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本文介绍了一种符号模拟程序——ISAAC(模拟集成电路的交互式符号分析法)。该程序以符号表示电路参数,可得到任何模拟集成电路(固定电容和开关电容,CMOS、JFET和双极电路)的所有交流特性。它对传输函数、CMPR、PSRR、阻抗、噪声等参数提供了解析表达式。该模拟程序具有两个新颖的特点:第一,能用基于参数量值的试探性判据来简化表达式,这样可得到仅含主要项的易理解的表达式。第二,失配项的显表达式容许对二次效应,比如PSRR,的精确计算。 符号模拟程序ISAAC与数字模拟程序相比较,能为模拟设计者提供直观的电路特性,而且还是教学的有效工具或模拟设计者的辅助工具。此外,该模拟程序产生完整的电路交流分析模型,可用来对非固定拓扑结构模拟模数生成器进行自校正。该程序的功能以下面几个例子说明。程序的效率由一种专用稀疏距阵算法确定。
This article describes a symbolic simulation program - ISAAC (Analog IC Interactive Symbol Analysis). This program symbolizes the circuit parameters and provides all the ac characteristics of any analog integrated circuit (fixed and switched capacitors, CMOS, JFET and bipolar circuits). It provides analytic expressions for parameters such as transfer function, CMPR, PSRR, impedance and noise. The simulation program has two novel features: first, the expression can be simplified with heuristic criteria based on the magnitude of the parameter, so that an easy-to-understand expression containing only the major terms is obtained. Second, the explicit expression of mismatch terms allows for accurate calculations of secondary effects, such as PSRR. Symbolic Simulator ISAAC offers intuitive circuit features to analog designers as compared to digital simulators, and is an effective tool for teaching or as an aid to analog designers. In addition, the simulator generates a complete circuit analysis model that can be used to self-calibrate non-fixed topology analog modulus generators. The function of this program is illustrated by the following examples. The efficiency of the program is determined by a special thinning matrix algorithm.