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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
ABSTRACT Research suggests that there are benefits of early intervention and in focusing on mental health for infants and toddlers who have been maltreated. Court Teams for Infants and Toddlers is a model program designed to improve developmental outcomes using a systemic change approach. Multi-system collaboration between the courts, child welfare, health professionals, child advocates, and community partners are promoted to increase awareness and improve outcomes for infants and toddlers who have been removed from their parents. The Court Teams model in Arizona is known as Best for Babies. This study looks at implementation efforts of Best for Babies in two counties, Yavapai and Pima, and the unique perspectives of foster parents and attorneys representing the infants and toddlers while in the foster care system. It is important for purposes of effective program implementation to understand whether the Best for Babies program has impacted how these stakeholders address the unique needs of infants and toddlers. Findings reveal that most foster parents in this study were not familiar with the Best for Babies program; however, many of the comments shared are aligned with the values of the program. For example, all participants commented that collaboration among various stakeholders is necessary. Areas of opportunity were also illustrated in the findings regarding Best for Babies program implementation. For instance, the study found that even those foster parents familiar with the program could not attribute an impact on their care of infants and toddlers specifically to Best for Babies.
ContributorsWhite, Jennifer (Author) / Krysik, Judy (Thesis advisor) / Roe-Sepowitz, Dominique (Committee member) / Ayón, Cecilia (Committee member) / Arizona State University (Publisher)
Created2011
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
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
Description
The Arizona state child welfare system has recently experienced an increase in the number of children and youth living in out-of-home care. A lack of licensed foster homes has resulted in many of these children residing in congregate care. This study sought to determine what role, if any, personal and policy bias against five demographic groups (i.e., ethnicity, sexual orientation, marital status for individuals and couples, and educational level) plays in this insufficiency of foster homes. In this pilot study a group of foster and adoption licensing agency executives and directors (n=5) were surveyed and qualitatively interviewed with the aim of discerning if bias is present at the personal and agency policy levels and to seek input for a future study with direct-service staff. Results indicate a discrepancy between personal and policy bias within agencies. Additionally, evidence suggests a policy bias which results in unmarried couples and single parents being perceived as inferior placement options. Implications for future research are discussed.
ContributorsPearson, Patience Hope (Author) / Ferguson-Colvin, Kristin (Thesis advisor) / Mendoza, Natasha (Committee member) / Krysik, Judy (Committee member) / Arizona State University (Publisher)
Created2017
Description
Peer-parenting in child welfare is a developing field with a growing repository of research that demonstrates a positive effect on child welfare case outcomes such as rates of reunification and parent engagement. Peer-parenting also benefits the peer-parents, who apply their lived child welfare experience to their service to clients, by providing fulfilling and satisfying work opportunities. However, there is a lack of research focusing on workforce characteristics or workforce development for peer-parents. Qualitative interviews were conducted with professional peer-parents in the child welfare field to understand their perceptions and experiences being employed as a peer-parent. The findings demonstrate a deep commitment to their work as peer-parents, the important role that leadership and supervision plays, and valuable insight into what improvements can be made to the workforce.
ContributorsHamilton, Samantha (Author) / Krysik, Judy (Thesis advisor) / Ferguson, Kristin (Committee member) / Wu, Qi (Committee member) / Arizona State University (Publisher)
Created2023
Description
Much of the current literature regarding the well being of children of incarcerated
parents has focused largely on the trauma that results from losing a parent to incarceration. Little research has been dedicated to examining the pre-existing trauma and negative life experiences these children are exposed to prior to parental incarceration. Using cross-sectional data on children (N = 1,221) from a representative study of Arizona Department of Corrections inmates, the present study examines the relationships among children who have contact with Child Protective Services (CPS) prior to parental incarceration and: (1) parental substance abuse, (2) exposure to violence and (3) parental mental illness. Nearly a quarter of all children whose inmate parents were interviewed were contacted by CPS before experiencing parental incarceration. Children whose inmate parents reported being unemployed or less involved in the lives of their children and children who were reportedly exposed to violence were significantly more likely to have been contacted by CPS prior to experiencing parental incarceration as were younger children. The children of incarcerated mothers were more likely to have been contacted by CPS than were the children of incarcerated fathers. This effect remained even after controlling for additional parent, child and family risk factors for CPS contact such as prior history of incarceration and race.
parents has focused largely on the trauma that results from losing a parent to incarceration. Little research has been dedicated to examining the pre-existing trauma and negative life experiences these children are exposed to prior to parental incarceration. Using cross-sectional data on children (N = 1,221) from a representative study of Arizona Department of Corrections inmates, the present study examines the relationships among children who have contact with Child Protective Services (CPS) prior to parental incarceration and: (1) parental substance abuse, (2) exposure to violence and (3) parental mental illness. Nearly a quarter of all children whose inmate parents were interviewed were contacted by CPS before experiencing parental incarceration. Children whose inmate parents reported being unemployed or less involved in the lives of their children and children who were reportedly exposed to violence were significantly more likely to have been contacted by CPS prior to experiencing parental incarceration as were younger children. The children of incarcerated mothers were more likely to have been contacted by CPS than were the children of incarcerated fathers. This effect remained even after controlling for additional parent, child and family risk factors for CPS contact such as prior history of incarceration and race.
ContributorsMcCaskill, Whitney (Author) / Rodriguez, Nancy (Thesis advisor) / Wright, Kevin (Committee member) / Tasca, Melinda (Committee member) / Krysik, Judy (Committee member) / Arizona State University (Publisher)
Created2014