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Showing papers in "IEEE Transactions on Circuits and Systems in 2000"


Journal Article
TL;DR: In this article, a four-quadrant CMOS current-mode multiplier based on the square-law characteristics of an MOS transistor operated in the saturation region is presented, where the output current is independent of device parameters.
Abstract: In this work, we present a four-quadrant CMOS current-mode multiplier based on the square-law characteristics of an MOS transistor operated in the saturation region. One advantage of this multiplier is that the output current is independent of MOS transistor device parameters; another, that the input resistance is independent of the input current. Simulations of the multiplier demonstrate a linearity error of 1.22%, a THD of 1.54%, a -3 dB bandwidth of 22.4 MHz, and a maximum power consumption of 0.93 mW. Operation of the multiplier was also confirmed through an experiment using CMOS 4007 IC's.

97 citations


Journal Article
TL;DR: An extension of the invariance principle, which includes cases where the derivative of the Lyapunov function along the solutions is positive on a bounded set, is given and is used to obtain estimates of attractors which are independent of coupling parameters.
Abstract: In many engineering and physics problems it is very hard to find a Lyapunov function satisfying the classical version of the LaSalle's invariance principle. In this work, an extension of the invariance principle, which includes cases where the derivative of the Lyapunov function along the solutions is positive on a bounded set, is given. As a consequence, a larger class of problems may now be considered. The results are used to obtain estimates of attractors which are independent of coupling parameters. They are also applied to study the synchronization of coupled systems, such as coupled power systems and coupled Lorenz systems. Estimates on the coupling term are obtained in order to accomplish the synchronization.

70 citations


Journal Article
TL;DR: In this paper, the Colpitts oscillator is taken as a case study and the occurrence of discontinuous bifurcations, namely, border-collision bifurbations, in a piecewise-linear model of the oscillator was discussed.
Abstract: This paper deals with the implications of considering a first-order approximation of the circuit nonlinearities in circuit simulation and design. The Colpitts oscillator is taken as a case study and the occurrence of discontinuous bifurcations, namely, border-collision bifurcations, in a piecewise-linear model of the oscillator is discussed. In particular, we explain the mechanism responsible for the dramatic changes of dynamical behavior exhibited by this model when one or more of the circuit parameters are varied. Moreover, it is shown how an approximate one-dimensional (1-D) map for the Colpitts oscillator can be exploited for predicting border-collision bifurcations. It turns out that at a border collision bifurcation, a 1-D return map of the Colpitts oscillator exhibits a square-root-like singularity. Finally, through the 1-D map, a two-parameter bifurcation analysis is carried out and the relationships are pointed out between border-collision bifurcations and the conventional bifurcations occurring in smooth systems.

43 citations


Journal Article
TL;DR: In this paper, the color palette design methods for compressed images and videos are presented, which use the reduced, rather than the whole, image for the colour palette design to avoid the heavy computation in image or video decompression.
Abstract: Many display devices nowadays still allow a limited number of colors, called color palette, to be displayed simultaneously. Besides, images and videos in most World Wide Web databases are in compressed formats. Therefore, it becomes an important issue to retrieve a suitable color palette from compressed domain in order to have fast and faithful color reproduction for these devices. In this paper, the color palette design methods for compressed images and videos are presented. The proposed approaches use the reduced, rather than the whole, image for the color palette design to avoid the heavy computation in image or video decompression. Also, for compressed videos, a shifting-window scheme is proposed to smooth out color variations in the change of color palette. In these methods, we extend the dependent scalar quantization algorithm of a single image to accomplish the color palette design. Experimental results show that the output image quality of the proposed methods is acceptable to human eyes. In addition, empirical results show that the proposed shifting-window scheme can reduce the main problem of displaying quantized image sequences, screen flicker.

1 citations