JAJSIB3D August   2017  – February 2021 THS4561


  1. 特長
  2. アプリケーション
  3. 概要
  4. Revision History
  5. Device Comparison Table
  6. Pin Configuration and Functions
  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+ – VS– = 5 V to 12 V
    6. 7.6 Typical Characteristics: (VS+) – (VS–) = 12 V
    7. 7.7 Typical Characteristics: (VS+) – (VS–) = 5 V
    8. 7.8 Typical Characteristics: (VS+) – (VS–) = 3 V
    9. 7.9 Typical Characteristics: (VS+) – (VS–) = 3-V to 12-V Supply Range
  8. Parameter Measurement Information
    1. 8.1 Example Characterization Circuits
    2. 8.2 Output Interface Circuit for DC-Coupled Differential Testing
    3. 8.3 Output Common-Mode Measurements
    4. 8.4 Differential Amplifier Noise Measurements
    5. 8.5 Balanced Split-Supply Versus Single-Supply Characterization
    6. 8.6 Simulated Characterization Curves
    7. 8.7 Terminology and Application Assumptions
  9. Detailed Description
    1. 9.1 Overview
    2. 9.2 Functional Block Diagram
    3. 9.3 Feature Description
    4. 9.4 Device Functional Modes
      1. 9.4.1 Power-Down Mode
      2. 9.4.2 Single-Ended Source to Differential Output Mode
        1. AC-Coupled Signal Path Considerations for Single-Ended Input to Differential Output Conversions
        2. DC-Coupled Input Signal Path Considerations for Single-Ended to Differential Conversions
      3. 9.4.3 Differential Input to a Differential Output Mode
        1. AC-Coupled, Differential-Input to Differential-Output Design Issues
  10. 10Application and Implementation
    1. 10.1 Application Information
      1. 10.1.1 Differential Open-Loop Gain and Output Impedance
      2. 10.1.2 Setting Resistor Values Versus Gain
      3. 10.1.3 Noise Analysis
      4. 10.1.4 Factors Influencing Harmonic Distortion
      5. 10.1.5 Input Overdrive Performance
    2. 10.2 Typical Application
      1. 10.2.1 Design Requirements
      2. 10.2.2 Detailed Design Procedure
      3. 10.2.3 Application Curves
  11. 11Power Supply Recommendations
  12. 12Layout
    1. 12.1 Layout Guidelines
      1. 12.1.1 Board Layout Recommendations
    2. 12.2 Layout Examples
  13. 13Device and Documentation Support
    1. 13.1 ドキュメントの更新通知を受け取る方法
    2. 13.2 サポート・リソース
    3. 13.3 Trademarks
    4. 13.4 静電気放電に関する注意事項
    5. 13.5 用語集
  14. 14Mechanical, Packaging, and Orderable Information



DC-Coupled Input Signal Path Considerations for Single-Ended to Differential Conversions

The output considerations remain the same as for the AC-coupled design. Again, the input can be DC-coupled when the output is ac coupled. A DC-coupled input with an AC-coupled output can have some advantages to move the input VICM down by adjusting the VOCM down if the source is ground referenced. When the source is DC-coupled into the THS4561 (see Figure 10-3), both sides of the input circuit must be DC-coupled to retain differential balance. Normally, the non-signal input side has an RG element biased to whatever the source midrange is expected to be, provided that this midscale reference gives a balanced differential swing around VOCM at the outputs. Often, RG2 is simply grounded for DC-coupled, bipolar-input applications. This configuration provides a balanced differential output if the source swings around ground. If the source swings from ground to some positive voltage, grounding RG2 gives a unipolar output differential swing from both outputs at VOCM (when the input is at ground) to one polarity of the swing. Biasing RG2 to an expected midpoint for the input signal creates a differential output swing around VOCM.

One significant consideration for a DC-coupled input is that VOCM sets up a common-mode bias current from the output back through RF and RG to the source on both sides of the feedback. Without input balancing networks, the source must sink or source this dc current. After the input signal range and biasing on the other RG element is set, check that the voltage divider from VOCM to VIN through RF and RG (and possibly RS) establishes an input VICM at the device input pins that is within the specification range. If the average source is at ground, the negative rail input stage for the THS4561 is in range for applications using a single positive supply and a positive output VOCM setting because this dc common-mode current lifts the average FDA input summing junctions above ground to a positive voltage (the average of the V+ and V– input pin voltages on the FDA). TINA-TI™ simulations of the intended circuit offer a good check for input and output pin voltage swings.