Thesis (M. Phil.)--University of Hong Kong, 2007. / Title proper from title frame. Also available in printed format.

The parasitic components of MOS switches at high speeds affect the linearity and resolution of CMOS sample and hold circuits. CCD-based circuit design can offer good performance at high speeds. This thesis presents the design of sample and hold circuits using charge-coupled device structures in a standard CMOS process. Three sample and hold circuits have been built and tested for linearity and speed performance. The CCD S/Hs have been characterized using a continuous-time integrator and a Δ∑ ADC. The CCDs, with a switched capacitor amplifier at the output, achieve an SFDR of 54dB for an input signal V[subscript in]=2.6V+0.4Vpp at f[subscript in]=10.1KHz. / Graduation date: 2003

The molecular weight distributions of two high molecular weight (M[subscript w]>>1 million) polyethylene polymers, WSR-308 and WSR-301, were characterized with gel permeation chromatography (GPC) coupled with a multi-angle laser light scattering detector (MALLS). The M[subscript w] of the WSR-308 was found to be 5.10x10⁶ g/mol with a molecular weight range from about 1 million g/mol to as high as 10 million g/mol. The M[subscript w] of the WSR-301 was found to be 3.16x10⁶ g/mol with the lowest molecular weight about 400,000 g/mol while the highest molecular weight component may have been as high as 8 million g/mol. Attempts to measure the M[subscript w] of the two polymers using static light scattering (SLS) techniques proved to be difficult. In conjunction with these studies, drag reduction and shear degradation studies of the two polymers in water were also conducted. Solutions of the two polymers, ranging from 1 to 10 ppm including mixtures of the two, were tested in a pipe-flow apparatus to obtain friction factor and %DR data. In every case, the greater the concentration and/or the molecular weight of the polymer, the greater the drag reduction effects. Additionally, the higher molecular weight polymer and mixtures with a greater weight percentage of the higher molecular weight polymer were found to shear degrade less quickly than otherwise. A unique point along the maximum drag reduction asymptote (MDA) termed the "divergence point" was a focus of this study and an energy model based on frictional losses correlates well to the data. The correlation developed here relates the difference in frictional losses between the solvent by itself and the polymer solution directly to the mass concentration and molecular weight of the polymer. This frictional difference was proportional to the product of the mass concentration and molecular weight where both quantities were to approximately the first power. / Graduation date: 2002

The dependence of the substrate resistance, R[subscript sub], for MOS transistor RF modeling on transistor biasing and layout is studied from device simulations and measurements. Though R[subscript sub] is found to be bias dependent, the error incurred by assuming a constant value equal to the DC resistance is not significant. A scalable model for R[subscript sub] of multiple gate fingers is developed. This model is simple to extract and gives good agreement for the output admittance of a MOSFET. The model is validated by measurements on DC test structures fabricated in a TSMC 0.35 ��m CMOS process. The dependence of Rb on transistor dimensions and the location of substrate contacts with respect to device active area is also presented. A low noise amplifier (LNA) is designed and fabricated in the 0.35 ��m TSMC process to show the effect of R[subscript sub] on the performance of a LNA. / Graduation date: 2003

This thesis presents an automated methodology to calibrate the substrate profile for accurate prediction of substrate parasitics using Green's function based extractors. The technique requires fabrication of only a few test structures and results in an accurate three layered approximation of a heavily doped epitaxial silicon substrate. The obtained substrate resistances are accurate to about 10% of measurements. Advantages and limitations of several common measurement techniques used to measure substrate z-parameters and resistances are discussed. A new and accurate z-parameter based macro-model has been developed that can be used up to a few GHz for P��� for contacts that are as close as 2��m. This enhanced model also addresses the limitations of previous models with regards to implementation aspects and ease of integration in a CAD framework. Limitations of this modeling approach have been investigated. The calibration methodology can be used along with the scalable macromodel for a qualitative pre-design and pre-layout estimation of the digital switching noise that couples though the substrate to sensitive analog/RF circuits. / Graduation date: 2004

