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Audio Power Amplifier Design Handbook, 5th Edition

Book Description

This book is essential for audio power amplifier designers and engineers for one simple reason...it enables you as a professional to develop reliable, high-performance circuits. The Author Douglas Self covers the major issues of distortion and linearity, power supplies, overload, DC-protection and reactive loading. He also tackles unusual forms of compensation and distortion produced by capacitors and fuses.

Table of Contents

  1. Copyright
    1. Dedication
  2. Acknowledgments
  3. Preface to Fifth Edition
  4. Abbreviations
  5. 1. Introduction and General Survey
    1. The Economic Importance of Power Amplifiers
      1. Assumptions
      2. Origins and Aims
    2. The Study of Amplifier Design
    3. Misinformation in Audio
    4. Science and Subjectivism
      1. The Subjectivist Position
      2. A Short History of Subjectivism
      3. The Limits of Hearing
      4. Articles of Faith: The Tenets of Subjectivism
      5. The Length of the Audio Chain
      6. The Implications
      7. The Reasons Why
      8. The Outlook
      9. Technical Errors
    5. The Performance Requirements for Amplifiers
      1. Safety
      2. Reliability
      3. Power Output
      4. Frequency Response
      5. Noise
      6. Distortion
      7. Damping Factor
      8. Absolute Phase
    6. Amplifier Formats
    7. References
  6. 2. Power Amplifier Architecture and Negative Feedback
    1. Amplifier Architectures
      1. The Three-Stage Amplifier Architecture
      2. The Two-Stage Amplifier Architecture
      3. The four-Stage Amplifier Architecture
    2. Power Amplifier Classes
      1. Class-A
      2. Class-AB
      3. Class-B
      4. Class-C
      5. Class-D
      6. Class-E
      7. Class-F
      8. Class-G
      9. Class-H
      10. Class-S
      11. Variations on Class-B
      12. Error-Correcting Amplifiers
      13. Non-Switching Amplifiers
      14. Current-Drive Amplifiers
      15. The Blomley Principle
      16. Geometric Mean Class-AB
      17. Nested Differentiating Feedback Loops
    3. Amplifier Bridging
    4. Fractional Bridging
    5. AC- and DC-Coupled Amplifiers
      1. The Advantages of AC-Coupling
      2. The Advantages of DC-Coupling
    6. Negative Feedback in Power Amplifiers
      1. Some Common Misconceptions about Negative Feedback
      2. Amplifier Stability and NFB
      3. Maximizing the NFB
      4. Overall Feedback versus Local Feedback
      5. Maximizing Linearity before Feedback
    7. References
  7. 3. The General Principles of Power Amplifiers
    1. How a Generic Amplifier Works
    2. The Advantages of the Conventional
    3. The Distortion Mechanisms
      1. Distortion 1: Input Stage Distortion
      2. Distortion 2: VAS Distortion
      3. Distortion 3: Output Stage Distortion
      4. Distortion 4: VAS-Loading Distortion
      5. Distortion 5: Rail-Decoupling Distortion
      6. Distortion 6: Induction Distortion
      7. Distortion 7: NFB Take-Off Distortion
      8. Distortion 8: Capacitor Distortion
      9. Distortion 9: Magnetic Distortion
      10. Distortion 10: Input Current Distortion
      11. Distortion 11: Premature Overload Protection
    4. Nonexistent or Negligible Distortions
    5. The Performance of a Standard Amplifier
    6. Open-Loop Linearity and How to Determine It
    7. Direct Open-Loop Gain Measurement
    8. Using Model Amplifiers
    9. The Concept of the Blameless Amplifier
    10. References
  8. 4. The Input Stage
    1. The Role of the Input Stage
    2. Distortion from the Input Stage
    3. BJTs versus FETs for the Input Stage
      1. Advantages of the FET Input Stage
      2. Disadvantages of FET Input Stage
    4. Singleton Input Stage versus Differential Pair
    5. The Input Stage Distortion in Isolation
    6. Input Stage Balance
    7. The Joy of Current-Mirrors
    8. Better Current-Mirrors
    9. Improving Input Stage Linearity
    10. Further Improving Input Linearity
    11. Increasing the Output Capability
    12. Input Stage Cascode Configurations
    13. Double Input Stages
    14. Input Stage Common-Mode Distortion
    15. Input Current Distortion
    16. Input Stage Noise and How to Reduce It
    17. Noise Sources in Power Amplifiers
    18. Noise in Bipolar Transistors
    19. Reducing Input Transistor Noise
