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Design and analysis of a dual supply class H audio amplifier

Description
Efficiency of components is an ever increasing area of importance to portable applications, where a finite battery means finite operating time. Higher efficiency devices need to be designed that don't compromise on the performance that the consumer has come to expect. Class D amplifiers deliver on the goal of increased…

Efficiency of components is an ever increasing area of importance to portable applications, where a finite battery means finite operating time. Higher efficiency devices need to be designed that don't compromise on the performance that the consumer has come to expect. Class D amplifiers deliver on the goal of increased efficiency, but at the cost of distortion. Class AB amplifiers have low efficiency, but high linearity. By modulating the supply voltage of a Class AB amplifier to make a Class H amplifier, the efficiency can increase while still maintaining the Class AB level of linearity. A 92dB Power Supply Rejection Ratio (PSRR) Class AB amplifier and a Class H amplifier were designed in a 0.24um process for portable audio applications. Using a multiphase buck converter increased the efficiency of the Class H amplifier while still maintaining a fast response time to respond to audio frequencies. The Class H amplifier had an efficiency above the Class AB amplifier by 5-7% from 5-30mW of output power without affecting the total harmonic distortion (THD) at the design specifications. The Class H amplifier design met all design specifications and showed performance comparable to the designed Class AB amplifier across 1kHz-20kHz and 0.01mW-30mW. The Class H design was able to output 30mW into 16Ohms without any increase in THD. This design shows that Class H amplifiers merit more research into their potential for increasing efficiency of audio amplifiers and that even simple designs can give significant increases in efficiency without compromising linearity.
ContributorsPeterson, Cory (Author) / Bakkaloglu, Bertan (Thesis advisor) / Barnaby, Hugh (Committee member) / Kiaei, Sayfe (Committee member) / Arizona State University (Publisher)
Created2013
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Modeling & analysis of a closed loop class D audio amplifier for PSR improvement

Description
Class D Amplifiers are widely used in portable systems such as mobile phones to achieve high efficiency. The demands of portable electronics for low power consumption to extend battery life and reduce heat dissipation mandate efficient, high-performance audio amplifiers. The high efficiency of Class D amplifiers (CDAs) makes them particularly…

Class D Amplifiers are widely used in portable systems such as mobile phones to achieve high efficiency. The demands of portable electronics for low power consumption to extend battery life and reduce heat dissipation mandate efficient, high-performance audio amplifiers. The high efficiency of Class D amplifiers (CDAs) makes them particularly attractive for portable applications. The Digital class D amplifier is an interesting solution to increase the efficiency of embedded systems. However, this solution is not good enough in terms of PWM stage linearity and power supply rejection. An efficient control is needed to correct the error sources in order to get a high fidelity sound quality in the whole audio range of frequencies. A fundamental analysis on various error sources due to non idealities in the power stage have been discussed here with key focus on Power supply perturbations driving the Power stage of a Class D Audio Amplifier. Two types of closed loop Digital Class D architecture for PSRR improvement have been proposed and modeled. Double sided uniform sampling modulation has been used. One of the architecture uses feedback around the power stage and the second architecture uses feedback into digital domain. Simulation & experimental results confirm that the closed loop PSRR & PS-IMD improve by around 30-40 dB and 25 dB respectively.
ContributorsChakraborty, Bijeta (Author) / Bakkaloglu, Bertan (Thesis advisor) / Garrity, Douglas (Committee member) / Ozev, Sule (Committee member) / Arizona State University (Publisher)
Created2012
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Class D audio amplifier design with power supply noise cancellation

Description
In this thesis, a digital input class D audio amplifier system which has the ability

to reject the power supply noise and nonlinearly of the output stage is presented. The main digital class D feed-forward path is using the fully-digital sigma-delta PWM open loop topology. Feedback loop is used to suppress…

In this thesis, a digital input class D audio amplifier system which has the ability

to reject the power supply noise and nonlinearly of the output stage is presented. The main digital class D feed-forward path is using the fully-digital sigma-delta PWM open loop topology. Feedback loop is used to suppress the power supply noise and harmonic distortions. The design is using global foundry 0.18um technology.

Based on simulation, the power supply rejection at 200Hz is about -49dB with

81dB dynamic range and -70dB THD+N. The full scale output power can reach as high as 27mW and still keep minimum -68dB THD+N. The system efficiency at full scale is about 82%.
ContributorsBai, Jing (Author) / Bakkaloglu, Bertan (Thesis advisor) / Arizona State University (Publisher)
Created2015
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Rock-dwelling Spiny Lizards Take Advantage of Human-disturbed Habitat in the Trans-Mexican Volcanic Belt

Description
Human land use and land cover change alter key features of the landscape that may favor habitat selection by some species. Lizards are especially sensitive to these alterations because they rely on their external environment for regulating their body temperature. However, because of their diverse life-history traits and strategies, some…

