Circuit Equation Derivation Consideration

Once a while it is useful to be able to derive the circuit equation, this will ease the design process. Below are some points to consider when performing circuit equation derivation:

1.       If you already know the purpose of circuit, use that info to do the derivation.

2.       Most circuit can be modeled as y = mx +c, so you must define what is desired x (input) and y (output) prior to the actual derivation itself.

3.       Keep all variable names short – to ease your derivation.

4.       Always try to inspect the circuit and equation for opportunity to simplify the equation.

a.       For example, if a group of terms keep repeating itself, use a new term to represent them.

b.      Sometimes it is easier and more intuitive to use current as your parameter.

5.       Acknowledge characteristic of circuit component – such as

a.       Opamp input pins will generally be at the same potential (hence the term “virtual ground” for inverting Opamp with non-inverting pin tied to “Ground”.

b.      Base emitter of BJT will always be a diode drop.