Simulators Berkeley SPICE

Since its introduction in 1971, SPICE (Simulation Program with Integrated Circuit Emphasis) has become the most popular analog simulation tool in use today. In the last 15 years, we have seen explosive growth in the use of SPICE, with the addition of Berkeley SPICE 3 enhancements, and support for C code model and mixed-mode simulation using XSPICE (Cox et al. 1992, Kielkowski 1994).We have also seen many new companies emerge as developers of SPICE-based simulation tools, most of which are currently available for the PC platform. 

Each vendor of SPICE simulation software has added features such as Monte Carlo analysis, schematic entry, and post simulation waveform processing, as well as extensive model libraries. In most cases, the manufacturers have modified the algorithms for controlling convergence and have added new parameters or syntax for component models. As a result, each electronic design automaton (EDA) tool vendor has the basic Berkeley SPICE 2 features and a unique set of capabilities and performance enhancements. 

We have made a reasonable effort to make apples to apples comparisons between the simulation speeds of the software in this book by using commonly available Berkeley SPICE 2 OPTIONS. The reader will notice that it is not predictable which software package will run the fastest on any given circuit. The real purpose of including the run times is to provide the user with an estimate as to how long the circuit will take to simulate on his or her own computer, nothing more. That being said, the simulation times noted after the simulations are reasonably accurate. 

Understanding the development of SPICE is useful in making a worthwhile comparison of vendor-offered simulation software. The foundation of many vender-offered simulators is Berkeley SPICE 3F.5 combined with XSPICE from the Georgia Institute of Technology. XSPICE is an add-on to SPICE 3, enhancing it with several key features, including a mixed-mode simulation capability (true digital simulator) and over 40 new primitive functional blocks such as Laplace and state machine elements. 

Users can create their own models, but most of the time they will depend on the model libraries provided by a vendor. The library models that do not use pure Berkeley SPICE 2G.6 syntax are unique to that particular simulator. While the SPICE syntaxes of each product are similar, they are not exactly compatible both distinct and subtle differences exist. However, in many cases, most models in vendors libraries have been provided by the component manufacturers. These models are available for free on the Internet. 

The three simulators have slightly different switch models. The IsSpice model used is the PSW1 switch. This is different from the built-in switch model, which is basically the Berkeley SPICE switch model with hysteresis. The parameters passed are VON = 7 V, RON = 100 Q, VOFF = 2 V, and ROFF = 100 . The PSpice simulation used a model called Sbreak. Like the PSW1 and the Micro-Cap switch models, this switch transitions smoothly between the on and off states and has no hysteresis. 

Thanks to Ron Rohrer, Larry Nagel, and all the students at the University of California, Berkeley, who worked hard in 1969 and 1970 to develop the first computer simulation software, Cancer (Computer Analysis of Non-Linear Circuits Excluding Radiation). This effort would result in the release of SPICE into the public domain in 1971. 

Nagel L.W., SPICE (simulation Program with Integrated Circuit Emphasis), Tech. Rep. ERL-m382-1977, Electronics Research laboratory, University of California, Berkeley (1977)... 

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