    20. Offset and Match: The DC Precision Issue
    21. The Input Stage and the Slew Rate
    22. Input Stage Conclusions
    23. References
  9. 5. The Voltage-Amplifier Stage
    1. Measuring VAS Distortion in Isolation
    2. VAS Operation
    3. VAS Distortion
    4. Linearizing the VAS: Active-Load Techniques
    5. VAS Enhancements
    6. Some More VAS Variations
    7. VAS Operating Conditions
    8. The Importance of Voltage Drive
    9. The Push–Pull VAS
    10. The High-Current Capability VAS
    11. Single Input Stages
    12. Double Input Stages
    13. Manipulating Open-Loop Bandwidth
    14. Conclusions
    15. References
  10. 6. The Output Stage
    1. Classes and Devices
    2. The Distortions of the Output
      1. Harmonic Generation by Crossover Distortion
      2. Comparing Output Stages
    3. The Emitter-Follower (EF) Output
    4. The Complementary Feedback Pair (CFP) Output
    5. Output Stages with Gain
    6. Quasi-complementary Outputs
    7. Triple-Based Output Configurations
      1. Triple-EF Output Stages
    8. Quadruple Output Stages
    9. Output Stage Distortions and their Mechanisms
    10. Large-Signal Distortion (Distortion 3a)
      1. The Load-Invariant Concept
      2. The LSN Mechanism
      3. Doubled Output Devices
      4. Better Output Devices
      5. Feedforward Diodes
      6. Trouble with Triples
      7. Loads Below 4 Ω
      8. Better 8 Ω Performance
      9. A Practical Load-Invariant Design
      10. More on Multiple Output Devices
      11. Load Invariance: Summary
    11. Crossover Distortion (Distortion 3b)
      1. Output Stage Quiescent Conditions
      2. An Experiment on Crossover Distortion
      3. Vq as the Critical Quiescent Parameter
    12. Switching Distortion (Distortion 3c)
    13. Thermal Distortion
    14. Thermal Distortion in a Power Amp IC
    15. Selecting an Output Stage
    16. Closing the Loop: Distortion in Complete Amplifiers
    17. Conclusions
    18. References
  11. 7. More Distortion Mechanisms
    1. Distortion 4: VAS-Loading Distortion
    2. Distortion 5: Rail-Decoupling Distortion
    3. Distortion 6: Induction Distortion
    4. Distortion 7: NFB Take-Off Point Distortion
    5. Distortion 8: Capacitor Distortion
    6. Distortion 9: Magnetic Distortion
    7. Distortion 10: Input Current Distortion
    8. Distortion 11: Premature Overload Protection
    9. Design Example – A 50 W Class-B Amplifier
    10. References
  12. 8. Compensation, Slew Rate, and Stability
    1. Frequency Compensation in General
    2. Dominant-Pole Compensation
    3. Lag Compensation
    4. Including the Output Stage: Output-Inclusive Miller Compensation
    5. Other Forms of Inclusive Compensation
    6. Two-Pole Compensation
    7. Stability and VAS-Collector-to-Ground Capacitance
    8. Nested Feedback Loops
    9. Output Networks
      1. Amplifier Output Impedance
      2. Minimizing Amplifier Output Impedance
      3. Zobel Networks
      4. Output Inductors
      5. The Output Inductor Value
      6. Cable Effects
    10. Crosstalk in Amplifier Output Inductors
      1. Coil Crosstalk Conclusions
    11. Reactive Loads and Speaker Simulation
      1. Resistive Loads
      2. Modeling Real Loudspeaker Loading
    12. Loudspeaker Loads and Output Stages
      1. Single-Speaker Load
      2. Two-Way Speaker Loads
    13. Enhanced Loudspeaker Currents
    14. Amplifier Instability
      1. HF Instability
      2. LF Instability
    15. Speed and Slew Rate in Audio Amplifiers
      1. The Basics of Amplifier Slew-Limiting
      2. Slew-Rate Measurement Techniques
      3. Improving the Slew Rate
      4. Simulating Slew-Limiting
      5. Slewing Limitations in Real Life
      6. Some Additional Complications
      7. Further Improvements and Other Configurations
    16. References
  13. 9. Power Supplies and PSRR
    1. Power-Supply Technologies
      1. Simple Unregulated Power Supplies
        1. Advantages
        2. Disadvantages
      2. Linear Regulated Power Supplies
        1. Advantages
        2. Disadvantages
      3. Switch-Mode Power Supplies
        1. Advantages
        2. Disadvantages
    2. A Devious Alternative to Regulated Power Supplies
    3. Design Considerations for Power Supplies
      1. Mains Transformers
        1. Transformer mounting
        2. Transformer specifications
        3. Electrical specifications
