The thesis deal with the design and construction of single cluster of apparatus which can serve as a signal source for wavefield synthesis. Apparatus can be controlled remotely by Ethernet interface. Thesis contains theoretical analyses of speaker system, class D amplifier, digital to analog conversion, digital format of acoustic data ADAT and Ethernet interface. Conceptual design of cluster and description of constructed module is concerned.

This text analyzes characteristics of audio power amplifiers in class D. The emphasis is placed on more detailed analysis of modulators, drivers, connection topology of power transistors. In the next section of text are analyzed available integrated circuits of power amplifiers in class D which are manufactured by world producers. The last part describes design of all parts of amplifier in class D with discrete components and also of power supplies. According to the plans, the individual parts are made. All parts are tested by measurements and results are evaluated.

<p>Sal/Hall D, Forum, KTH-ICT, Isafjordsgatan 39, Kista</p>

Thesis (PhD (Electrical and Electronic Engineering))--University of Stellenbosch, 2009. / Although the Class D topology offers several advantages, its use in audio amplification has previously been limited by the lack of competitiveness in fidelity compared to its linear counterparts. During the past decade, technological advances in semiconductor technology have awakened new interest since competitive levels of distortion could now be achieved. The output stage of such an amplifier is the primary limiting factor in its performance. In this dissertation, four non-ideal effects existing in this stage are identified and mathematically analysed. The analytical analysis makes use of a well-established mathematical model, based on the double Fourier series method, to model the imperfections introduced into a naturally sampled pulsewidth modulated waveform. The analysis is complemented by simulation using a strategy based on Newton’s numerical method. The theory is verified by a comparison between the analytical-, simulated- and experimental results.

Throughout this thesis, we studied the biochemical and structural impact of the essential residues on the activity of class D beta-lactamases. The production of these enzymes plays a major role in the bacterial resistance. Our work is subdivided in two parts : the study of the post-translational modification of lysine 70 and the screening of new potential inhibitors for the class D β-lactamases. The first part concerns the impact of the residues tryptophan 154 and valine 117 located in the hydrophobic core. Our data indicate that the mutation of tryptophan 154 in alanine or glycine lead to a large decrease of the catalytic efficiencies of the beta-lactamase. The apo-enzyme structures of these mutants show that the lysine 70 is not carboxylated. This absence of carboxylate group induces a modification of the hydrogen network of the active site. The analysis of the complex structure of W154A-benzylpenicillin demonstrates that the deacylation step is clearly the most affected by the mutation. The mutation of tryptophan 154 in histidine leads to a slight decrease of catalytic efficiencies because the imidazol group of histidine mimics the indole group of tryptophan 154. The apo-enzyme structure reveals that lysine 70 is partially carboxylated and stabilized by an hydrogen bond between the carboxylate group and the imidazol group. In the case of the V117T mutant, a strong increase of the catalytic constant values is observed at 50 mM in NaHCO3. The structure of this mutant at pH 8.0 shows that the lysine 70 is partially carboxylated in the monomer A. The determination of individual rate constants of acylation and deacylation steps indicates that the deacylation is the limiting step for the class D beta-lactamase. The k2/k3 ratio is similar between the V117T mutant and the wild-type enzyme. The mutation of lysine 70 in alanine or cysteine leads to a large decrease of the deacylation constants inducing a poorly efficient enzyme. The obtaining of the K70C-Ampicillin complex by X-ray cristallography and the trapping of acyl-enzyme by reaction with fluorescent ampicillin are supplemental proofs that the deacylation step is the limiting rate. By crystallographic and kinetic studies, we demonstrate that the chloride inhibition of the class D beta-lactamases is due to a competition between the carboxylate group of lysine 70 and the chloride ions. At high concentration in bicarbonate, this inhibition is abolished for the wild-type enzyme. The second part of this work concerns the screening of the citrate and aminophosphonate derivated molecules for the class D beta-lactamases. In the case of OXA-10, a citrate molecule is strongly stabilized by hydrogen bonds in the active site. The benzyl esters derivatives of citrate inhibits OXA-10(KI = 20 µM) but the hydrophobic substituents are necessary to obtain a good inhibition.

abstract: Pulse Density Modulation- (PDM-) based class-D amplifiers can reduce non-linearity and tonal content due to carrier signal in Pulse Width Modulation - (PWM-) based amplifiers. However, their low-voltage analog implementations also require a linear- loop filter and a quantizer. A PDM-based class-D audio amplifier using a frequency-domain quantization is presented in this paper. The digital-intensive frequency domain approach achieves high linearity under low-supply regimes. An analog comparator and a single-bit quantizer are replaced with a Current-Controlled Oscillator- (ICO-) based frequency discriminator. By using the ICO as a phase integrator, a third-order noise shaping is achieved using only two analog integrators. A single-loop, singlebit class-D audio amplifier is presented with an H-bridge switching power stage, which is designed and fabricated on a 0.18 um CMOS process, with 6 layers of metal achieving a total harmonic distortion plus noise (THD+N) of 0.065% and a peak power efficiency of 80% while driving a 4-ohms loudspeaker load. The amplifier can deliver the output power of 280 mW. / Dissertation/Thesis / Ph.D. Electrical Engineering 2011

