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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
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
Learning analytics application is evolving into a student-facing solution. Student-facing learning analytics dashboards (SFLADs), as one popular application, occupies a pivotal position in online learning. However, the application of SFLADs faces challenges due to teacher-centered and researcher-centered approaches. The majority of SFLADs report student learning data to teachers, administrators, and researchers without direct student involvement in the design of SFLADs. The primary design criteria of SFLADs is developing interactive and user-friendly interfaces or sophisticated algorithms that analyze the collected data about students’ learning activities in various online environments. However, if students are not using these tools, then analytics about students are not useful. In response to this challenge, this study focuses on investigating student perceptions regarding the design of SFLADs aimed at providing ownership over learning. The study adopts an approach to design-based research (DBR; Barab, 2014) called the Integrative Learning Design Framework (ILDF; Bannan-Ritland, 2003). The theoretical conjectures and the definition of student ownership are both framed by Self-determination theory (SDT), including four concepts of academic motivation. There are two parts of the design in this study, including prototypes design and intervention design. They are guided by a general theory-based inference which is student ownership will improve student perceptions of learning in an autonomy-supportive SFLAD context. A semi-structured interview is used to gather student perceptions regarding the design of SFLADs aimed at providing ownership over learning.
ContributorsLi, Siyuan (Author) / Zuiker, Steven (Thesis advisor) / Cunningham, James (Committee member) / Lande, Micah (Committee member) / Arizona State University (Publisher)
Created2019
Description
In this study, the current literature regarding student engagement and student voice were reviewed to explore the connection between these two classroom elements. Currently, frequently incorporating student voice in order to increase student engagement most commonly takes place at the high school and university levels. Thus, utilizing Finn’s (1989) participation-identification theory, this study set out to implement a practical design intervention in an elementary classroom to increase student engagement through the incorporation of student voice. Using Design-Based Research, I implemented a collaborative reflection process which allowed students, teacher/researcher, and co-educators to provide feedback on classroom task and participant structures. The feedback was then considered for further iterations of the task and participant structures. This was a pilot study of the collaborative reflection process and was implemented in a fourth-grade math classroom with 26 participants. Along with participating in the collaborative reflection process, the student participants also took a 26 question Learner Empowerment Measure to survey their feelings of identity with the classroom before and after the design intervention. After analyzing audio data gathered during the classroom tasks, as well as student feedback, it was found that student participation did increase due to the design intervention. However, there was no measurable difference in students’ feelings of identity with the classroom due to the collaborative reflection process. Future studies should consider implementing the collaborative reflection process in multiple classrooms across diverse activities during the school year.
ContributorsSanders, Elizabeth (Author) / Zuiker, Steven (Thesis advisor) / Jordan, Michelle (Committee member) / Henderson, J. Bryan (Committee member) / Arizona State University (Publisher)
Created2019
Description
Today’s science education has been highly criticized in the United States despite reform efforts that attempt to promote more wholistic and integrated goals for teaching and learning science, which include both the understanding of key content and the acquisition of scientific skills. Outdoor education may be a means with which to better engage students in science, but educators often find this type of teaching difficult to adopt for a variety of reasons. Nature journaling may be a useful access point to outdoor education for teachers experiencing those barriers. This study examines a six-month implementation of nature journaling activities in a high school Ecology & Animal Behavior course. It was found that students completing nature journaling in this classroom utilized both scientific knowledge and scientific practices in their work, and that instances and depth of these demonstrations increased as a general trend over time, which may be considered successful learning according to situativity theory. Further, students communicated their understanding of what they were accomplishing through their journal work as highly beneficial, though their own perceptions of their competencies in scientific practices did not change. Though additional research needs to be conducted, this study points to a potentially positive relationship between modern science education and outdoor learning through nature journal activities.
ContributorsSuloff, Sarah (Author) / Weinberg, Andrea (Thesis advisor) / Jordan, Michelle (Committee member) / Franz, Nico (Committee member) / Arizona State University (Publisher)
Created2021