University of Macau / Faculty of Science and Technology / Department of Electrical and Computer Engineering

University of Macau / Faculty of Science and Technology / Department of Electrical and Computer Engineering

The continued speed improvement of serial links and appearance of new communication technologies, such as ultra wideband (UWB), have introduced increasing demands on the speed and power specifications of high speed low to medium resolution analog to digital converters (ADCs). While multi channel ADCs can achieve high speeds, they often require extensive and costly post fabrication calibration. A single channel 4 bit flash ADC, suitable for abovementioned or similar applications, implemented entirely using current mode logic (CML) blocks, is presented. CML implementation allows for high sampling rates, while typically providing low power consumption at high speeds. To improve the conversion rate, both the analog (comparator array) and the digital (encoder) parts of the ADC are fully pipelined. Furthermore, the logic functions in the encoder are reformulated to reduce wire crossings and delay and to equalize the wires lengths in the layout. To keep the design simple, inductors are avoided. As a result, a compact design with small wire parasitics is achieved. Moreover, some geometric layout techniques, including a common centroid layout for the resistor ladder, are introduced to reduce the effect of mismatches to eliminate the use of digital calibration. The ADC is designed and fabricated in 0.18um CMOS and operates at 4GS/s. It achieves an effective number of bits (ENOB) of 3.71 (3.14, 2.75) for a 10MHz (0.501GHz, 1.491GHz) signal sampled at 4GS/s (3GS/s, 3GS/s). Differential/integral nonlinearity (DNL/INL) errors are between +/-0.35LSB and +/-0.26LSB, respectively. The ADC consumes 43mW from a 1.8V supply and occupies 0.06mm2 active area. Due to the use of CML circuits, the ADC achieves the highest speed reported for a single channel 4 bit ADC in a 0.18um CMOS technology. It also reports the best power performance among the 4-bit ADCs with similar or higher speeds. The active area is also among the smallest reported. In addition, in this thesis, the signal to noise ratio (SNR) of an ADC is formulated in terms of its INL performance. The related formulas in the literature are not accurate for low resolution ADCs, and yet they do not take the input waveform into account. Two standard waveforms, ramp and sinusoid, are considered here. The SNR formulas are derived and confirmed by simulation results. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

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Indiana University-Purdue University Indianapolis (IUPUI) / Insulin is a hormone that plays a central role in the regulation of human metabolism, and as a drug, is used in the treatment of diabetes mellitus. Hyperglycemia characterizes this condition due to a range of reasons from impaired insulin production by pancreatic beta cells to abnormalities resulting in resistance to insulin action. Depending on time and mechanism of action, the main types of insulin analogs are basal and prandial. Basal insulin analogs are slow-acting insulins that maintain a continuous basal level of insulin in the bloodstream. Prandial insulin analogs are fast-acting and their therapeutic goal is to avoid immediate and late post-prandial hyperglycemia. Most analogs face the problem of chemical degradation and amyloid-like fibril formation (fibrillation) in delivery devices. Thus, many modifications have been made to insulin in the effort to make it more stable and faster-acting. This thesis aims to study the effects of modifications that could be used to design an insulin analog with improved chemical and physical properties, while maintaining biological activity. We studied six amino-acid substitutions to native human insulin in different combinations: desB1 , AB2 , EB3, EA8 , EA14, and EB29. Analogs of the protein were chemically synthesized. Then, fibrillation and circular dichroism assays were performed using purified proteins. The results suggested that EB3 and EA14 are stabilizing modifications that prevent fibril formation, whereas EA8 and EA14 increase the structural stability of an analog. Our findings also suggested that certain modifications in isolation may not impact overall stability, but when combined with others, may show detectable effects, which is why EA8 and EA14 became the focus of further experiments. Cell-based activity assays indicated that all the analogs had similar biological activities. Future work will assess chemical degradation, solubility, amide proton exchange (as monitored by NMR), and mitogenicity.

Jag har valt undersöka det analoga inspelningsformatet rullband, och avtrycket det kommit att sätta för dagens arbetssätt för musikproducenter och musiker. Under arbetet har jag kommit att rent praktiskt fått nyttja inspelningstekniker tidigare standardiserade för en inspelningsstudio, oberoende utav digitala inspelningsverktyg. Därigenom har jag upptäckt mitt intresse för hur komplext och intuitivt just rullband kan vara som inspelningsformat, samt hur arbetssättet påverkar både musikernas prestationer och teknikerns tillvägagångssätt avsevärt. Genom intervjuer med verksamma musikproducenter och studiotekniker, ges en inblick i hur rullbandet används i en modern inspelningsstudio, hur arbetssättet går till samt hur inställningen och uppfattningen om rullband kommit att förändras med tiden. Intervjuerna bidrar som underlag för en konstnärlig process, där jag genom en egen produktion inspelad på rullband ger en inblick i på vilka sätt rullbandet har påverkat inspelningstekniken till vad det är idag.

Demand for capable and reliable semiconductor and fabrication technology for high temperature and power electronics applications has been increasing in recent years. Silicon Carbide (SiC), as a wide bandgap compound semiconductor, demonstrates superior characteristics such as high thermal conductivity, high breakdown voltage, and long-lasting reliable operation at elevated temperature. SiC-based circuits and systems are capable to offer significant performance enhancements to various applications. Integrated power management units and conversion modules in HEVs, integrated sensors for aircraft engines, development of small-sized portable power generators are among many applications that require reliable circuits with long-lasting functional lifetime. Nevertheless, there are numerous challenges associated with the design and fabrication of SiC-based circuits. The aim of this research is to practically design and implement novel operational amplifiers (opamps) based on Vertical Channel 4H-SiC JFET (SiC JFET) that can be utilized as sub-circuits of integrated SiC JFET-based circuits and systems. Recently, SiC power JFET-based power management units were developed that deploy non-SiC JFET-based circuits for analog signal processing, driving, and control, because all SiC JFET-based circuits were not available for full integration. However, utilizing SiC JFET for analog design (in order to close the mentioned gap) exhibits significant design challenges, even at room temperature. These fundamental challenges are low intrinsic gain, the requirement to limit the gate to source voltage range, and restrictions on utilizing channel length as a design parameter due to fabrication complexity. These challenges must be successfully overcome at room temperature, before moving towards high temperature SiC JFET-based analog design. The main objective of this dissertation is to establish a design base, overcome the challenges, demonstrate the feasibility, and present all SiC JFET-based opamps that are designed for gain, CMRR, and overall performance. Before attempting to design, both Enhancement and Depletion Mode SiC JFETs are characterized, analyzed, and modeled for simulation. Unique and reliable opamp configurations are presented that take design requirements into account, use threshold voltage instead of channel length as a design parameter, and employ gain enhancement techniques while obtaining maximum possible bandwidth. The final opamps are fabricated and tested and the results show that the objective is accomplished.

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