        4. Mechanical matters
          1. Safety issues
        5. Transformer evaluation
        6. Transformers and hum
      2. External Power Supplies
        1. Advantages
        2. Disadvantages
      3. Inrush Currents
        1. Inrush suppression by thermistor
        2. Inrush suppression by relay
      4. Fusing and Rectification
      5. RF Emissions from Bridge Rectifiers
      6. Relay Supplies
    4. Power-Supply Rail Rejection in Amplifiers
      1. A Design Philosophy for Supply-Rail Rejection
      2. Positive Supply-Rail Rejection
      3. Negative Supply-Rail Rejection
      4. Negative Sub-Rails
    5. References
  14. 10. Class-A Power Amplifiers
    1. An Introduction to Class-A
    2. Class-A Configurations and Efficiency
    3. Output Stages in Class-A
    4. Quiescent Current Control Systems
    5. A Novel Quiescent Current Controller
    6. A Class-A Design
    7. The Trimodal Amplifier
    8. Load Impedance and Operating Mode
    9. Efficiency
    10. Trimodal Biasing
    11. Class-A/AB Mode
    12. Class-B Mode
    13. The Mode-Switching System
    14. Thermal Design
    15. A Complete Trimodal Amplifier Circuit
    16. The Power Supply
    17. The Performance
    18. Further Possibilities
    19. References
  15. 11. Class-XD™: Crossover Displacement Technology
    1. The Crossover Displacement Principle
    2. Crossover Displacement Realization
    3. Circuit Techniques for Crossover Displacement
    4. A Complete Crossover Displacement Power Amplifier Circuit
    5. The Measured Performance
    6. The Effect of Loading Changes
    7. The Efficiency of Crossover Displacement
    8. Other Methods of Push–Pull Displacement Control
    9. Summary
      1. Advantages
      2. Disadvantages
    10. References
  16. 12. Class-G Power Amplifiers
    1. The Principles of Class-G
    2. Introducing Series Class-G
    3. Efficiency of Class-G
    4. Practicalities
    5. The Biasing Requirements
    6. The Linearity Issues of Series Class-G
    7. The Static Linearity
    8. Practical Class-G Design
    9. Controlling Small-Signal Distortion
    10. The Performance
    11. Deriving a New Kind of Amplifier: Class-A + C
    12. Adding Two-Pole Compensation
    13. Further Variations on Class-G
    14. References
  17. 13. Class-D Amplifiers
    1. History
    2. Basic Principles
    3. Technology
    4. Protection
    5. Output Filters
    6. Efficiency
  18. 14. FET Output Stages
    1. The Characteristics of Power FETs
    2. FET versus BJT Output Stages
      1. Advantages of FETs
      2. Disadvantages of FETs
    3. IGBTs
    4. Power FET Output Stages
    5. Power FETs and Bipolars: The Linearity Competition
    6. FETs in Class-A Stages
    7. References
  19. 15. Thermal Compensation and Thermal Dynamics
    1. Why Quiescent Conditions are Critical
    2. Accuracy Required of Thermal Compensation
    3. Basic Thermal Compensation
    4. Assessing the Bias Errors
    5. Thermal Simulation
    6. Modeling the EF Output Stage
    7. Modeling the CFP Output Stage
    8. The Integrated Absolute Error Criterion
    9. Improved Thermal Compensation for the EF Stage
    10. Improved Compensation for the CFP Output Stage
    11. A Better Sensor Position
    12. A Junction-Temperature Estimator
    13. A Junction Estimator with Dynamics
    14. Conclusions About the Simulations
    15. Power Transistors with Integral Temperature Sensors
    16. Variable-Tempco Bias Generators
      1. Creating a Higher Tempco
      2. Ambient Temperature Changes
      3. Creating a Lower Tempco
      4. Current Compensation
    17. Early Effect in Output Stages
    18. Thermal Dynamics by Experiment
      1. Crossover Distortion Against Time – Some Results
      2. More Measurements – Conventional and ThermalTrak
    19. References
  20. 16. The Design of DC Servos
    1. DC Offset Trimming
    2. DC Offset Control by Servo-Loop
    3. The Advantages of DC Servos
    4. Basic Servo Configurations
    5. Noise, Component Values, and the Roll-Off
    6. Non-Inverting Integrators
      1. The 2C Integrator
      2. The 1C Integrator
    7. Choice of Integrator Type
    8. Choice of Op-Amps
    9. Servo Authority
    10. Design of LF Roll-Off Point
    11. Servo Overload
    12. Servo Testing
    13. Performance Issues
    14. Multi-Pole Servos
  21. 17. Amplifier and Loudspeaker Protection
    1. Categories of Amplifier Protection
