ZHCSGM4C August   2017  – October 2023 OPA838

PRODUCTION DATA  

  1.   1
  2. 1 特性
  3. 2 应用
  4. 3 说明
  5. 4 Revision History
  6. 5 Device Comparison Table
  7. 6 Pin Configuration and Functions
  8. 7 Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics: VS = 5 V
    6. 7.6 Electrical Characteristics: VS = 3 V
    7. 7.7 Typical Characteristics: VS = 5 V
    8. 7.8 Typical Characteristics: VS = 3 V
    9. 7.9 Typical Characteristics: Over Supply Range
  9. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Input Common-Mode Voltage Range
      2. 8.3.2 Output Voltage Range
      3. 8.3.3 Power-Down Operation
      4. 8.3.4 Trade-Offs in Selecting The Feedback Resistor Value
      5. 8.3.5 Driving Capacitive Loads
    4. 8.4 Device Functional Modes
      1. 8.4.1 Split-Supply Operation (±1.35 V to ±2.7 V)
      2. 8.4.2 Single-Supply Operation (2.7 V to 5.4 V)
      3. 8.4.3 Power Shutdown Operation
  10. 9 Application and Implementation
    1. 9.1 Application Information
      1. 9.1.1 Noninverting Amplifier
      2. 9.1.2 Inverting Amplifier
      3. 9.1.3 Output DC Error Calculations
      4. 9.1.4 Output Noise Calculations
    2. 9.2 Typical Applications
      1. 9.2.1 High-Gain Differential I/O Designs
        1. 9.2.1.1 Design Requirements
        2. 9.2.1.2 Detailed Design Procedure
        3. 9.2.1.3 Application Curves
      2. 9.2.2 Transimpedance Amplifier
        1. 9.2.2.1 Design Requirements
        2. 9.2.2.2 Detailed Design Procedure
        3. 9.2.2.3 Application Curve
    3. 9.3 Power Supply Recommendations
    4. 9.4 Layout
      1. 9.4.1 Layout Guidelines
      2. 9.4.2 Layout Example
  11. 10Device and Documentation Support
    1. 10.1 Device Support
      1. 10.1.1 TINA-TI™ Simulation Model Features
    2. 10.2 Documentation Support
      1. 10.2.1 Related Documentation
    3. 10.3 接收文档更新通知
    4. 10.4 支持资源
    5. 10.5 Trademarks
    6. 10.6 静电放电警告
    7. 10.7 术语表
  12.   Mechanical, Packaging, and Orderable Information

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9.1.4 Output Noise Calculations

The decompensated voltage feedback of the OPA838 op amp offers among the lowest input voltage and current noise terms for any device with a supply current less than 1 mA. Figure 9-3 shows the op amp noise analysis model that includes all noise terms. In this model, all the noise terms are shown as noise voltage or current density terms in nV/√Hz or pA/√Hz.

GUID-F7899AD9-BDB5-4640-AAFA-8B098761255F-low.gifFigure 9-3 Op-Amp Noise-Analysis Model

The total output spot noise voltage is computed as the square root of the squared contributing terms to the output noise voltage. This computation is adding all the contributing noise powers at the output by superposition, then taking the square root to return to a spot noise voltage. Equation 3 shows the general form for this output noise voltage using the terms presented in Figure 9-3.

Equation 3. GUID-F27F3F8E-56C3-4BF0-9958-AB1B8B581906-low.gif

Dividing this expression by the noise gain (NG = 1 + RF / RG) gives the equivalent input-referred spot noise voltage at the noninverting input, as shown in Equation 4.

Equation 4. GUID-0850B0BA-70AC-4955-81D6-503711B38F38-low.gif

Using the resistor values shown in Table 9-1 with RS = 0 Ω results in a constant input-referred voltage noise of 2.86 nV/√Hz. Reducing the resistor values brings this number closer to the intrinsic 1.9 nV/√Hz of the OPA838. Adding RS for bias current cancellation in noninverting mode adds the noise from RS to the total output noise; see Equation 3. In inverting mode, bypass the RS bias-current cancellation resistor with a capacitor for the best noise performance.