Lovely SPICE and Stupid SPICE

All electronic engineers know the marvelous CAD tool called “SPICE“ for circuit simulation. The SPICE is only one tool that provide the accurate values for simulation PROVIDED THAT WE HAVE ACCURATELY SPICED AND CONTROLLED...!

SPICE is a inbuilt mathematical tool which uses matrix of circuit nodes and perform the mathematical solution like numerical integration differentiation ...etc. The details like how it works can be googled for further reading.

My aim of this post is to tell wrong and right things with SPICE usage. Generally, people say if some one able to generate some waveforms using SPICE, he is a designer. In reality good designer never use SPICE . He uses his head, pencil and paper. SPICE is like any C program, if you give something as input, it always gives you some output. That is the reason why some designers says spice is a “Garbage in- Garbage out” program. But if you feed good things to it, definitely,it provides fruitful things.

Before proceeding with spice simulation it is better to understand the basic spice syntax. We need to know do's and don'ts . For example, the first line of the spice deck should be a comment,another example,to indicate 1E+6 symbolically we need to use MEG and not M(M stands for 1E-3). This kind of small mistakes can leads to waste of time and wrong results.

Presence of mind is very important. If we need to measure any parameter,we need to have proper set up. The set up can be done iff we are aware of what are expected results. For example, in order to measure set up or hold time of a circuit we need to give enough time in spice .tran command, and another example may be, the spice .tran run time should be greater than the time period of the clock if clock is exist in the design. This kind of awareness towards the spice deck is possible if we are well aware of what the circuit does. So I can say that SPICE helps us in the design of circuits if we are aware of circuit design.

My suggestion is, don't go to the computer unless you know what you are expecting. You need to have command over the circuit analysis, then test you abilities with spice.