A. Konczykowska

Temperature dependence of DC currents in HBT

A DC thermal-electrical heterojunction bipolar transistor (HBT) model is presented. Only three parameters were needed to simulate completely an HBT with the self-heating effect. It can be very easily implemented in any CAD software which uses the SPICE bipolar junction transistor model. Parameter extraction has been carried out on measured data and good fits were obtained over a wide temperature range. This model can be used to design high-power heterojunction bipolar transistors and circuits with analysis of their thermal effects.<<ETX>>

Symbolic simulation for efficient repetitive analysis and artificial intelligence techniques in CAD

An overview is presented of the symbolic approach for circuit simulation, and its two main application areas are described: (1) fast repetitive analysis, such as is needed for statistical analysis, and optimization, and (2) circuit design assisted by artificial intelligence and related techniques, such as is needed for new circuit architecture investigation. Two dedicated fully symbolic simulators for implementing this symbolic approach are described: SCYMBAL, a simulator for switched-capacitor circuits (SCNs) and the first published of its kind, and SYBILIN, a simulator for analog microwave circuits. To illustrate the capabilities offered to designers by these symbolic simulators, practical design tasks, carried out with the help of SCYMBAL and SYBILIN in the domains of computer intensive repetitive analysis and automated architecture generation and optimization, are presented.<<ETX>>

An approach to integrated numerical and symbolic circuit analysis

An interface to symbolic circuit analysis has been developed for a SPICE-like circuit simulator in order to integrate numerical simulation with an existing program for symbolic circuit analysis. In effect, both numerical and symbolic analyses use the same internal representation of circuits which makes the two approaches truly complementary. This integrated simulation capability is used in simulation-based parameter extraction where all AC small-signal parameters are fitted through the symbolic analysis rather than numerical one, significantly reducing the execution time of the extraction process.<<ETX>>

Distributed transmission lines and time-domain analysis in SPICE-like circuit simulators

Several problems arising in the SPICE implementation of the time-domain analysis of circuits with distributed transmission lines are indicated. It is shown that some simple modifications of the original handling of transmission lines can significantly reduce both the memory requirements and the CPU time needed for this analysis. The modifications make it possible to trade simulation time for accuracy of results. In effect, results more accurate than the original SPICE ones can be obtained with much less computational effort. An example of a microwave oscillator is used as an illustration of the proposed improvements.<<ETX>>

An exhaustive generation of switched-capacitor circuits: a symbolic simulation and artificial intelligence approach

The authors propose a mixed algorithmic-declarative method to solve a problem of structure generation. They demonstrate the usefulness of the declarative language PROLOG in comparison with classical procedural languages and show the importance of symbolic network simulators in this context. This method has been applied to practical problems in the domain of switched-capacitor circuits. SCYMBAL, a symbolic simulator for switched-capacitor circuits, has been used for that purpose. Results obtained in the case of the systematic generation of new integrator structures for high-frequency use are presented. The proposed method can be extended to different classes of analog circuits, for example, RC-filters, microwave circuits, and A/D converters.<<ETX>>

Symbolic simulation: a new approach to automated electronic circuit design

Presents a methodology for the generation of circuit structures using artificial intelligence concepts and symbolic simulation tools. A mixed declarative-algorithmic approach is used for circuit-architecture selection. The usefulness of the declarative languages Prolog, in comparison with classical procedural languages, is pointed out for such an approach. A practical example is given in the domain of mixed analog-digital silicon or gallium arsenide integrated circuits, concerning the generation of integrator building blocks for high frequency applications. This study was executed with SCYMBAL, the symbolic simulator for switched-capacitor networks.<<ETX>>

Symbolic Circuit Analysis

The sections in this article are 1 Basic Concepts 2 History of Symbolic Methods 3 Direct Symbolic Methods 4 Decomposition snd Hierarchical Analysis 5 Approximation Techniques 6 Different Types of Symbolic Analysis 7 Applications of Symbolic Analysis

Function evaluation in symbolic analysis

Different types of applications of symbolic analysis in circuit design are considered regarding the most adequate form of symbolic results storage and manipulation. Different mathematical procedures are examined as a function of their efficiency. Polynomial and non-polynomial admittances are considered. Hierarchical and direct approaches are compared.

Applications of symbolic methods to circuit design: an overview

This paper presents an overview of the popular applications of symbolic methods nowadays as they pertain to circuit design. The specific applications that are discussed are: insight into circuit behavior, device modeling and extraction, behavioral and functional modeling and structural synthesis. The application of symbolic analysis in each of these areas is illustrated via a description of a specific methodology.

Improving performance of parameter extractors through symbolic simulation

In parameter extraction programs, the performance of repeated analyses of linear (or linearized) circuits can be significantly improved by representing the dependence of circuit responses on some parameters in a symbolic form. This symbolic form can then be evaluated very efficiently for different sets of parameter values. An intergrated numerical-symbolic parameter extraction program, called FIT-S, has been developed in which all linear circuit analyses can be performed using a symbolic or numerical approach. A comparisons of execution times is presented for extraction of a submicron HEMTs parameters.