SBOSA75B July   2021  – November 2021 INA823

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 Gain-Setting Function
        1. 8.3.1.1 Gain Drift
      2. 8.3.2 Input Common-Mode Voltage Range
      3. 8.3.3 Input Protection
    4. 8.4 Device Functional Modes
  9. 9 Application and Implementation
    1. 9.1 Application Information
      1. 9.1.1 Input Bias Current Return Path
    2. 9.2 Typical Applications
      1. 9.2.1 Resistive-Bridge Pressure Sensor
        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 Supporting High Common-Mode Voltage in PLC Input Modules
        1. 9.2.2.1 Design Requirements
        2. 9.2.2.2 Detailed Design Procedure
        3. 9.2.2.3 Application Curves
  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 PSpice® for TI
    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

8.1 Overview

The INA823 is a monolithic precision instrumentation amplifier that incorporates a current-feedback input stage and a four-resistor difference-amplifier output stage. One of the features of an instrumentation amplifier (IA) is that the gain is set by placing an external resistor across the RG pins, as described in Section 8.3.1. The three-op-amp IA topology in the INA823 limits the maximum input voltage applied to the input terminal. The maximum input voltage depends on the common-mode voltage, differential voltage, gain, and the reference voltage; for more information, see Section 8.3.2. The INA823 also features protection at each input by two junction field-effect transistors (JFETs) that provide a low series resistance under normal signal conditions, and preserve excellent noise performance. When excessive voltage is applied, these transistors limit the input current, as described in Section 8.3.3.

The INA823 is developed for medical-sector applications such as infusion pumps (see Section 9.2.1), and industrial applications such as programmable logic controllers (see Section 9.2.2)

The schematic in Figure 8-1 shows how the INA823 operates. A differential input voltage is buffered by the input transistors, Q1 and Q2, and is forced across RG. This causes a signal current through RG, R1, and R2. The output difference amplifier, A3, removes the common-mode component of the input signal and refers the output signal to the REF pin. The threshold voltage of Q1 and Q2 (defined as VBE) along with the voltage drop across R1 and R2 produce output voltages on A1 and A2, respectively, that are approximately 0.8 V less than the input voltages.

Figure 8-1 Detailed Schematic