ВУЗ: Казахская Национальная Академия Искусств им. Т. Жургенова
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Synopsis
Slewing limitations in real life
Some additional complications
Further improvements and other configurations
Chapter 8 Power supplies and PSRR
Power supply technologies
Simple unregulated supplies
Linear regulated supplies
Switch-made power supplies
Design considerations for unregulated supplies
Mains transformers
Fusing and rectification
RF emissions from bridge rectifiers
Power supply-rail rejection
A design philosophy for rail rejection
Positive supply-rail rejection
Negative supply-rail rejection
Chapter 9 Class-A power amplifiers
An introduction to Class-A
Class-A configurations and efficiency
Output stages in Class-A
Quiescent current control systems
A novel quiescent current controller
A complete Class-A power amplifier
Trimodal power amplifiers
Load impedance and operating mode
Efficiency
On Trimodal biasing
Class-A/AB mode
Class-B mode
The mode-switching system
Thermal design
A complete Trimodal power amplifier
The power supply
The performance
Further possibilities
Chapter 10 Class-G power amplifiers
The principles of Class-G
Introducing series Class-G
Efficiency of Class-G
Practicalities
The biasing requirements
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Synopsis
The linearity issues of series Class-G
The static linearity
Practical Class-G design
Controlling small-signal distortion
The performance
Deriving a new kind of amplifier: Class-A + C
Adding two-pole compensation
Further variations on Class-G
Chapter 11 FET output stages
The characteristics of power FETs
Power FETs versus bipolar transistors (BJTs)
Insulated-Gate Bipolar Junction Transistors (IGBTs)
Power FET output stages
The FET/bipolar linearity comparison
FETs in Class-A stages
Chapter 12 Thermal compensation and thermal
dynamics
Why Class-B quiescent conditions are critical
The accuracy required
Basic thermal compensation
Assessing the bias errors
Thermal simulation
Modelling the EF output stage
Modelling the CFP output stage
The integrated absolute error criterion
Improved thermal compensation: The emitter-follower stage
Improved thermal compensation: The CFP output stage
A better CFP sensor position
A junction-temperature estimator
A junction estimator with dynamics
Conclusion
Variable-tempco bias generators
Creating a higher tempco
Ambient temperature changes
Creating a lower tempco
Current compensation
Thermal dynamics in reality
Early effect in output stages
Chapter 13 Amplifier and loudspeaker protection
Categories of amplifier protection
Semiconductor failure modes
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Synopsis
Overload protection
Fusing
Electronic protection
Plotting the protection locus
Simple current-limiting
Single-slope VI limiting
Dual-slope VI limiting
Simulating overload protection
Catching diodes
DC-offset protection
Fusing
Relay protection and muting output control
Distortion in output relays
Output crowbar DC protection
Protection by power-supply shutdown
Thermal protection
Powering auxiliary circuitry
Chapter 14 Grounding and practical matters
Audio Amplifier PCB design
Crosstalk
Rail induction distortion
The mounting of output devices
Single and double-sided PCBs
Power supplies
Power amplifier PCB layout details
The audio PCB layout sequence
Miscellaneous points
Amplifier grounding
Ground loops: how they work and how to deal with them
Class I and Class II
Mechanical layout and design
Convection cooling
Cooling
Mains transformers
Wiring layout
Semiconductor installation
Chapter 15 Testing and safety
Testing and fault-finding
Safety requirements
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I wish to dedicate this book to my parents Russell and Evelyn, and
to all the friends and colleagues who have given me help,
information and encouragement while I was engaged in its writing.
In particular I want to acknowledge the active assistance and
collaboration of Gareth Connor in the quest for the perfect
amplifier, and the fortitude of Peter King in enduring many rambling
expositions of my latest thoughts on the subject.
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Preface
The design of power amplifiers exerts a deep fascination all of its own in
both amateur and professional circles. The job they do is essentially simple,
but making a reliable high-performance circuit to do it well is surprisingly
difficult, and involves delving into all kinds of byways of electronics.
Perhaps this paradox is at the root of the enduring interest they generate.
Reliable information on power amplifier design is hard to find, but in this
book, I hope to fill at least some of that need.
It is notable how few aspects of amplifier design have received serious
scientific investigation. Much of this book is the result of my own research,
because the information required simply was not to be found in the
published literature.
In the course of my investigations, I was able to determine that power
amplifier distortion, traditionally a difficult and mysterious thing to grapple
with, was the hydra-headed amalgamation of seven or eight mechanisms,
overlaying each other and contributing to a complex result. I have evolved
ways of measuring and minimising each distortion mechanism separately,
and the result is a design methodology for making Class-B or Class-A
amplifiers with distortion performance so good that two or three years ago
it would have been regarded as impossible. The methodology gives
pleasingly reliable and repeatable results with moderate amounts of
negative feedback, and insignificant added cost. It is described and
explained in detail here.
This leads to the concept of what I have called a Blameless amplifier, which
forms a benchmark for distortion performance that varies surprisingly little,
and so forms a well-defined point of departure for more ambitious and
radical amplifier designs. The first of these I have undertaken is the Trimodal
amplifier (so-called because it can work in any of the modes A, AB and B,
as the situation requires) which is fully described in Chapter 9.
Apart from the major issue of distortion and linearity in power amplifier
design, I also cover more mundane but important matters such as reliability,
power supplies, overload and DC-protection, and so on. In addition there
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