SBOU122B September   2013  – August 2016 INA118 , INA121 , INA122 , INA126 , INA129 , INA141 , INA155 , INA156 , INA188 , INA317 , INA818 , INA821 , INA828

 

  1.   Universal Instrumentation Amplifier Evaluation Module
    1.     Trademarks
    2. 1 Overview
      1. 1.1 Features
      2. 1.2 IA Pinout
      3. 1.3 Compatible Devices
    3. 2 PCB Layout
    4. 3 Schematic
    5. 4 EVM Components
      1. 4.1 Power
      2. 4.2 Inputs
        1. 4.2.1 Input Filtering
      3. 4.3 Output
        1. 4.3.1 Output Filtering
      4. 4.4 Reference
      5. 4.5 Prototype Area
      6. 4.6 Miscellaneous
    6. 5 Quick Start
      1. 5.1 Dual-Supply Configuration
      2. 5.2 Single-Supply Configuration
        1. 5.2.1 Direct-Reference Connection
        2. 5.2.2 Buffered-Reference Voltage Connection
    7. 6 Bill of Materials
      1. 6.1 Universal IA EVM Bill of Materials
    8. 7 Related Documentation from Texas Instruments
  2.   Revision History

5.2.2 Buffered-Reference Voltage Connection

A buffered-reference configuration is useful when the source impedance is high (for example, a voltage divider). Buffering a high-impedance source with an operational amplifier provides a low-impedance source and preserves common-mode rejection. Figure 9 shows an example of how to set up the EVM for single-supply operation with a buffered-reference voltage connection. Depending on the application, desirable single-supply buffer operational amplifiers include the OPA330, OPA376, and OPA378. The OPA277 is a good choice for high-voltage applications.

sch_singlebufref_bou122.gifFigure 9. Single-Supply Configuration, Buffered REF Connection

The following connections were made:

  1. +VS to V+ test point
  2. V+OPA to OAV+ test point
  3. GND to V– and OAV– test points
  4. VREF to OAVIN+ test point
  5. Ensure that R5 is not populated
  6. Populate R3 with a 0-Ω resistor
  7. Populate C4, C5, C11, and C12 with appropriate bypass capacitors for buffer amplifier
  8. Differential input signal to V–IN and V+IN test points
  9. Observe output at VO test point

Note that C9 and C10 are prepopulated with 0.1-µF power-supply decoupling capacitors. It is not required to remove C9 for proper single-supply operation. Refer to the device data sheet for additional power-supply decoupling information.