General-purpose Circuit Simulator Research Articles

Simulation of action potential propagation in complex terminal arborizations

Action potential propagation in complex terminal arborizations was simulated using SPICE, a general purpose circuit simulation program. The Hodgkin-Huxley equations were used to simulate excitable membrane compartments. Conduction failure was common at branch points and regularly spaced boutons en passant. More complex arborizations had proportionally more inactive synapses than less complex arborizations. At lower temperature the safety factor for impulse propagation increased, reducing the number of silent synapses in a particular arborization. Small structural differences as well as minute changes in the discharge frequency of the action potential resulted in very different activation patterns of the arborization and terminal boutons. The results suggest that the structural diversity of terminal arborizations allows a wide range of presynaptic information processing. The results from this simulation study are discussed in the context of experimental results on the modulation of synaptic transmission.

A physics-based MOSFET noise model for circuit simulators

Discussed is a physics-based MOSFET noise model that can accurately predict the noise characteristics over the linear, saturation, and subthreshold operating regions but which is simple enough to be implemented in any general-purpose circuit simulator. Expressions for the flicker noise power are derived on the basis of a theory that incorporates both the oxide-trap-induced carrier number and correlated surface mobility fluctuation mechanisms. The model is applicable to long-channel, as well as submicron n- and p-channel MOSFETs fabricated by different technologies, and all the model parameters can be easily extracted from routine I-V and noise measurements. >

BITSIM—A General Purpose Circuit Simulator

In this paper we describe a general purpose circuit simulator, BITSIM, based on a new hybrid equation formulation technique. The formulation technique uses graph decomposition and exploits the good structural properties of the topological constraints imposed by KVL and KCL. Given any arbitrary network N and a partition of its branches into sets A and B, we decompose it into two networks NAL and NBK. The simultaneous solution of NAL and NBL under matching boundary conditions is equivalent to the solution of N. We use efficient graph theoretic algorithms (0(|E|); E=set of edges of N) to generate and NBK This needs to be done only once per simulation run. Equation formulation for NAL is of the NODAL ADMITTANCE type while for NBK it is of the LOOP IMPEDANCE type. The resulting system matrix has good computational properties such as NEAR POSITIVE DEFINITENESS. To exploit them BITSIM's linear equation solver is based on an iterative method (GENERALISED CONJUGATE RESIDUAL).

Modeling and simulation of interconnection delays and crosstalks in high-speed integrated circuits

A computer model for n parallel microstrip lines is developed for circuit simulation. This model for the lossy transmission line system can be readily implemented into circuit simulators and can accurately simulate the delay and crosstalk effects of interconnects in high-speed integrated circuits. Modal analysis is applied to decouple the n-coupled-line system into n independent lines, and the characteristic solutions of telegraph equations are represented by a set of simple time-varying equivalent circuits. The model has been implemented in a general-purpose circuit simulator, iSMILE, which is compatible with SPICE. Simulation results on propagation delay times and crosstalk are presented for high-speed GaAs HEMT (high-electron-mobility transistor) integrated circuits.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

SPICE simulation of quasi-resonant zero-current-switching DC-DC convertors

A simple, topology-independent method is proposed for simulating the responses of open and closed-loop quasiresonant DC-DC convertors operating in the zero-current-switching mode (ZCS-QRC). The method hinges on the substitution of the resonant network and switch assembly, fundamental in the realisation of such systems, by an equivalent circuit which represents its average behaviour. This permits simulation by a general-purpose electronic circuit simulator such as SPICE. The proposed approach is demonstrated by presenting the simulation results of a buck-boost convertor.

