# Equations

Discussion in 'General Electronics Chat' started by goodwin, May 4, 2010.

1. ### goodwin Thread Starter New Member

Apr 25, 2009
4
0
Hi

Can anyone provide the necessary equations to design a circuit

2. ### Wendy Moderator

Mar 24, 2008
20,772
2,540
Way too open a question to answer intelligently. Try Ohm's Law, it is the first of many taught, and a lot of experienced students still have trouble applying it occasionally.

If you want to learn electronics there is no easy path. You must read, and read, experiment, then read again.

It just so happens that this site is designed around a fairly good text book (which is still a work in progress). I would recommend reading, then coming back and ask more specific questions.

3. ### kkazem Active Member

Jul 23, 2009
160
28
HI,
If someone could provide the necessary equations to design a circuit, there would be no need for us electrical engineers to spend 4-5 years at university plus have electronics be our hobby as well. Most people (80-90%) who graduate with a B.S.E.E. degree wind up in one of two jobs: 1) As a technical salesman or 2) as a technician.
You have to have lots and lots of hands-on experience designing circuits, learning from your mistakes like me with literally bags full of blown-up transistors to better understand how to properly design circuits. If it were strictly equation-oriented, a computer could do it.
There is one difference these days and that's that students can learn without a lab and expensive equipment by using the numerous computerized circuit simulators that will show you whether your circuit works or not and give you the same type of waveforms from your circuit that a \$50,000 scope would if you actually built the circuit to test it out physically. The simulators save, mostly SPICE-based from U.C. Berkeley in the 70's I think. They have been improved such that all a user needs do is input a schematic, tell it how long you want it to run, input any other important or necessary parameters for your circuit, then look at whatever waveform you want to, including performing waveform math, like multiplying a voltage and a current waveform one point at-a-time to get a power waveform. And the best part is that they are now free of charge, like Linear Technology Corp's LTSPICE IV that anyone can download without charge and includes a fairly big library of parts well modeled after the real thing.

However, even using simulators, one needs design insight and at least basic knowledge of circuit theory, like Ohms law, Kirchoff's voltage law, Kirchoffs current law, Thevenin equivalents, the voltage and current divider rules, and many others that should be able to be rattled off the engineers mouth at will without having to think about it or look it up. These are just the very basic equations.

Regards,
Kamran Kazem