ZHCSNI6 march   2023 OPA928

ADVANCE INFORMATION  

  1. 1 特性
  2. 2 应用
  3. 3 说明
  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.     Thermal Information
    5. 6.4 Electrical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Guard Buffer
      2. 7.3.2 Thermal Protection
      3. 7.3.3 Capacitive Load and Stability
      4. 7.3.4 EMI Rejection
      5. 7.3.5 Common-Mode Voltage Range
    4. 7.4 Device Functional Modes
  8. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 Contamination Considerations
      2. 8.1.2 Guarding Considerations
      3. 8.1.3 Humidity Considerations
      4. 8.1.4 Dielectric Relaxation
    2. 8.2 Typical Applications
      1. 8.2.1 High-Impedance (Hi-Z) Amplifier
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
        3. 8.2.1.3 Application Curve
      2. 8.2.2 Transimpedance Amplifier
        1. 8.2.2.1 Design Requirements
        2. 8.2.2.2 Detailed Design Procedure
    3. 8.3 Power-Supply Recommendations
    4. 8.4 Layout
      1. 8.4.1 Layout Guidelines
      2. 8.4.2 Layout Examples
  9. 9 Device and Documentation Support
    1. 9.1 Device Support
      1. 9.1.1 Development Support
        1. 9.1.1.1 PSpice® for TI
        2. 9.1.1.2 TINA-TI™ 仿真软件（免费下载）
        3. 9.1.1.3 TI 参考设计
    2. 9.2 Documentation Support
      1. 9.2.1 Related Documentation
    3. 9.3 接收文档更新通知
    4. 9.4 支持资源
    5. 9.5 Trademarks
    6. 9.6 静电放电警告
    7. 9.7 术语表
  10. 10Mechanical, Packaging, and Orderable Information

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8.2.1 High-Impedance (Hi-Z) Amplifier

The OPA928 behaves very close to an ideal op amp in regards to the input current. The near-zero input bias current performance enables applications with extremely high impedance signal sources. For example, pH probes can have an output impedance of up to 10 GΩ. Most op amps are inadequate to use with this kind of sensor impedance. For example, a CMOS op amp with 1 pA of input bias current loads the sensor and causes a large, and unacceptable, 10-mV error at the input. In Figure 8-3, the OPA928 is used to gain up the small signal from the pH probe sensor. The large input impedance and ultra-low bias current into the positive input pin of the OPA928 does not load the sensor and minimizes the input bias current error.

GUID-20230118-SS0I-JHTK-Q5Z7-BH4CCBCX9J75-low.svg Figure 8-3 High Impedance pH Probe Amplifier Circuit