SBOS501F January   2010  – February 2015 INA128-HT , INA129-HT

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Simplified Schematic
  5. 5 Revision History
  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: INA128-HT
    5. 7.5 Electrical Characteristics: INA128-HT
    6. 7.6 Electrical Characteristics: INA129-HT
    7. 7.7 Typical Characteristics
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
    4. 8.4 Device Functional Modes
      1. 8.4.1 Noise Performance
      2. 8.4.2 Input Common-Mode Range
  9. 9 Application and Implementation
    1. 9.1 Application Information
    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
  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
    2. 12.2 Related Links
    3. 12.3 Trademarks
    4. 12.4 Electrostatic Discharge Caution
    5. 12.5 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

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8 Detailed Description

8.1 Overview

The INA12x instrumentation amplifier is a type of differential amplifier that has been outfitted with input protection circuit and input buffer amplifiers, which eliminate the need for input impedance matching and make the amplifier particularly suitable for use in measurement and test equipment. Additional characteristics of the INA12x include a very low DC offset, low drift, low noise, very high open-loop gain, very high common-mode rejection ratio, and very high input impedances. The INA12x is used where great accuracy and stability of the circuit both short and long term are required.

8.2 Functional Block Diagram

INA128-HT INA129-HT fbd1_bos501.gif

8.3 Feature Description

The INA128-HT and INA129-HT are low power, general-purpose instrumentation amplifiers offering excellent accuracy. The versatile three-operational-amplifier design and small size make the amplifiers ideal for a wide range of applications. Current-feedback input circuitry provides wide bandwidth, even at high gain. A single external resistor sets any gain from 1 to 10,000. The INA128-HT and INA129-HT are laser trimmed for very low offset voltage (25 μV typical) and high common-mode rejection (93 dB at G ≥ 100). These devices operate with power supplies as low as ±2.25 V, and quiescent current of 2 mA, typically. The internal input protection can withstand up to ±40 V without damage.

8.4 Device Functional Modes

8.4.1 Noise Performance

The INA128-HT and INA129-HT provide very low noise in most applications. Low-frequency noise is approximately 2 μVPP measured from 0.1 Hz to 10 Hz (G ≥ 100). This provides dramatically improved noise when compared to state-of-the-art, chopper-stabilized amplifiers.

INA128-HT INA129-HT vnoise_bos501.gif
G ≥ 100
Figure 19. 0.1-Hz to 10-Hz Input-Referred Voltage Noise

8.4.2 Input Common-Mode Range

The linear input voltage ranges of the input circuitry of the INA128-HT and INA129-HT are from approximately 1.4 V below the positive supply voltage to 1.7 V above the negative supply. As a differential input voltage causes the output voltage increase, however, the linear input range will be limited by the output voltage swing of amplifiers A1 and A2. So the linear common-mode input range is related to the output voltage of the complete amplifier. This behavior also depends on supply voltage (see Figure 6 and Figure 7).

Input-overload can produce an output voltage that appears normal. For example, if an input overload condition drives both input amplifiers to their positive output swing limit, the difference voltage measured by the output amplifier will be near zero. The output of A3 will be near 0 V even though both inputs are overloaded.