Circuit Simulation Program SPICE Research Articles

A physical parametric transistor model for CMOS circuit simulation

A transistor model for use in simulation of analog and digital CMOS circuits is described. This model treats inversion devices and normally off accumulation devices individually. The analysis, based on surface potential, is carried out in voltage space. Single expressions for drain current and terminal charges are obtained that conserve charge and give accurate DC, AC, and transient solutions. Derivatives of current and charges are continuous, thus removing a major source of nonconvergence in circuit simulation. The model precalculates and stores charge densities, requiring significantly less computer memory than table look up methods while still describing devices with arbitrary channel width-to-length ratios. The need for measuring device capacitance is eliminated because terminal charge and capacitance are computed from the same parameters that are used to compute drain current. Because the parameters are physical, the model can be used to monitor and predict the effect of process changes. The model has been implemented in the SPICE circuit simulation program and a variety of typical devices and circuits have been simulated successfully. CPU time requirements are comparable to the existing SPICE model. >

SPICE implementation of lossy transmission line and Schottky diode models

The author describes models for the lossy transmission line and the Schottky diode that are incorporated into the source code of the circuit simulation program SPICE (version 2G.6). The model used for the lossy transmission line was derived by A.J. Gruodis (1979). The DC model for the Schottky barrier diode as shown was formulated by D.B. Estreich (1983). Examples used to verify the models are given.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A method to predict harmonic distortion in small-geometry MOS analog integrated circuits

A method to predict the small-signal linear gain and level of harmonic distortion in analog MOS circuits is presented. This method, based on a generalized nonlinear transfer function approach, lends itself to implementation in the AC small-signal analysis routine of the circuit simulation program SPICE. A low-frequency nonlinear distortion model based on the CSIM simulator MOSFET model is applied to three simple MOSFET circuits. Results presented emphasize the need to consider small-signal quantities in the development of MOSFET models and in the determination of device parameters. The method can be easily extended to include capacitive effects and a prediction of intermodulation distortion.

A Spice Model for Enhancement-and Depletion-Mode GaAs FET's

An improved model for the GaAs MESFET has been implemented in the source code of the circuit-simulation program SPICE. New features include 1) an accurate model for the Schottky barrier, which allows simulation of both enhancement- and depletion-mode devices; 2) detailed modeling of the nonlinear gate-source and gate-drain capacitance; and 3) a user-specifiable value for the exponent in the expression for the dependence of the dc drain current upon the gate-source voltage. Also discussed are some important points concerning the charge-voltage equations that must accompany the new model's capacitance-voltage equations within SPICE. The new GaAs FET SPICE model is believed to be the most comprehensive one available to date in the public domain.

A SPICE Interactive Graphics Preprocessor

This paper discusses the development and use of an interactive computer graphics interface to the SPICE circuit simulation program. This package provides for the convenient input of the circuit topology and the values of the circuit elements from the designer, and creates a structured database to store the circuit information.

A large-signal GaAs MESFET model implemented on SPICE

A device model that predicts large-signal GaAs MESFET performance has been implemented on the large-scale circuit simulation program SPICE. The model takes into consideration drift velocity saturation, channel length modulation, and subthreshold current effects. In addition, the model depends primarily on physical (i.e. material and geometric) rather than empirical parameters. Combined with the SPICE program, a general CAD tool is formed which can be used to aid in the design of GaAs circuits such a power amplifiers, oscillators, mixers, and fast-switching digital integrated circuits. Model predictions are compared to measured device performance, and limitations of this large-signal circuit design approach are discussed.

A Physical and SPICE-Compatible Model for the MOS Depletion Device

An MOS depletion device model that is compatible with SPICE circuit simulation program and based on device physics is described. The depletion device is modeled by an equivalent circuit consisting of various well-characterized semiconductor devices, for example, the enhancement MOS device and the JFET. IT has the advantages of both the existing physical and empirical models. The model is applicable to immediate circuit simulation and device fabrication. Derivation of the model along with its parameters for the Gaussian impurity distribution is given. Implementation of circuit simulation with SPICE is demonstrated. More accurate results compared to the empirical model are obtained.

A Complete GaAs MESFET Computer Model for SPICE (Short Papers)

A model for the gallium arsenide MESFET has been implemented into the source code of the well-known circuit simulation program SPICE. Both large-signal and small-signal simulations of MESFET circuits are now possible within the familiar framework and data format of SPICE. The line-by-line modifications made to SPICE to achieve the model implementation will be made available to interested researchers.

Chopper circuit put on op-amp chip : L. Altman. Electronics August 16 (1973). p. 125

To facilitate gas sensor design with the associated signal-conditioning circuitry, a previously developed gas adsorption model is implemented in the popular circuit simulation program SPICE. The model is based on the gas adsorption theory. With the adsorption model implemented in SPICE, the performance of a MOSFET gas sensor integrated with the associated circuitry can be studied. The analysis was applied to three sensors, namely, the H2 sensor, the NH3 sensor and the CO sensor. A noise analysis of the sensors was also performed and their lower bounds of detectivity determined. A chopper-stabilized circuit was applied to the sensing circuitry. Simulation results show that noise in gas sensors can be reduced.