A second-order class-D audio amplifier

Class-D audio amplifiers are particularly efficient, and this efficiency has led to their ubiquity in a wide range of modern electronic appliances. Their output takes the form of a high-frequency square wave whose duty cycle (ratio of on-time to off-time) is modulated at low frequency according to the audio signal. A mathematical model is developed here for a second-order class-D amplifier design (i.e., containing one second-order integrator) with negative feedback. We derive exact expressions for the dominant distortion terms, corresponding to a general audio input signal, and confirm these predictions with simulations. We also show how the observed phenomenon of “pulse skipping” arises from an instability of the analytical solution upon which the distortion calculations are based, and we provide predictions of the circumstances under which pulse skipping will take place, based on a stability analysis. These predictions are confirmed by simulations

1 V CMOS subthreshold log domain PDM

A new CMOS circuit strategy for very low-voltage Pulse-Duration Modulators (PDM) is proposed. Optimization of voltage supply scaling below the sum of threshold voltages is based on Instantaneous Log Companding processing through the MOSFET operating in weak inversion. A 1 V VLSI PDM circuit for very low-voltage audio applications such as Hearing Aids is presented, showing good agreement between simulated and experimental data.Comisión Interministerial de Ciencia y Tecnología TIC97-1159, TIC99-1084European Union 2306

Reliable solid-state circuits Semiannual report no. 2, Jun. 1 - Nov. 30, 1965

Pulse width modulator and other microminiaturized electronic equipment for space age application

A Power Efficient Audio Amplifier Combining Switching and Linear Techniques

Integrated Class D audio amplifiers are very power efficient, but require an external filter which prevents further integration. Also due to this filter, large feedback factors are hard to realise, so that the load influences the distortion- and transfer characteristics. The amplifier presented in this paper consists of a switching part that contains a much simpler filter, and a linear part that ensures a low distortion and flat frequency response. A 30W version was realised. The switching part of the amplifier was integrated in a BCD process. Together with a linear part and with a loudspeaker as load, it has a flat frequency response +/- 0.3dB, a dissipation that is up to 5 times lower than a traditional class AB audio amplifier, and a distortion of <0.02% over power and frequency range

Class-D Audio Amplifier using Sigma-Delta (ΣΔ) Modulator

Pulse width modulation and pulse density modulation are deemed to be main modulation techniques, even PDM could not emulate PWM, in terms of, basically, simplicity. PDM bitstream is encoded through sigma-delta modulation. Since sigma-delta modulation, compared to PWM, needs very high switching frequency and more complicated materials to compose circuits, it’s more difficult to design one. In this article we design a low-power class-D audio amplifier circuit where the analog signal is encoded into pulse density modulation (PDM) using a first-order sigma-delta (ΣΔ) modulator. The designed circuit is built using Orcad-PSpice and results are analyzed with Matlab. A second-order integrator, a voltage divider as a feedback loop are used to mitigate basically, THD and get high efficiency. The audio signal is passed to the EM speaker through a Butterworth low-pass filter. A low THD of less than 0.2 % is obtained comparing to similar circuits in the literature and a high efficiency of 92 % is achieved.

Transmission of Stereo Audio Signals with Lasers

An alternative method for transmitting audio signals via the use of laser technology was presented here. The primary focus of this document is on the audio amplifier subsystem including the design, simulation, and performance results. Simulations using the PSPICE computer simulation software were utilized to investigate the theoretical designs of the audio amplifier subsystem. The audio amplifier was examined in three junctures including the noise-canceling input stage, the high voltage gain cell, and the low impedance driver. Through the design procedure using theoretical calculations, simulations using PSPICE computer software, and examination of the finished product with an oscilloscope, the audio amplifier was greatly investigated and verified for desired functionality. In addition, the pulse-width modulation technique was examined and implemented with precision 555 timers in order to transmit audio signals via laser

Class D amplifier power stage with PWM feedback loop

This paper presents a Second-Order Pulse Width Modulation (PWM) feedback loop to improve Power Supply Rejection (PSR) of any open-loop PWM Class-D amplifiers (CDAs). PSR of the audio amplifier has always been a key parameter in mobile phone applications. In contrast to Class AB amplifiers, the poor PSR performance has always been the major drawback for CDAs with half-bridge connected power stage. The proposed PWM feedback loop is fabricated using GLOBALFOUNDRIES' (GF’s) 0.18 µm CMOS process technology. The measured PSR is more than 80 dB and the measured Total Harmonic Distortion (THD) is less than 0.04% with a 1 kHz input sinusoidal test tone

Methods of High-Fidelity, High-Efficiency Class-D Audio Amplification

Gallium nitride-based field effect transistors (FETs) have opened a path for full-frequency-range class-D audio amplifiers with low distortion and noise, thanks to their ability to switch at much higher frequencies than that of the upper range of human hearing. Compared to traditional silicon-based transistors, GaN-based transistors offer superior efficiencies, particularly at power levels below their maxima. Paired with an analog-to-digital converter, digital signal processor, and pulse-code modulation to pulse-width modulation converter, these transistors are used to design and implement a solid-state amplifier capable of generating 100 watts of output through speakers with an impedance of 8 ohms using a 1-volt line-level input. This digital signal processor, together with Analog Devices’s SigmaStudio development software, allows for equalization, filtering, and other modification of the signal in this design. Together, these equalization features, the use of GaN transistors, and various digital encoding methods are examined for their benefits in producing high-power, high-fidelity audio in small packages

An energy-efficient integration of a digital modulator and a Class-D amplifier

Energy consumption is always a key feature in devices powered by electric accumulators. The power amplifier is the most energy-demanding module in mobile devices, portable appliances, static transceivers, and even nodes used in underwater acoustic networks. These devices incorporate a modulator, typically a pulse-width modulation (PWM) and a class-D power amplifier, for higher efficiency. We propose a technique to integrate the modulator of a transmitter and PW-modulator of a class-D amplifier to improve the overall efficiency of the system. This integrated set operates as an up-converter, phase modulator (PM), and binary phase-shift keying (BPSK) modulator under certain conditions. The theoretical concept is verified using Matlab and a model is designed and simulated in Simulink. For validation purposes, an electronic circuit is built and tested using Multisim. The results obtained by simulations and circuit implementation show that the proposed integrated system is an energy-efficient and cost-effective solution compared to conventional techniques

Design of a Continuous-Time (CT) Sigma-Delta modulator for class D audio power amplifiers

Dissertação apresentada na Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa para obtenção do Grau de Mestre em Engenharia Electrotécnica e de Computadore