperature coefficient of these internal resistors are included in the gain accuracy and drift specifications in the Electrical Characteristics table.

The stability and temperature drift of the external gain setting resistor, RG, also affects gain. The contribution of RG to gain accuracy and drift can be directly inferred from Equation 1 and Equation 2. Low resistor values required for high gain can make wiring resistance important. Sockets add to the wiring resistance, which contributes additional gain error (possibly an unstable gain error) in gains of approximately 100 or greater.