This work describes the design of audio amplifiers operating in switching mode. The first part describes basic principles of the power stage switching concept. There is described differences between classes of amplifiers according to technology. The second larger part includes design and construction of the switching amplifiers. Design is implemented, including the preamplifier and power supply. Power supply works in switching mode. The measured parameters of the proposed facility are given in the last part.

The aim of this work was to design and construct a simple audio amplifier, which would be based of involvement and components used in switching power sources on the maximum degree (for example from usual ATX sources for computer). The main motivation for development is the existence of many old sources that do not use and big interest of users for the construction of home audio amplifiers for small and medium power. Amplifiers based on switching power sources with greater efficiency and less weight than comparable classic amplifiers (working in classes A, B or AB). Their disadvantage is the complicated design and introduction of distortion and spurious signals to the amplified signal. This work will be described a design of simple amplifier, which will minimize these negative effects. For shortcomings and wrong parameters this proposed involvement will be eventually described and implemented design of amplifier in class D.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The objectives of this work and present a class D amplifiers and full-bridge class D amplifier used to supply one or more high pressure sodium lamps (HPS). In this work, the lamps are feed a synthesized waveform to avoid acoustic resonance. The waveform injected contains a fundamental frequency around 1kHz and its third harmonic. The injection waveform synthesized prevents acoustic resonance the spread power the lamp in spectrum frequency. The ease of control of Class D amplifiers ensures a waveform without major changes in relation to entry. The control strategy and operation of the amplifiers stages have been shown. Studies were presented the strategies used to avoid acoustic resonance and detailed analysis of the injection waveform synthesized. The results of the simulations and practical results obtained were presented. / O objetivo deste trabalho é apresentar a utilização de amplificadores classe D e um nova topologia de amplificador full-bridge, classe D, para acionar uma ou mais lâmpadas de Alta Pressão de Sódio (HPS). As lâmpadas são alimentadas por uma forma de onda sintetizada para evitar a ressonância acústica, onde a forma de onda contém uma frequência fundamental de 1kHz e sua terceira harmônica. Essa técnica é utilizada para evitar o surgimento da ressonância acústica, espalhando no espectro da frequência a potência distribuída na lâmpada. A facilidade do controle dos amplificadores classe D garante uma forma de onda sem grandes variações em relação à entrada. A estratégia de controle e as etapas de funcionamento dos amplificadores são apresentadas juntamente ao estudo das técnicas utilizadas para evitar a ressonância acústica e a análise detalhada sobre a injeção da forma de onda sintetizada. Os resultados das simulações e os resultados práticos obtidos foram apresentados. / Doutor em Ciências

Orientadores: Jose Antenor Pomilio, Saulo Finco / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-09T03:34:05Z (GMT). No. of bitstreams: 1 Mioni_DanielPasti_M.pdf: 1903299 bytes, checksum: 7343c6fb1cd22aa8df8654d5b9b51852 (MD5) Previous issue date: 2007 / Resumo: Desenvolvemos um amplificador de áudio classe D baseado em moduladores S-?, destinado a aparelhos auditivos, a maioria dos quais utiliza baterias de 1,1V e necessita ter baixo consumo de corrente. Neste trabalho os amplificadores e comparadores foram construídos com inversores CMOS, pois um destes inversores, alimentado com uma tensão de 1,1V, pode consumir uma corrente CC tão baixa quanto 400nA, dependendo das dimensões, e proporcionar alto ganho de tensão quando polarizado em sua região linear de operação. Por estes motivos, podem substituir com vantagem amplificadores operacionais e comparadores em algumas aplicações. Um protótipo deste circuito foi implementado com tecnologia CMOS 0,35µm e alcançou um rendimento de 90% / Abstract: This thesis presents the design of a firstorder S-? audioband power amplifier optimized for hearing aid (HA) amplification. The majority of HAs use a 1.1V battery and require very low current consumption to improve battery life. This work made use of amplifiers and comparators based on CMOS inverters because such an inverter, with a 1.1V battery, can operate on a current as low as 400nA, depending on its dimensions, and provide high voltage gain when biased in their linear region. For these reasons, they can substitute with advantage operational amplifiers in some applications. A prototype of this circuit was implemented in a monolithic chip using 0.35µm CMOS technology and achieved 90% of power efficiency / Mestrado / Eletrônica, Microeletrônica e Optoeletrônica / Mestre em Engenharia Elétrica