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In chopper amplifiers, the interaction between the input signal and the chopper clock can give rise to intermodulation distortion (IMD). This chopper-induced IMD is mainly due to amplifier delay, which causes large pulses at the output of the amplifier's output chopper. This article proposes the use of a so-called fill-in technique to eliminate these pulses, and thus the resulting IMD, by multiplexing the outputs of two identical amplifiers that are chopped in quadrature. A prototype chopper-stabilized amplifier was implemented in a 180-nm CMOS process. Measurements show that the fill-in technique suppresses chopper-induced IMD by 28 dB, resulting in an IMD of -126 dB for input frequencies near 4 FCH (=80 kHz). It also improves the amplifier's two-tone IMD (with 79 and 80 kHz inputs) from -97 to -107 dB, which is the same as that obtained without chopping., Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public., Electronic Instrumentation, Microelectronics

In chopper amplifiers, the interaction between the input signal and the chopper clock can give rise to intermodulation distortion (IMD). This chopper-induced IMD is mainly due to amplifier delay, which causes large pulses at the output of the amplifier's output chopper. This article proposes the use of a so-called fill-in technique to eliminate these pulses, and thus the resulting IMD, by multiplexing the outputs of two identical amplifiers that are chopped in quadrature. A prototype chopper-stabilized amplifier was implemented in a 180-nm CMOS process. Measurements show that the fill-in technique suppresses chopper-induced IMD by 28 dB, resulting in an IMD of -126 dB for input frequencies near 4 FCH (=80 kHz). It also improves the amplifier's two-tone IMD (with 79 and 80 kHz inputs) from -97 to -107 dB, which is the same as that obtained without chopping., Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public., Electronic Instrumentation, Microelectronics

Stress relaxation is the phenomenon where stress of materials decreases under constant strain. In several previous studies, it was found that the stress relaxation makes uniform elongation larger, showing a possibility that this phenomenon can be utilized to increase the forming limit in combination with the flexible slide motion of a servo press. However, the stress relaxation phenomenon has not yet been sufficiently clarified. Authors previously investigated the stress relaxation behavior by applying several models where stress relaxation was described as an elasto-viscoplasticity behavior. However, a unified and quantitative description of strain rate sensitivity of flow stress and stress relaxation has not been sufficiently studied. In this study, we investigated the influence of strain, strain rate and relaxation time on stress relaxation phenomena of high strength steel sheets. Strain rate sensitivity of flow stress was modelled with m-power law. Stress relaxation behavior was also successfully approximated by a model derived from the m-power law with the parameters obtained by strain rate sensitivity tests, which suggests that both the strain rate sensitivity and the stress relaxation were based on a unified elasto-viscoplasticity. The mechanisms of stress relaxation was also discussed through numerical analyses.

This thesis describes the theory, design, and implementation of chopper operational amplifiers (op-amps) in CMOS integrated circuits (ICs). The chopping technique periodically corrects DC errors of such op-amps, so that low 1/f noise and stable, microvolt-level offset can be achieved. However, chopping causes switching artifacts at the amplifier’s output, e.g. up-modulated ripple and glitches, which are usually attenuated by low-pass filtering. Therefore, chopper op-amps have mainly been limited to low frequency applications. In this thesis, advanced circuit techniques are proposed to attenuate such switching artifacts without decreasing the usable signal bandwidth, thus enabling the use of chopper op-amps in a broader range of applications. Three chopper op-amps are designed, fabricated, and measured, so that the proposed techniques can be evaluated and compared with those of the other state-of-the-art designs. In the first design, a ripple reduction technique called auto-correction feedback (ACFB) is proposed, which continuously detects and cancels the ripple in a power and area efficient manner, so that the overall op-amp only draws 13µA from a 1.8V to 5.5V supply and occupies a 0.64mm2 die area. In the second design, an adaptive clock boosting technique for input switches is proposed, so that their charge injection mismatch is minimized and independent of changes in the supply and input common-mode voltages. As a result, 0.5µV maximum offset and 5.6nV/√Hz noise PSD are achieved over the op-amp’s entire rail-to-rail input common-mode range. In the third design, six parallel input transconductors are driven by interleaved 800kHz clocks, which pushes the PSD peak up to 4.8MHz. Furthermore, an on-chip charge mismatch compensation circuit is employed to reduce the maximum input bias current from 1.5nA down to 150pA in post-production trimming., Electronic Instrumentation

Important considerations for the process at the Japanese refinery are preventing the growth of coating accretions in the Waelz kiln and improving the rate of zinc volatilisation. Simulation predictions and the results of industrial operation are reported and compared, with the conclusion that a series of analyses and improvements has achieved almost complete control of kiln accretions: shut-down time cause by accretions has decreased by almost 200 h, the Zn evaporation rate has imrpoved by c.3%, unit coke consumption has improved by 150 kg/recovered tonne Zn and refractory life has almost doubled., Important considerations for the process at the Japanese refinery are preventing the growth of coating accretions in the Waelz kiln and improving the rate of zinc volatilisation. Simulation predictions and the results of industrial operation are reported and compared, with the conclusion that a series of analyses and improvements has achieved almost complete control of kiln accretions: shut-down time cause by accretions has decreased by almost 200 h, the Zn evaporation rate has imrpoved by c.3%, unit coke consumption has improved by 150 kg/recovered tonne Zn and refractory life has almost doubled.