JAJSFT1E August   2011  – April 2018 OPA170 , OPA2170 , OPA4170

PRODUCTION DATA.  

  1. 1 特長
  2. 2 アプリケーション
    1.     36Vオペアンプの最小パッケージ
  3. 3 概要
  4. 4 改訂履歴
  5. 5 Device Comparison Table
  6. 6 Pin Configuration and Functions
    1.     Pin Functions: OPA170
    2.     Pin Functions: OPA2170
    3.     Pin Functions: OPA4170
  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: OPA170
    5. 7.5 Thermal Information: OPA2170
    6. 7.6 Thermal Information: OPA4170
    7. 7.7 Electrical Characteristics
    8. 7.8 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 Operating Characteristics
      2. 8.3.2 Phase-Reversal Protection
      3. 8.3.3 Electrical Overstress
      4. 8.3.4 Capacitive Load and Stability
    4. 8.4 Device Functional Modes
      1. 8.4.1 Common-Mode Voltage Range
      2. 8.4.2 Overload Recovery
  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 Custom Design With WEBENCH® Tools
        2. 9.2.2.2 Unity-Gain Buffer
      3. 9.2.3 Application Curve
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12デバイスおよびドキュメントのサポート
    1. 12.1 デバイス・サポート
      1. 12.1.1 デベロッパー・ネットワークの製品に関する免責事項
      2. 12.1.2 開発サポート
        1. 12.1.2.1 TINA-TI™ (無料のダウンロード・ソフトウェア)
        2. 12.1.2.2 DIPアダプタ評価モジュール
        3. 12.1.2.3 ユニバーサル・オペアンプ評価モジュール
        4. 12.1.2.4 TI Precision Designs
        5. 12.1.2.5 WEBENCH Filter Designer
        6. 12.1.2.6 WEBENCH®ツールによるカスタム設計
    2. 12.2 ドキュメントのサポート
      1. 12.2.1 関連資料
    3. 12.3 関連リンク
    4. 12.4 ドキュメントの更新通知を受け取る方法
    5. 12.5 コミュニティ・リソース
    6. 12.6 商標
    7. 12.7 静電気放電に関する注意事項
    8. 12.8 Glossary
  13. 13メカニカル、パッケージ、および注文情報

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

9.2.2.2 Unity-Gain Buffer

Figure 41 shows a unity-gain buffer driving a capacitive load. Equation 1 shows the transfer function for the circuit in Figure 41. Not shown in Figure 41 is the open-loop output resistance of the operational amplifier, Ro.

Equation 1. OPA170 OPA2170 OPA4170 ai_refdes_eqn_bos618.gif

The transfer function in Equation 1 has a pole and a zero. The frequency of the pole (fp) is determined by (Ro + RISO) and CLOAD. Components RISO and CLOAD determine the frequency of the zero (fz). A stable system is obtained by selecting RISO such that the rate of closure (ROC) between the open-loop gain (AOL) and 1/β is 20 dB/decade. Figure 42 depicts the concept. The 1/β curve for a unity-gain buffer is 0 dB.

OPA170 OPA2170 OPA4170 ai_refdes_bodeplot_bos618.gifFigure 42. Unity-Gain Amplifier With RISO Compensation

ROC stability analysis is typically simulated. The validity of the analysis depends on multiple factors, especially the accurate modeling of Ro. In addition to simulating the ROC, a robust stability analysis includes a measurement of overshoot percentage and ac gain peaking of the circuit using a function generator, oscilloscope, and gain and phase analyzer. Phase margin is then calculated from these measurements. Table 3 shows the overshoot percentage and ac gain peaking that correspond to phase margins of 45° and 60°. For more details on this design and other alternative devices that can be used in place of the OPA170, see the Precision Design, Capacitive Load Drive Solution Using an Isolation Resistor.

Table 3. Phase Margin versus Overshoot and AC Gain Peaking

PHASE MARGIN OVERSHOOT AC GAIN PEAKING
45° 23.3% 2.35 dB
60° 8.8% 0.28 dB