Human land use and land cover change alter key features of the landscape that may favor habitat selection by some species. Lizards are especially sensitive to these alterations because they rely on their external environment for regulating their body temperature. However, because of their diverse life-history traits and strategies, some are able to respond well to disturbance by using their habitat in various ways. To understand how they use their habitat and how human modifications may impact their ability to do this, biologists must identify where they occur and the habitat characteristics on which they depend. Therefore, I used species occupancy modeling to determine (1) whether disturbance predicts the presence of two sympatric congeneric (species of the same genus) lizard species Sceloporus grammicus and S. torquatus, and (2) which habitat characteristics are essential for predicting their occupancy and detection. I focused my study in central Mexico, a region of prevalent land use and land cover change. Here, I conducted visual encounter and habitat surveys at 100 1-hectare sites during the spring of 2019. I measured vegetation and ground cover, average tree diameter, and abundance of refuges. I recorded air temperature, relative humidity, and elevation. I summarized sites as either undisturbed or disturbed, based on the presence of human development. I also summarized sites by ecosystem type, desert or forest, based on vegetation composition (i.e., desert-adapted vs. non-desert-adapted plants), evidence of remnant forest, air temperature, and relative humidity. I found that S. torquatus was more likely to be present in disturbed habitat, whereas S. grammicus was more likely to be present in areas with leaf litter, tree cover, and woody debris. S. torquatus was twice as likely to be detected in forests than deserts, and S. grammicus was more likely to be detected at sites with high elevation and high relative humidity, low temperature, and herbaceous and grass cover. These results emphasize the utility of species occupancy modeling for estimating detection and occupancy in dynamic landscapes.
ContributorsFlores, Jennifer (Author) / Martins, Emília P. (Thesis advisor) / Bateman, Heather L (Thesis advisor) / Zuniga-Vega, J. Jaime (Committee member) / Arizona State University (Publisher)
Created2020
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Examining the Impacts of Ecotourism on Humpback Whales (Megaptera novaeangliae) in Panama

Description
Cetacean-based ecotourism is a popular activity and an important source of revenue for many countries. Whale watching, a subset of cetacean-based ecotourism, is vital to supporting conservation efforts and provides numerous benefits to local communities including educational opportunities and job creation. However, the sustainability of whale-based ecotourism depends on the…

Cetacean-based ecotourism is a popular activity and an important source of revenue for many countries. Whale watching, a subset of cetacean-based ecotourism, is vital to supporting conservation efforts and provides numerous benefits to local communities including educational opportunities and job creation. However, the sustainability of whale-based ecotourism depends on the behavior and health of whale populations and is therefore vital that ecotourism industries consider the impact their activities have on whale reproductive behavior. To address this statement, behavioral data (e.g. direction change, breaching, slap behaviors, diving, and spy hops) were collected from humpback whales (Megaptera novaeangliae) in Las Perlas Archipelago off the Pacific coast of Panama to determine if vessel presence had an influence on whale behaviors. Studies were recorded during their breeding season from August through September in 2019. Based on 47 behavioral observations, higher boat density corresponded with humpback whales changing direction which is believed to be a sign of disturbance. This result is important given Panamanian regulations implemented on February 13 of 2007 prohibit whale-based tourism from disturbing whales, which is measured as changes in behavior. Because there is no systematic monitoring of whale watching activity to enforce the regulations, there is currently little compliance among tour operators. The integration of animal behavior research into management planning will result in more effective regulation and compliance of conservation policies.
ContributorsAmrein, Arielle (Author) / Gerber, Leah R. (Thesis advisor) / Guzman, Hector M (Committee member) / Polidoro, Beth (Committee member) / Arizona State University (Publisher)
Created2020
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Assessing the Response of Macroinvertebrate Communities to River Flow Dynamics in the Sonoran Desert

Description

Climate change is causing hydrologic intensification globally by increasing both the frequency and magnitude of floods and droughts. While environmental variation is a key regulator at all levels of ecological organization, such changes to the hydrological cycle that are beyond the normal range of variability can have strong impacts on…

Climate change is causing hydrologic intensification globally by increasing both the frequency and magnitude of floods and droughts. While environmental variation is a key regulator at all levels of ecological organization, such changes to the hydrological cycle that are beyond the normal range of variability can have strong impacts on stream and riparian ecosystems within sensitive landscapes, such as the American Southwest. The main objective of this study was to investigate how anomalous hydrologic variability influences macroinvertebrate communities in desert streams. I studied seasonal changes in aquatic macroinvertebrate abundances in eleven streams that encompass a hydrologic gradient across Arizona’s Sonoran Desert. This analysis was coupled with the quantification and assessment of stochastic hydrology to determine influences of flow regimes and discrete events on invertebrate community composition. I found high community variability within sites, illustrated by seasonal measures of beta diversity and nonmetric multidimensional scaling (NMDS) plots. I observed notable patterns of NMDS data points when invertebrate abundances were summarized by summer versus winter surveys. These results suggest that there is a difference within the communities between summer and winter seasons, irrespective of differences in site hydroclimate. Estimates of beta diversity were the best metric for summarizing and comparing diversity among sites, compared to richness difference and replacement. Seasonal measures of beta diversity either increased, decreased, or stayed constant across the study period, further demonstrating the high variation within and among study sites. Regime shifts, summarized by regime shift frequency (RSF) and mean net annual anomaly (NAA), and anomalous events, summarized by the power of blue noise (Maximum Blue Noise), were the best predictors of macroinvertebrate diversity, and thus should be more widely applied to ecological data. These results suggest that future studies of community composition in freshwater systems should focus on understanding the cause of variation in biodiversity gradients. This study highlights the importance of considering both flow regimes and discrete anomalous events when studying spatial and temporal variation in stream communities.
ContributorsSainz, Ruby (Author) / Sabo, John L (Thesis advisor) / Grimm, Nancy (Committee member) / Stampoulis, Dimitrios (Committee member) / Arizona State University (Publisher)
Created2021