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After completing this chapter, students should be able to do the following:
• Describe the general features and the types of SPICE software.
• Describe the types of analysis that can be performed on electronic and electrical circuits.
• Describe the limitations of PSpice® software.
• List the online resources on SPICE.
1.1 INTRODUCTION
Electronic circuit design requires accurate methods of evaluating circuit performance. Because of the enormous complexity of modern integrated circuits, computer-aided circuit analysis is essential and can provide information about circuit performance that is almost impossible to obtain with laboratory prototype measurements. Computer-aided analysis makes possible the following procedures:
1. Evaluation of the effects of variations in elements, such as resistors, transistors, and transformers
2. Assessment of performance improvements or degradations
3. Evaluation of the effects of noise and signal distortion without the need for expensive measuring instruments
4. Sensitivity analysis to determine the permissible bounds determined by the tolerances of all element values or parameters of active elements
5. Fourier analysis without expensive wave analyzers
6. Evaluation of the effects of nonlinear elements on circuit performance
7. Optimization of the design of electronic circuits in terms of circuit parameters
SPICE (simulation program with integrated circuit emphasis) is a general-purpose circuit program that simulates electronic circuits. It can perform analyses on various aspects of electronic circuits, such as the operating (or quiescent) points of transistors, time-domain response, small-signal frequency response, and so on. SPICE contains models for common circuit elements, active as well as passive, and it is capable of simulating most electronic circuits. It is a versatile program and is widely used in both the industry and academic institutions.
Until recently, SPICE was available only on mainframe computers. In addition to the cost of the computer system, such a machine can be inconvenient for classroom use. In 1984, MicroSim introduced the PSpice simulator, which is similar to the Berkeley version of SPICE and runs on an IBM-PC or compatible, and is available free of cost to students for classroom use. PSpice thus widens the scope for the integration of computer-aided circuit analysis into electronic circuits courses at the undergraduate level. Other versions of PSpice, which run on the Macintosh II, 486-based processor, VAX, SUN, NEC, and other computers, are also available.
1.2 DESCRIPTIONS OF SPICE
PSpice is a member of the SPICE family of circuit simulators, all of which originate from the SPICE2 circuit simulator, whose development spans a period of about 30 years. During the mid-1960s, the program ECAP was developed at IBM [1]. In the late 1960s, ECAP served as the starting point for the development of the program CANCER at the University of California (UC) at Berkeley. Using CANCER as the basis, SPICE was developed at Berkeley in the early 1970s. During the mid-1970s, SPICE2, which is an improved version of SPICE, was developed at UC–Berkeley. The algorithms of SPICE2 are robust, powerful, and general in nature, and SPICE2 has become an industry standard tool for circuit simulation. SPICE3, a variation of SPICE2, is designed especially to support computer-aided design (CAD) research programs at UC–Berkeley. As the development of SPICE2 was supported using public funds, this software is in the public domain, which means that it may be used freely by all U.S. citizens.
SPICE2, referred to simply as SPICE, has become an industry standard. The input syntax for SPICE is a free-format style that does not require data to be entered in fixed column locations. SPICE assumes reasonable default values for unspecified circuit parameters. In addition, it performs a considerable amount of error checking to ensure that a circuit has been entered correctly.
PSpice, which uses the same algorithms as SPICE2, is equally useful for simulating all types of circuits in a wide range of applications. A circuit is described by statements stored in a file called the circuit file. The circuit file is read by the SPICE simulator. Each statement is self-contained and independent of every other statement, and does not interact with other statements. SPICE (or PSpice) statements are easy to learn and use.
A schematic editor can be used to draw the circuit and create a Schematics file, which can then be read by PSpice for running the simulation.
1.3 TYPES OF SPICE
The commercially supported versions of SPICE2 can be classified into two types: mainframe versions and PC-based versions. Their methods of computation may differ, but their features are almost identical. However, some may include such additions as a preprocessor or shell program to manage input and provide interactive control, as well as a postprocessor to refine the normal SPICE output. A person used to one SPICE version (e.g., PSpice) should be able to work with other versions.
Mainframe versions are
HSPICE (from Meta-Software), which is for integrated circuit design with special device models
RAD-SPICE (from Meta-Software), which simulates circuits subjected to ionizing radiation
IG-SPICE (from A.B. Associates), which is designed for “interactive” circuit simulation with graphics output
I-SPICE (from NCSS Time Sharing), which is designed for “interactive” circuit simulation with graphics output
Precise (from Electronic Engineering Software)
PSpice (from MicroSim)
AccuSim (from Mentor Graphics)
Spectre (from Cadence Design)
SPICE-Plus (from Valid Logic)
The PC versions include the following:
AllSpice (from Acotech)
Is-Spice (from Intusoft)
Z-SPICE (from Z-Tech)
SPICE-Plus (from Analog Design Tools)
DSPICE (from Daisy Systems)
PSpice (from MicroSim)
OrCAD (from Cadence)
Spice (from KEMET)
B2 Spice A/D (from Beige Bag Software)
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