Simulation software is based on the process of imitating a real phenomenon with a set of mathematical formulas. It is, essentially, a program that allows the user to observe an operation through simulation without actually running the program. Simulation software is used widely to design equipment so that the final product will be as close to design specs as possible without expensive in process modification.
Advanced computer programs can simulate weather conditions, electronic circuits, chemical reactions, atomic reactions, even biological processes. In theory, any phenomena that can be reduced to mathematical data and equations can be simulated on a computer. In practice, however, simulation is extremely difficult because most natural phenomena are subject to an almost infinite number of influences. One of the tricks to developing useful simulations, therefore, is to determine which are the most important factors.
In addition to imitating processes to see how they behave under different conditions, simulations are also used to test new theories. After creating a theory of causal relationships, the theorist can codify the relationships in the form of a computer program. If the program then behaves in the same way as the real process, there is a good chance that the proposed relationships are correct.
Electronics simulation software utilizes mathematical models to replicate the behaviour of an actual electronic device or circuit. Essentially, it is a software program that converts your computer into a fully functioning electronics laboratory. Electronics simulators such as CircuitLogix integrate a schematic editor, SPICE simulator and on-screen waveforms and make “what-if” scenarios easy and instant. By simulating a circuit’s behaviour before actually building it greatly improves efficiency and provides insights into the behavior and stability of electronics circuit designs. Most simulators use a SPICE engine that simulates analog, digital and mixed A/D circuits for exceptional power and accuracy. They also typically contain extensive model and device libraries. While these simulators typically have printed circuit board (PCB) export capabilities, they are not essential for design and testing of circuits, which is the primary application of electronic circuit simulation.
While there are strictly analog <ref>Mengue and Vignat, Entry in the University of Marne, at Vallee</ref>. electronics circuit simulators, such as LTSPICE, the most popular simulators on the market, such as Multisim and CircuitLogix, include both analog and event-driven digital simulation<ref>P. Fishwick, Entry in the University of Florida</ref>. capabilities, and are known as mixed-mode simulators <ref> J. Pedro and N. Carvalho, Entry in the Universidade de Aveiro, Portugal</ref>. This means that any simulation may contain components that are analog, event driven (digital or sampled-data), or a combination of both. An entire mixed signal analysis can be driven from one integrated schematic. All the digital models in mixed-mode simulators provide accurate specification of propagation time and rise/fall time delays.
The event driven algorithm provided by mixed-mode simulators is general purpose and supports non-digital types of data. For example, elements can use real or integer values to simulate DSP functions or sampled data filters. Because the event driven algorithm is faster than the standard SPICE matrix solution simulation time is greatly reduced for circuits that use event driven models in place of analog models <ref> L. Walken and M. Bruckner, Event-Driven Multimodal Technology</ref>.
Mixed-mode simulation is handled on three levels; (a) with primitive digital elements that use timing models and the built-in 12 or 16 state digital logic simulator, (b) with subcircuit models that use the actual transistor topology of the integrated circuit, and finally, (c) with In-line Boolean logic expressions.
Exact representations are used mainly in the analysis of transmission line and signal integrity problems where a close inspection of an IC’s I/O characteristics is needed. Boolean logic expressions are delay-less functions that are used to provide efficient logic signal processing in an analog environment. These two modeling techniques use SPICE to solve a problem while the third method, digital primitives, use mixed mode capability. Each of these methods has its merits and target applications. In fact, many simulations (particularly those which use A/D technology) call for the combination of all three approaches. No one approach alone is sufficient.