Analysis of propagation delays in high-speed VLSI circuits using a distributed line model

A scattering parameter-based homogeneous distributed-line model with arbitrary initial and boundary conditions is proposed and its implementation in a general-purpose circuit simulator supporting user functions is described. Using a GaAs 0.5- mu m MESFET technology, the chip delays in very high-speed VLSI circuits are calculated. The performance requirements of transistors for high-density integration and for long-distance interconnection drivers are discussed with respect to properties of lossy and lossless interconnection lines. The evaluation of chip delays shows that sub-100-ps VLSI circuits (gate count beyond 10/sup 5/) should involve: (1) complementary logic gates using transistors with transconductance of 1-2.5 S/mm; and (2) high T/sub c/ superconducting long-distance interconnection lines driven by bipolar circuits with transconductance of 2.5 S/mm, unless such long lines can be overcome by new chip architectures.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Miniaturized hairpin resonator filters and their application to receiver front-end MICs

The authors describe the fundamental characteristics of miniaturized hairpin resonators having parallel coupled lines and show their applications to bandpass filters and receiver front-end microwave integrated circuits (MICs). A method for calculating filter coupling parameters using a general-purpose microwave circuit simulator is presented. The bandpass filters have a suitable structure for MICs, and their size is one-half that of conventional hairpin resonators without increasing insertion losses. Trial receiver front-end MICs using these filters have been developed and have shown good characteristics such as low noise and a high image suppression ratio. They are applicable to a frequency range above the L-band.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Spice simulation of PWM DC-DC convertor systems: voltage feedback, continuous inductor conduction mode

A simple and straightforward method is proposed for simulating the transient and small-signal responses of open and closed-loop switch-mode DC-DC convenors. The topologyindependent method hinges on the substitution of the switched inductor, fundamental in the realisation of suchsystems, by an equivalent circuit which represents its average behaviour. This permits simulation by a general-purpose electronic circuit simulator such as SPICE. The proposed approach is demonstrated by presenting the simulation results of a boost convertor.

Simulation-oriented noise model for MOS devices

A formula for the noise in MOS devices particularly suited to general-purpose circuit simulation programs is described. It is valid in every part of the MOS I-V curves. The expression for the thermal noise is derived from a theoretical analysis, and the flicker-noise expression is empiric.

Numerical modeling of vacuum systems using electronic circuit analysis tools

The analysis of large and complex high-vacuum systems is a tedious process, especially when distributed loads and pumps are involved. It has been suggested that by using the appropriate transformations, a vacuum system can be modeled as an electrical network. Well-developed numerical techniques exist for the computational characterization of electrical networks, often implemented in the form of a general purpose circuit simulation code. In this paper, a method is presented for the modeling of high-vacuum systems using a circuit analysis code. The method includes the capability to model outgassing, and to obtain the response of a system to transient and time-varying loads. An example is given of the analysis of a vacuum system with distributed pumps and distributed loads using the commonly available spice ii program. The use of this technique is expected to significantly reduce the effort required to analyze such systems as accelerators, storage rings, and process lines.

Simplified analysis off arbitrary switched-capacitor networks

A general method is presented which allows a closed-form analysis of switchedcapacitor (SC) networks with several phases, arbitrary duty cycles and with nonideal operational amplifiers. The method is based on a new equivalent representation of SC networks in the zdomain and on flow-graph techniques. The equivalent z-domain representations of SC networks proposed in this paper are compatible with classical circuit-theory considerations, and they are simpler and require a smaller number of elements than the equivalent circuits previously proposed. The usefulness and efficiency of the method proposed is illustrated with some examples. Moreover, it is shown how to transform the z-domain SC networks into equivalent time-continuous (analogue) circuits to analyse them in the frequency and/or time domain by use of conventional general-purpose circuit simulation programs. A user-ready implementation on SPICE is also proposed.

A nonlinear method to estimate model parameters of junction field-effect transistors

Describes a method to estimate the model parameters of junction-type field-effect transistors. The characteristics of the device under test are expressed by a nonlinear equivalent circuit with a dependent current source. To estimate all unknown parameters to specify the characteristics of the device, a measurement circuit is sequentially configured into three independent modes by a desk-top microcomputer. Raw data acquired in each measurement mode are sent to another computer to obtain a nonlinear estimation of the model parameters concurrently with data acquisition. The curves characterized by the estimated parameters are found to fit well to the original data. A newly designed jig for measurement (including relays to change the circuit mode) is developed utilizing the IEEE standard 488-bus system. In cooperation with additional measuring instruments, fully automated acquisition and estimation are made possible. Since estimated values of the parameters are stored by the multiuser, host computer with a device name, they are ready to be used for such a general purpose circuit simulation program as SPICE 2.

