JAJSGR4B September   2014  – December 2018 OPA2320-Q1 , OPA320-Q1

PRODUCTION DATA.  

  1. 1 特長
  2. 2 アプリケーション
    1.     ゼロ・クロスオーバー歪み：低オフセット電圧
  3. 3 概要
  4. 4 改訂履歴
  5. 5 Pin Configuration and Functions
    1.     Pin Functions
  6. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics:
    6. 6.6 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Input and ESD Protection
      2. 7.3.2 Feedback Capacitor Improves Response
      3. 7.3.3 EMI Susceptibility And Input Filtering
      4. 7.3.4 Output Impedance
      5. 7.3.5 Capacitive Load and Stability
      6. 7.3.6 Overload Recovery Time
    4. 7.4 Device Functional Modes
      1. 7.4.1 Rail-to-Rail Input
      2. 7.4.2 Phase Reversal
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Applications
      1. 8.2.1 Transimpedance Amplifier
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
          1. 8.2.1.2.1 Optimizing The Transimpedance Circuit
        3. 8.2.1.3 Application Curves
      2. 8.2.2 High-Impedance Sensor Interface
      3. 8.2.3 Driving ADCs
      4. 8.2.4 Active Filter
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11デバイスおよびドキュメントのサポート
    1. 11.1 デバイス・サポート
      1. 11.1.1 開発サポート
    2. 11.2 関連リンク
    3. 11.3 ドキュメントの更新通知を受け取る方法
    4. 11.4 コミュニティ・リソース
    5. 11.5 商標
    6. 11.6 静電気放電に関する注意事項
    7. 11.7 Glossary
  12. 12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

7.3.5 Capacitive Load and Stability

The OPAx320-Q1 are designed to be used in applications where driving a capacitive load is required. As with all op amps, there may be specific instances where the OPAx320-Q1 can become unstable. The particular op amp circuit configuration, layout, gain, and output loading are some of the factors to consider when establishing whether an amplifier is stable in operation. An op amp in the unity-gain (1 V/V) buffer configuration and driving a capacitive load exhibits a greater tendency to become unstable than an amplifier operated at a higher noise gain. The capacitive load, in conjunction with the op amp output resistance, creates a pole within the feedback loop that degrades the phase margin. The degradation of the phase margin increases as the capacitive loading increases. When operating in the unity-gain configuration, the OPAx320-Q1 remain stable with a pure capacitive load up to approximately 1 nF.

The equivalent series resistance (ESR) of some very large capacitors (C(L) > 1 µF) is sufficient to alter the phase characteristics in the feedback loop such that the amplifier remains stable. Increasing the amplifier closed-loop gain allows the amplifier to drive increasingly larger capacitance. This increased capability is evident when observing the overshoot response of the amplifier at higher voltage gains; see Figure 32. One technique for increasing the capacitive load drive capability of the amplifier operating in unity gain is to insert a small resistor (R(S)), typically 10 Ω to 20 Ω, in series with the output, as shown in Figure 31.

This resistor significantly reduces the overshoot and ringing associated with large capacitive loads. A possible problem with this technique is that a voltage divider is created with the added series resistor and any resistor connected in parallel with the capacitive load. The voltage divider introduces a gain error at the output that reduces the output swing. The error contributed by the voltage divider may be insignificant. For instance, with a load resistance, R(L) = 10 kΩ and R(S) = 20 Ω, the gain error is only about 0.2%. However, when R(L) is decreased to 600 Ω, which the OPAx320-Q1 are able to drive, the error increases to 7.5%.

OPA320-Q1 OPA2320-Q1 ai_imprv_cl_drive_slos884.gifFigure 31. Improving Capacitive Load Drive
OPA320-Q1 OPA2320-Q1 tc_oshoot-cl_slos884.gifFigure 32. Small-Signal Overshoot versus Capacitive Load (100-mVPP Output Step)