1.2 ● Electronic simulation

transient, noise responses, Fourier spectrum, and numerous other responses of the circuit can be easily tabulated, plotted, or recorded.

Although simulation is an alternative and invaluable tool in designing and developing electronic circuits, it has the following advantages and disadvantages:

• Any component, whatever the cost, can be modelled and simulated using a simulator.

Virtual instruments are computer programs and thus there are no cost issues • Simulation does not usually take into consideration the component tolerances, aging, or temperature effects. Users may think that all components are ideal at all times • Virtual instruments and components used in a simulation can not be damaged by wrongly connecting or by applying large voltages or currents • Simulation results may not be accurate at very high frequencies. For example, concepts like the skin effect are not normally considered in high-frequency simulations • There are no calibration processes associated with virtual instruments. They are available at all times and operate with the same specifications • Simulation allows measurements of internal currents and voltages that in many cases can be near impossible to make using real components • Simulation can easily be used in distant education courses. Students can be supplied with copies of the simulator program, or they can be given access codes to use a simulator over the web (e.g. TINACloud). Experiments can then be carried at home and at times convenient to them • Simulation programs constantly evolve as new components are introduced by manufacturers. This requires software updates from time to time

1.2 ● Electronic simulation

The history of electronic simulation dates back to the 1970s. Before the availability of personal computers, electronic simulation was carried out in analog form using operational amplifiers and passive components. This type of simulation was very limited, was not accurate, and was mainly used in analysing automatic control systems.

One of the earliest simulation programs was the SPICE (Simulation Program with Integrated Circuit Emphasis), designed to simulate analog electronic circuits. Another circuit simulation program, CANCER was developed by Ronald Rohrer of U.C. Berkeley in the late 1960s. Although CANCER was improved in the early 1970s, it was rewritten and renamed SPICE version 1 after Rohrer left Berkeley. SPICE version 2 was then released as a public domain computer simulation program by professor Donald Pederson of Berkeley.

Version 3 of SPICE was released again as a public domain program in March of 1985. This version was written in FORTRAN which was the most commonly used programming language at the time.

Most professional electronic simulation programs nowadays are based on SPICE circuit modelling techniques. It is, therefore, worthwhile to look at the SPICE modelling very briefly as a matter of completeness. There are many sources of information such as books,