      1. Semiconductor Failure Modes
    2. Overload Protection
      1. Overload Protection by Fuses
      2. Electronic Overload Protection
      3. Plotting the Protection Locus
      4. Simple Current Limiting
      5. Single-Slope VI Limiting
      6. Dual-Slope VI Limiting
      7. VI Limiting and Temperature Effects
      8. Simulating Overload Protection Systems
      9. Testing the Overload Protection
      10. Speaker Short-Circuit Detection
    3. Catching Diodes
    4. DC Offset Protection
      1. DC Protection by Fuses
      2. Relay Protection and Muting Control
      3. Filtering for DC Protection
      4. The single RC filter
      5. The dual RC filter
      6. The second-order active filter
      7. Bidirectional DC Detection
      8. The conventional two-transistor circuit
      9. The one-transistor version
      10. The differential detector
      11. The Self detector
      12. Distortion in Output Relays
      13. Output Crowbar DC Protection
      14. Protection by Power-Supply Shutdown
    5. Thermal Protection
    6. Mains-Fail Detection
    7. Powering Auxiliary Circuitry
    8. References
  22. 18. Grounding, Cooling, and Layout
    1. Audio Amplifier PCB Design
      1. Crosstalk
      2. Rail Induction Distortion
      3. Mounting Output Devices on the Main PCB
        1. Advantages
        2. Disadvantages
      4. Single- and Double-Sided PCBs
      5. Power-Supply PCB Layout
      6. Power Amplifier PCB Layout Details
      7. The Audio PCB Layout Sequence
      8. Miscellaneous Points
    2. Amplifier Grounding
    3. Ground Loops: How They Work and How to Deal with Them
      1. Hum Injection by Mains Grounding Currents
      2. Hum Injection by Transformer Stray Magnetic Fields
      3. Hum Injection by Transformer Stray Capacitance
      4. Ground Currents Inside Equipment
      5. Balanced Mains Power
    4. Class-I and Class-II
      1. Warning
      2. Cooling
      3. Convection Cooling
        1. Heat-sink materials
        2. Heat-sink compounds
        3. Thermal washers
        4. Fan Cooling
        5. Fan control systems
        6. Fan failure safety measures
      4. Heat Pipes
    5. Mechanical Layout and Design Considerations
      1. Wiring Layout
      2. Semiconductor Installation
  23. 19. Testing and Safety
    1. Testing and Fault-Finding
    2. Powering up for the First Time
    3. Safety When Working on Equipment
    4. Warning
    5. Safety Regulations
    6. Electrical Safety
      1. Shocks from the Mains Plug
      2. Touch Current
      3. Case Openings
    7. Equipment Temperature and Safety
    8. Touching Hot Parts
    9. Instruction Manuals
  24. 20. Power Amplifier Input Systems
    1. External Signal Levels
    2. Internal Signal Levels
    3. The Choice of Op-Amps
    4. Unbalanced Inputs
    5. Balanced Interconnections
      1. Advantages
      2. Disadvantages
    6. Common-Mode Rejection Ratio
    7. Balanced Connectors
    8. Balanced Signal Levels
    9. Balanced Inputs: Electronic versus Transformer
    10. The Basic Balanced Input
    11. Common-Mode Rejection in the Basic Balanced Input
    12. The Practical Balanced Input
    13. Combined Unbalanced and Balanced Inputs
    14. Superbal Input
    15. Switched-Gain Balanced Inputs
    16. Variable-Gain Balanced Inputs
    17. High-Impedance Balanced Inputs
    18. The Inverting Two-Op-Amp Input
    19. The Instrumentation Amplifier
    20. Transformer Balanced Inputs
    21. Input Overvoltage Protection
    22. Noise and the Input System
    23. Low-Noise Balanced Inputs
    24. … And Quieter Yet
    25. Noise Reduction in Real Life
    26. Unbalanced and Balanced Outputs
    27. Unbalanced Outputs
    28. Ground-Canceling Outputs
    29. Balanced Outputs
    30. Quasi-Floating Outputs
    31. Transformer Balanced Outputs
    32. Using a Balanced Power Amplifier Interface
    33. References
  25. 21. Input Processing and Auxiliary Subsystems
    1. Ground-Lift Switches
    2. Phase Reversal Facility
    3. Gain Control
    4. Subsonic Filtering: High-Pass
    5. Ultrasonic Filtering: Low-Pass
    6. Combined Filters
    7. Electronic Crossovers
    8. Digital Signal Processing
    9. Signal-Present Indication
    10. Output Level Indication
    11. Signal Activation
    12. Twelve-Volt Trigger Activation
    13. Infrared Remote Control
    14. Other Amplifier Facilities
    15. References