SBOS855E January   2017  – December 2022 OPA1677 , OPA1678 , OPA1679

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and 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: OPA1677
    5. 6.5 Thermal Information: OPA1678
    6. 6.6 Thermal Information: OPA1679
    7. 6.7 Electrical Characteristics
    8. 6.8 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 Phase Reversal Protection
      2. 7.3.2 Electrical Overstress
      3. 7.3.3 EMI Rejection Ratio (EMIRR)
        1. 7.3.3.1 EMIRR IN+ Test Configuration
    4. 7.4 Device Functional Modes
      1. 7.4.1 Operating Voltage
  8. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 Capacitive Loads
    2. 8.2 Typical Applications
      1. 8.2.1 Phantom-Powered Preamplifier for Piezo Contact Microphones
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
          1. 8.2.1.2.1 Power Supply
          2. 8.2.1.2.2 Input Network
          3. 8.2.1.2.3 Gain
          4. 8.2.1.2.4 Output Network
        3. 8.2.1.3 Application Curves
      2. 8.2.2 Phono Preamplifier for Moving Magnet Cartridges
      3. 8.2.3 Single-Supply Electret Microphone Preamplifier
      4. 8.2.4 Composite Headphone Amplifier
      5. 8.2.5 Differential Line Receiver With AC-Coupled Outputs
    3. 8.3 Power Supply Recommendations
    4. 8.4 Layout
      1. 8.4.1 Layout Guidelines
        1. 8.4.1.1 Power Dissipation
      2. 8.4.2 Layout Example
  9. 9 Device and Documentation Support
    1. 9.1 Device Support
      1. 9.1.1 Development Support
        1. 9.1.1.1 PSpice® for TI
        2. 9.1.1.2 TINA-TI™ Simulation Software (Free Download)
        3. 9.1.1.3 DIP-Adapter-EVM
        4. 9.1.1.4 DIYAMP-EVM
        5. 9.1.1.5 TI Reference Designs
        6. 9.1.1.6 Filter Design Tool
    2. 9.2 Documentation Support
      1. 9.2.1 Related Documentation
    3. 9.3 Receiving Notification of Documentation Updates
    4. 9.4 Support Resources
    5. 9.5 Trademarks
    6. 9.6 Electrostatic Discharge Caution
    7. 9.7 Glossary
  10. 10Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information
8.2.1.2.4 Output Network

The audio signal is ac-coupled onto the microphone signal lines through capacitors C5 and C6. The value of capacitors C5 and C6 are determined by the low-frequency design requirements and the input impedance of the microphone preamplifier that connect to the output of the circuit. Equation 9 shows an approximation of the capacitor value requirements, and neglects the effects of R10, R11, R12, and R13 on the frequency response. The microphone preamplifier input impedance (RIN_MIC) uses a typical value of 4.4 kΩ for the calculation.

Equation 9. GUID-1E3BF848-A935-47F0-94EA-786145DC0286-low.gif

For simplicity, the same 22-μF capacitors selected for the power supply filtering are selected for C5 and C6 to satisfy Equation 9. At least 50-V rated capacitors must be used for C5 and C6. If polarized capacitors are used, the positive terminal must be oriented towards the microphone preamplifier. Resistors R10 and R11 isolate the op amp outputs from the capacitance of long cables that can cause instability. R12 and R13 discharge ac-coupling capacitors C4 and C5 when phantom power is removed.