SBOS062C September   2000  – January 2022 INA126 , INA2126

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: INA126
    5. 6.5 Thermal Information: INA2126
    6. 6.6 Electrical Characteristics
    7. 6.7 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
    4. 7.4 Device Functional Modes
      1. 7.4.1 Single-Supply Operation
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1 Setting the Gain
        2. 8.2.2.2 Offset Trimming
        3. 8.2.2.3 Input Bias Current Return
        4. 8.2.2.4 Input Common-Mode Range
        5. 8.2.2.5 Input Protection
        6. 8.2.2.6 Channel Crosstalk—Dual Version
      3. 8.2.3 Application Curves
  9. 9 Power Supply Recommendations
    1. 9.1 Low-Voltage Operation
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Development Support
        1. 11.1.1.1 PSpice® for TI
    2. 11.2 Receiving Notification of Documentation Updates
    3. 11.3 Support Resources
    4. 11.4 Trademarks
    5. 11.5 Electrostatic Discharge Caution
    6. 11.6 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

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

8.2.2.3 Input Bias Current Return

The input impedance of the INAx126 is extremely high at approximately 109 Ω. However, a path must be provided for the input bias current of both inputs. This input bias current is typically –10 nA (current flows out of the input pins). High input impedance means that this input bias current changes very little with varying input voltage.

Input circuitry must provide a path for this input bias current for proper operation. Figure 8-3 shows various provisions for an input bias current path. Without a bias current path, the inputs float to a potential that exceeds the common-mode range, and the input amplifiers will saturate.

If the differential source resistance is low, the bias current return path can be connected to one input (see the thermocouple example in Figure 8-3). With higher source impedance, using two equal resistors provides a balanced input with the advantages of lower input offset voltage due to bias current and better high-frequency common-mode rejection.

GUID-41E32DFD-B3CE-4FD7-9AF9-BF3F68A6C56E-low.gifFigure 8-3 Providing an Input Common-Mode Current Path