Computer simulation of cardiopulmonary resuscitation: computer analysis of a simple electrical model of the circulation.

Extensive research is being conducted to study the mechanism of blood flow during cardiopulmonary resuscitation (CPR). Recently, work has been published using a simple electrical model of the circulation to simulate the hemodynamics of CPR. This analog was a hard-wired circuit consisting of the heart and great vessels modeled as a resistive-capacitive network, pressure as voltage, blood flow as current, blood inertia as inductance and vascular valves as diodes. Such a model is useful for examining the physiology of various methods and techniques of CPR administration. In this investigation, a general purpose circuit simulation program, SPICE Version 2G.6, was used to analyze previously published CPR models. With minor modifications, the program was fully able to simulate the hard-wired circuits. The program is very flexible, allowing for easy model modification and a wide range of parameter values. In addition, the program offers the advantages of increased accuracy and low cost. Suggested future applications are for rapid evaluation of new CPR concepts.

Simple technique for analysis of SC networks using general-purpose circuit simulation programs

A new technique is proposed which enables the transformation of a large class of switched-capacitor (SC) networks into equivalent time-continuous (analogue) circuits to analyse them by use of standard, general-purpose circuit simulation programs such as SPICE It is based on a block partitioning, i.e. a total SC network is divided into small building blocks. It is shown how basic SC building blocks like integrators and summers can be modelled by equivalent two-ports containing only resistors, lossless transmission lines and current-controlled voltage sources. Furthermore, some new offset-free SC integrator schemes based on multi-step integration algorithms are also described.

Electronic circuit and system simulation with Astec 3

Astec 3 is a general-purpose analogue electronic circuit simulation package developed in France and available on IBM and DEC VAX computers. Designed for DC, AC and transient analysis, the system stands as a rival to the widely used SPICE. This article, the first of two on the system, outlines the general features of the Astec 3 simulation language.

Computer-aided design of power electronic circuits

The general purpose circuit simulation package SPICE is used as a design tool for power electronic circuits. The process involves simulation of the complete circuit in the microsecond timescale, by which circuit behaviour under different operating conditions can be studied. Semiconductor device models and interconnection inductances are examined. The simulation process is applied to a 50 kVA transistorised chopper circuit and the results are discussed and compared with experimental results.

A spatio-temporal model of the horizontal cell layer with membrane ionic currents and gap junctions

Action potential propagation in complex terminal arborizations was simulated using SPICE, a general purpose circuit simulation program. The Hodgkin-Huxley equations were used to simulate excitable membrane compartments. Conduction failure was common at branch points and regularly spaced boutons en passant. More complex arborizations had proportionally more inactive synapses than less complex arborizations. At lower temperature the safety factor for impulse propagation increased, reducing the number of silent synapses in a particular arborization. Small structural differences as well as minute changes in the discharge frequency of the action potential resulted in very different activation patterns of the arborization and terminal boutons. The results suggest that the structural diversity of terminal arborizations allows a wide range of presynaptic information processing. The results from this simulation study are discussed in the context of experimental results on the modulation of synaptic transmission.

Analysis of switched-capacitor networks using general- purpose circuit simulation programs

This paper presents a method for the analysis of switched-capacitor (SC) networks in the frequency and time domains by the use of general-purpose circuit simulation programs such as SPICE. It is shown how the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">z</tex> -domain equivalent circuit can be modeled exactly in the continuous-time domain using the lossless transmission line element of the simulation program to implement the required one-port storage element (storistor). The resulting continuous-time equivalent circuit retains the sample-data characteristics of the SC networks and is not restricted to frequencies below the Nyquist rate. It is also shown that the transmission line element can be used to simulate the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">(\sin x)/x</tex> effect on the frequency response of the SC network due to the sample-and-hold process. Examples of the simulation of simple SC networks with and without op amps using SPICE are given.