by September 16, 2003 0 comments



Circuit boards used in common devices have a variety of components and traces packed into a tiny space. How are such circuits designed and implemented? The answer lies in software. Everything from designing the circuit to testing and implementing it can be done through specialized packages. We take a look at Multisim, a circuit design and simulation tool.

Since the actual package is huge and one can’t do justice to it in a single page review, we’ll take a look at the most essential components of the system.

Schematic capture
Circuits are built in Multisim using this particular module. It has a database of most of the commonly used components like resistors, diodes and ICs (9000 and 17000 in the Professional and Power Professional Editions, respectively) that can be placed and wired immediately. If the component that you are interested in is not available on the database, you can create your own by specifying its behavior or base it on some existing component. Clicking at any two end points results in a connecting wire between those two points. Components and wires can be moved, deleted or created at any point of time. Perhaps one of the most useful features is that a part of a circuit can be defined as a sub-circuit and replaced by a magic ‘box’.

This kind of abstraction is helpful while designing large or complex circuits. If changes need to be made to this sub-circuit, this box can be expanded and edited. Completed schematics can be exported to all major PCB layout software packagesincluding Electronics Workbench’s
Ultiboard. 

A class of components called ‘sources’ generate AC and DC currents and voltages, andclocks and pulses. AM and FM modulated sources for radio frequency design are also included. The parameters for these sources can be individually controlled via their property pages.

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N   A   P   S   H  
O   T

Price : Education edition: Rs 40,000; Power Professional: Rs 2.6 to 4.5 lakh (depending on add-ons); Professional version: Rs 1 to 2.6 lakh
Meant for : Electronic engineers
Key Specs : Range of components with simulation models, virtual instruments like four channel scope and frequency counter, hierarchical design capability and project browser
Contact : Trident Techlabs, Delhi.
Tel : 25939907. 
E-mail : corporate@tridenttechlabs.com 

Simulation
Simulation is a mathematical way of emulating the behavior of a circuit. With it, you can determine much of a circuit’s performance without physically constructing it. Multisim offers multiple simulation engines that can be used as per need. These are SPICE (Simulation Program with Integrated Circuit Emphasis) that has become an industry standard since its release in 1972, VHDL and Verilog HDL that are used to document and design electronic systems, and co-simulation of all three together. For example, digital circuits to be built as a PCB are generally best simulated with SPICE, whereas if they are implemented in Programmable Logic Devices VHDL or Verilog HDL are most commonly used. Simulations are interactive in Multisim. You can change the values of those components whose values can be controlled through the keyboard and see the simulation results instantly. There are also virtual instruments like oscilloscopes, spectrum analyzers, logic analyzers, wattmeters and multimeters that can be connected to the circuit to monitor its behavior. The results of circuit analysis can be exported to other applications like Excel and
Mathcad. 

Anuj Jain

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