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Ever seen a really hot model? No, not that kind of model - the kind of model meant here is the simulation of a circuit with electrical current and dependent voltage running through it.
Developed by the EECS Department of the University of California at Berkeley, SPICE is a simulator designed to analyze linear and non-linear current flow through devices with big-sounding names that range from resistor and uniform distributed RC model to metal-oxide-semiconductor field-effect transistor (MOSFET) and bipolar junction transistor (BJT). Since about 2002 it has been at version 3, aka SPICE3.
So how exactly does it work? Well, it begins with the order of analysis. For the most part, this includes:
- Direct Current
- Alternating Current Small-Signal
- Transient
- Pole-Zero
- Distortion
- Sensitivity
- Noise
An important facet of SPICE is that Direct Current analysis must take place before transient and AC Small-Signal, because the starting point is with shorted inductors and open capacitors. The AC Small-Signal then takes the information from the first test, and runs a range of frequencies over the linear circuit produced from its programming. The transient analysis determines transient output variables automatically from the DC analysis. The phases continue similarly through the remainder of the analyses as listed above.
The interesting thing to note about SPICE is that the commands utilized in it aren't all that much different from what you would see in a normal programming language. The SPICE3 language has keywords such as Display, Echo, Load and Write; it also has control structures like If Then Else, Goto and Break (think case switching in the that latter one, say in C++ or Java). Interestingly, Spice3 and Nutmeg (interpretative back end and standalone front end, respectively) do their circuit plotting through the X Window System. (Linux, anybody?) It also has pre-named variables, and data types like <= (less than or equal to) and ! (not).
Variations and permutations of SPICE are widely available in today's industry. There's no question you can SPICE up your models utilizing this technology. A Google search is highly recommended to review those companies that provide variations focused toward your assessment and modeling requirements.
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