Graduation date: 2000

Advancements in the sophistication and complexity of modern electronic systems are creating a need for highly integrated systems with ever higher operational frequencies. The economical demands of these systems dictate that they be implemented using low cost fabrication technologies, such as digital CMOS. One of the major challenges facing circuit designers is the difficulty in implementing high frequency RF analog circuits on these types of technologies. Analog circuits which make use of parasitic-laden components such as inductors are especially difficult to realize. The purpose of this thesis is to investigate the design and application of an optimization tool based on simulated annealing to this type of problem. The goal is to have the optimizer incorporate these unavoidable component parasitics into a design, and thus eliminate any undesirable performance degradation. The optimization technique will be applied to the design of a CMOS RF distributed amplifier. This type of amplifier has a flat gain characteristic over an exceptionally wide bandwidth, and it is heavily reliant on inductive structures. Historically, an amplifier of this type has never been implemented on a standard CMOS process, without the use of bondwire inductances or special processing techniques. However, it will be shown in this thesis that, with the aid of the optimization technique, a distributed amplifier design can be successfully realized on a standard CMOS process. / Graduation date: 1999

Currently, the two most critical factors of microprocessor design are performance and power. The optimum balance of these two factors is reflected in the speed-power product(SPP). 32-bit CMOS adders are used as representative circuits to investigate a method of reducing the SPP. The purpose of this thesis is to show that sizing gates according to fan-out and removing buffer drivers can reduce the SPP. This thesis presents a method for sizing gates in large fan-out parallel prefix circuits to reduce the SPP and compares it to other methods. Three different parallel prefix adders are used to compare propagation delay and SPP. The first adder uses the depth-optimal prefix circuit. The second adder is based on Wei, Thompson, and Chen's time-optimal adder. The third adder uses a recursive doubling formation where all cells have minimum transistor width dimensions. The component cells in the adders are static CMOS as described by Brent and Kung. For all circuits, the smallest propagation delay occurs when the highest voltage supply is applied. The smallest SPP occurs when the lowest voltage supply is applied, but with the lowest performance. The Recursive Doubling Adder always has the lowest propagation delay for a particular set of parameters. However, its SPP is nearly equal to the Brent-Kung Adders and lower than Wei's Adder. The power-frequency analysis reveals that a decrease in Vt causes higher power consumption due to leakage. / Graduation date: 1999

In this thesis, novel design techniques have been proposed for implementing high-linearity SC circuits in a standard digital CMOS process. They use nonlinear MOSFET capacitors instead of linear double-poly capacitors. To reduce their nonlinearities, a bias voltage is applied to keep MOSFET capacitors in their accumulation regions. For further reduction of distortion, two capacitors can be connected in series or in parallel so that a first-order cancellation of the nonlinearity can be achieved. Experimental results demonstrated that the among these techniques series compensation is the most effective for reducing the nonlinearity of MOSFET capacitors. A novel predictive SC amplifier has been proposed for its insensitivity to op-amp imperfections. Experimental results show that the S/THD of the predictive SC amplifier was 10 dB larger than that of the non-predictive one. It was also shown that a predictive circuit was effective for reducing the nonlinearity caused by the op-amp and/or the MOSFET capacitors. It has been demonstrated that a two-stage op-amp with a large output swing can be fabricated in a standard digital CMOS process. The frequency compensation was accomplished using a source follower and a MOSFET capacitor. An SC amplifier using this two-stage op-amp and double-poly capacitors was fabricated, and it exhibited a large linear output range. A MOSFET-only digitally controlled gain/loss circuit was designed and fabricated in a 1.2�� CMOS process. It demonstrated that the series compensation is effective not only for a large output swing in an amplifier, but also for a large input swing in an attenuator. A pipeline D/A converter utilizing MOSFET capacitors was designed as another application of charge processing technique. It consisted of three parts: a V-Q conversion stage, a charge transfer stage, and a Q-V converter. A new switch configuration which enables the series compensation to have a large bias voltage has also been proposed. It was shown that it works well, and it will be helpful for low-voltage operation, too. / Graduation date: 1998

Substrate switching noise is becoming a concern as integrated circuits get larger and speeds get faster. Mixed-mode integrated circuits are especially affected as the substrate noise interferes with sensitive analog circuits resulting in limited signal to noise ratios. This thesis serves to study the cause of the noise at the point where it is generated to the way it propagates to the analog circuits, and presents several approaches to reduce the switching noise. In addition, it examines the substrate impedance as being a key element to successful and reliable design for low-noise CMOS mixed-signal integrated circuits. Utilizing the substrate lead inductance and current-variable capacitances through the use of guard ring diodes, resonant frequencies which provide a low impedance path to ground are created. These can be tuned to coincide with problematic noise frequency components or to cancel the pin and package resonance, thus suppressing noise and improving reliability. / Graduation date: 1997