JAJSLE9 march   2023 OPA928

ADVANCE INFORMATION  

  1. 1 特長
  2. 2 アプリケーション
  3. 3 説明
  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™シミュレーション・ソフトウェア (無償ダウンロード)
        3. 9.1.1.3 TI のリファレンス・デザイン
    2. 9.2 Documentation Support
      1. 9.2.1 Related Documentation
    3. 9.3 ドキュメントの更新通知を受け取る方法
    4. 9.4 サポート・リソース
    5. 9.5 Trademarks
    6. 9.6 静電気放電に関する注意事項
    7. 9.7 用語集
  10. 10Mechanical, Packaging, and Orderable Information

パッケージ・オプション

メカニカル・データ（パッケージ｜ピン）
サーマルパッド・メカニカル・データ
発注情報

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