Superposition and the Extra Element Theorem

When dealing with more than one input, the superposition theorem occupies the top of the list as its extension naturally leads to the Extra Element Theorem (EET). By first introducing superposition theorem in a simple and graphical way, this chapter paves the way towards the EET understanding in a hopefully simple and intelligible manner. In a linear circuit involving more than one individual source, superposition theorem states that the response, a current or a voltage, in a branch is the algebraic sum of the responses obtained from each of the individual sources while the other sources are turned off. SPICE is an excellent resource to verify calculations either obtained by hand or from a mathematical solver. The chapter also summarizes the different forms of EET and how people can combine time constants to form the numerator (zero) and the denominator (pole) of the transfer function under study.