Matching Items (6)
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- Genre: Masters Thesis
- Creators: Arizona State University
- Creators: Chakraborty, Bijeta
- Creators: Peterson, Cory
- Member of: ASU Electronic Theses and Dissertations
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, 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
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 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
Description
Medical policies, practices, and definitions do not exist solely in the clinical realm; they show up in the lived experiences of patients. This research examines how people with the chronic illness called myalgic encephalomyelitis (ME) define their own illness experiences. They have situated knowledge about their illness onset, search for care, and clinical encounters. Their knowledge complicates and challenges the existing norms in clinical practice and medical discourse, as the experience of searching for care with ME reveals weaknesses in a system that is focused on acute care. Patient narratives reveal institutional patterns that obstruct access to medical care, such as disbelief from clinicians and lack of training in chronic illness protocols. They also reveal patterns in physician behavior that indicate the likelihood of receiving effective care. These patient narratives serve as a basis for continued examination of ME as well as further reconstruction of medical practice and procedure.
ContributorsCutler, Carmen (Author) / Oliverio, Annamaria (Thesis advisor) / Mann, Annika (Thesis advisor) / Behl, Natasha (Committee member) / Arizona State University (Publisher)
Created2019
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 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%.
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
An investigation of academic achievement and achievement motivation in children with cystic fibrosis
Description
Cystic Fibrosis, one of the most severe childhood life-shortening illnesses, places demands on a child's life conceivably interfering with his or her academic success. It is possible that the medically related activities in which individuals with CF partake interfere with academic activities and the motivation, specifically beliefs, expectancies, and values held, toward those activities. These issues encouraged the investigation of academic achievement and achievement motivation in children with CF through exploration of three research questions. Question one concerns differences in academic achievement between children with CF and a healthy comparison group for 1) reading and 2) math. Question two explored differences in aspects of motivation including ability beliefs, outcome expectancies, and task values between the groups for the two academic subjects. Finally, question three examined the relationship between motivational components and academic achievement. Evidence is provided for differences in math achievement between the two groups. Differences in motivation between children with CF and healthy children remain unsubstantiated.
ContributorsHall, Morgan (Author) / Gorin, Joanna (Thesis advisor) / Wodrich, David (Committee member) / Husman, Jenefer (Committee member) / Arizona State University (Publisher)
Created2010
Description
The prevalence of chronic illness among children in the United States is on the rise (CDC, 2014). Having a child with a chronic illness can be a substantial source of stress for a couple, including physical, emotional, and financial demands of caregiving as well as difficult decision-making regarding the child’s health (Mayo Clinic, 2015). Coping with such stressors can have a negative effect on the couple’s well-being, and, if not managed within the relationship, can lead to increased negative outcomes for both partners. Partners can, however, learn to cope with stress by engaging in the coping process together with dyadic coping (DC). Couples can engage in positive (i.e., supportive emotion-focused, supportive problem-focused, and delegated) or negative forms of DC. DC has been shown to mitigate stress for couples, while increasing reports of individual well-being (IWB) and relational well-being (RWB), but it has not been examined in the context of couples with a child with a chronic illness.
To bridge this gap, the present study examined how couples cope with general stress as well as stress associated with their child’s diagnosis of a chronic illness (CI-related stress) and whether positive DC and negative DC moderate association between stress (general stress and CI-related stress) and well-being (IWB and RWB). Consistent with hypotheses, there were significant main effects of both types of stress (general and CI-related stress) on both types of well-being (IWB and RWB). Contrary to the hypotheses that DC (positive DC and negative DC) would moderate the associations between both types of stress and both types of well-being, only one significant interaction was found between CI-related stress and negative DC on IWB. Implications of these findings are discussed.
To bridge this gap, the present study examined how couples cope with general stress as well as stress associated with their child’s diagnosis of a chronic illness (CI-related stress) and whether positive DC and negative DC moderate association between stress (general stress and CI-related stress) and well-being (IWB and RWB). Consistent with hypotheses, there were significant main effects of both types of stress (general and CI-related stress) on both types of well-being (IWB and RWB). Contrary to the hypotheses that DC (positive DC and negative DC) would moderate the associations between both types of stress and both types of well-being, only one significant interaction was found between CI-related stress and negative DC on IWB. Implications of these findings are discussed.
ContributorsJohnson, Courtney K (Author) / Randall, Ashley K. (Thesis advisor) / Robinson-Kurpius, Sharon (Committee member) / Kinnier, Richard (Committee member) / Arizona State University (Publisher)
Created2016