JAJU648A November   2018  – April 2022 TLV3601 , TLV3601-Q1 , TLV3603 , TLV3603-Q1

 

  1.   概要
  2.   Resources
  3.   特長
  4.   アプリケーション
  5.   5
  6. 1System Description
    1. 1.1 Key System Specifications
  7. 2System Overview
    1. 2.1 Block Diagram
    2. 2.2 Design Considerations
      1. 2.2.1 Amplifier and Comparator
      2. 2.2.2 Digital Processing and Control
      3. 2.2.3 Optical Components
        1. 2.2.3.1 Laser Driver and Laser Diode
        2. 2.2.3.2 Photodiode
      4. 2.2.4 Power Supply
    3. 2.3 Highlighted Products
      1. 2.3.1 OPA858 Operational Amplifier
      2. 2.3.2 TLV3501 and TLV3601/3 High-Speed Comparators
      3. 2.3.3 TDC7201 Time-to-Digital Converter
    4. 2.4 System Design Theory
      1. 2.4.1 Transimpedance Amplifier
        1. 2.4.1.1 Bandwidth
        2. 2.4.1.2 Stability Considerations
        3. 2.4.1.3 Noise Performance
      2. 2.4.2 Time-of-Flight Measurement
      3. 2.4.3 Simulations
        1. 2.4.3.1 Bandwidth Simulation
        2. 2.4.3.2 Noise Simulation
        3. 2.4.3.3 OPA858 Loop-Gain and Phase Margin Simulation
  8. 3Hardware, Software, Testing Requirements, and Test Results
    1. 3.1 Required Hardware and Software
      1. 3.1.1 Hardware
      2. 3.1.2 Software
    2. 3.2 Testing and Results
      1. 3.2.1 Test Setup
        1. 3.2.1.1 Getting Started: System Setup
          1. 3.2.1.1.1 Laser-Driver Setup
          2. 3.2.1.1.2 Receiver and Optical Setup
      2. 3.2.2 Test Results
        1. 3.2.2.1 Verification and Measured Performance
          1. 3.2.2.1.1 Pulse Response Measurements
            1. 3.2.2.1.1.1 Pulse Response Settling
            2. 3.2.2.1.1.2 Pulse Response vs Output Pulse Width
            3. 3.2.2.1.1.3 Rise and Fall Time
            4. 3.2.2.1.1.4 Overdriven Response
          2. 3.2.2.1.2 Time-of-Flight Test
          3. 3.2.2.1.3 Time-of-Flight Measurement Error Sources
  9. 4Design Files
    1. 4.1 Schematics
    2. 4.2 Bill of Materials
    3. 4.3 PCB Layout Recommendations
      1. 4.3.1 Layout Prints
    4. 4.4 Altium Project
    5. 4.5 Gerber Files
  10. 5Related Documentation
    1. 5.1 Trademarks
  11. 6About the Author
  12. 7Revision History

2.4.1.1 Bandwidth

The goal for the OPA858 transimpedance amplifier design is to achieve greater than 200 MHz of bandwidth with a gain of 10 kΩ. The maximum achievable transimpedance bandwidth of a circuit is a function of the amplifier gain bandwidth, gain, input capacitance, and feedback capacitance. The NR-7500 photodiode chosen for this design has an input capacitance of approximately 1.1 pF with a reverse bias voltage of 5 V. The photodiode capacitance coupled with the input 800-fF input capacitance of the OPA858 and the expected parasitic capacitance from the PCB yields a total input capacitance of approximately 2 pF. Using the transimpedance design theory stated in the Transimpedance Considerations for High-Speed Amplifiers application report, a Butterworth response with a quality factor (Q) of 0.707 yields a required feedback capacitance of approximately 100 fF and a bandwidth of 205 MHz. In order to achieve a higher bandwidth, relax the Q value to 0.95 to change the feedback capacitance to 75 fF and the bandwidth to 260 MHz. The higher Q value does cause peaking in the frequency response and overshoot in the pulse response, but with the edge-triggered nature of the TDC7201 measurement, the tradeoff of some overshoot allows a faster edge rate from the amplifier.