Файл: Audio Power Amp Design Handbook.pdf

Index

advantages of convention, 54–5
distortions, 55–8

gm-doubling, 107
Grounding system, 402
Group delay, 10

Hafler straight-wire differential test, 18
Half-amplifiers, 344
Harmonic-mean AB operation, 41
Hearing limits, 9–12
Heatsink:

designs, 414
for rectifier, 241
temperature sensing, 393

HF gain, 54
Hiraga, Jean, 9
Historical development, amplifiers, 30

Improvement factor, 45
Induction distortion, 57, 168
Input stage, 65

balance, 79
BJT/FET selection, 76
cascode configurations, 85
differential pair, 76
distortion, 64, 74–8
improving linearity, 82
noise reduction, 85
singleton, 76
slew-rate, 90

Instability, 222

HF, 222
LF, 223

Insulated-gate bipolar transistors

(IGBTs), 316

Integrated absolute error (IAE), 344
Integrated square error (ISE), 344

Johnson noise, 86
Junction-temperature estimator

subsystem, 350

with dynamics, 352

Lag compensation, 185
Large-signal non-linearity (LSN), 123

better output devices, 129

distortion, 127
doubled-output devices, 128
feed-forward diodes, 131
low loads, 132
mechanism, 127
output triples, 136
sustained beta devices, 129

Load-invariant design, 133
Loudspeakers:

cable inductance, 13–14
cable selection, 202
enhanced currents, 220
loading modelling, 210
single-speaker load, 214
two-way speaker loads, 218

Mains transformers, 239
Messenger, Paul, 9
Microphony, 16
Miller capacitor compensation, 63
Miller dominant pole creation, 184
Misinformation, technical, 5–6, 21
Mode-switching system, Class-A

amplifiers, 281

Model amplifiers, 70
Monobloc construction, 15
Motorboating see Instability, LF
Muting control, 386

N-rays, 8
Negative feedback (NFB), 15, 44–6

factor maximising, 57
maximising linearity, 57
misconceptions, 46–8
takeoff distortion, 65, 170

Nested feedback, 187
Nesting differentiating feedback loops,

41

Noise:

performance, 24
reduction, 24, 85

Non-switching amplifiers, 39

Open-loop:

bandwidth, 101
gain measurement, 68
linearity, 67

425

Index

Output networks, 190
Output stages, 106

alternative configurations, 103
CFP see Complementary feedback

pair (CFP) stages, 114

comparisons, 111
distortion, 123 and on
doubled, 128
emitter-folllower, 112
FET see Field effect transistor (FET)

output stages, 314

gm-doubling, 107
impedance, 192
improved, 296
low loads, 132
quasi-complementary, 119
quiescent conditions, 325
triple, 116, 136
use of inductors, 195

Overload protection, 372

by current limiting, 377
by dual-slope VI limiting, 381
by fuses, 373
by power supply shutdown, 340–41
by single-slope VI limiting, 38
catching diodes, 383
DC-offset, 384
electronic, 374
of output by thermal devices, 392
system simulation, 375

Parapsychology, 8
Performance requirements, 22–7
Phase delay, 10
Phase margin, 49
Phase shift, 15
Pole-splitting, 63
Power output capability, 22–3
Power supplies, 235

design, 15
design principles, 238
linear regulated, 236
mains transformers, 239
shutdown for overload protection,

392

simple unregulated, 235
switch-mode, 237

Power supply rejection ratio (PSRR),

242

Power supply-rail rejection, 241

design, 244
negative, 247
positive, 245

PCB and mechanical layout, 399

cooling requirements, 414
crosstalk, 397
grounding system, 404
layout details, 400
layout sequence, 403
mains transformers, 400
output device mounting, 398
plated-through-hole type, 399
power supply, 399
rail induction distortion, 398
semiconductor installation, 357–8
single/double-sided, 399
wiring layout, 416

Protection:

DC-offset, 384
overload see Overload protection
plotting locus, 376
thermal, 393

Psychoacoustical research, 7, 9–12
Push-pull action, 256, 259

Quad 405, 39
Quasi-complementary output, 119
Quiescent conditions, 152, 325
Quiescent current, 146

Class-A amplifiers, 263

Quiescent voltage, 152, 235

Rail decoupling distortion, 65, 165
Rail induction distortion, 347
Rectifiers, 240
Regulated power supplies, 236
Relay protection:

against DC offsets, 386
for system muting, 388

Reliability, 22
Reservoir ground, 404
Resistive loads, 209
Ripple, 242

Safe operating area (SOA), 266, 323,

375

426

Index

Safety requirements, 22, 420
Schottky diodes, 131, 298
Semiconductors:

failure modes, 371
installation, 416

Sensor position, 349
Sine wave signals, 13
Single-slope VI limiting, for overload

protection, 380

Slew rates, 48, 224

complications, 232
improving, 228
limiting, 225
measurement, 227
real-life limitations, 230
simulating, 228

Sound pressure level (SPL), 23
Speed see Slew rates
Standard amplifier performance, 71
Subjectivism, 6–9, 12–18
Switching distortion, 153
Switch-mode power supplies, 237
Sziklai pairs see Complementary

feedback pairs, 114

Temperature changes, ambient, 360
Temperature coefficient (tempco), 357

creating higher, 359
creating lower, 357

Temperature sensors, 393
Testing procedures, 418
Thermal behaviour:

basic compensation, 331
compensation accuracy, 332
EF stage compensation, 340
feedback/feedforward, 331
runaway, 30

sensor location, 349
simulation, 332

Thermal capacity, 333
Thermal cycling (failure mode), 372
Thermal distortion, 58, 66, 155
Thermal protection, 392
Thermal switch, 393
Tone-controls, 15
Total harmonic distortion (THD), 24–5

tests, 10

Transconductance, 78 et seq
Transformers, 220–21, 400
Translinear loop, 40–41
Trimodal amplifier, 269

biasing system, 280

Triple-based output, 116, 136
Two-pole compensation, 188, 312

Valve sound, 14
Variable-tempco bias generators, 357
Vbe multiplier, see Bias generator
Voltage amplifier stage (VAS), 31, 91

active load techniques, 95
balanced, 100
buffering, 99
distortion, 92, 95
enhancements, 97
linearising, 95
loading distortion, 99, 163
operation, 93

Wolf fence approach, supply-rail

rejection, 247

Zobel network, 194

427