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Journal Article

Modulation and System Techniques in PWM and SDM Switching Amplifiers

Authors: Hawksford, Malcolm J.

Journal of the Audio Engineering Society · Volume 54 · Issue 3 · pp. 107–139 · March 2006

Abstract

Continuous- and discrete-time switching audio power amplifiers are studied both with and without feedback. Pulse-width modulation (PWM) and sigma–delta modulation (SDM) amplifier configurations are simulated and their interrelationship is described using linear phase modulation (LPM) and linear frequency modulation (LFM). Distortion generation encountered when applying negative feedback to PWM is demonstrated and strategies to improve linearity are presented. Recent innovations in SDM coding and output-stage topologies using pulse-shaping techniques are reviewed with emphasis on stable, low-distortion operation, especially under high-level signal excitation. A simplified low-latency variant of predictive SDM with step back is introduced, which together with dynamic compression of the state variables extends stable operation to a modulation depth of unity, thus allowing SDM to compete with PWM power amplifiers in terms of peak signal capability.

Details

Publication
Journal of the Audio Engineering Society
Volume
54
Issue
3
Pages
107–139
Publication date
March 6, 2006
Affiliation
University of Essex, Colchester, UK (See document for exact affiliation information.)
Type
Journal Article