Section 2.5 Superposition Theorem
The superposition theorem isn’t often used on its own in circuit analysis, but is the foundation for some other very important rules and theorems. Before stating the superposition theorem, we must first establish a few definitions.
First, linear circuit elements are circuit elements for which the relationship between voltage and current is a linear function. Examples of linear circuit elements include resistors, capacitors, and inductors. A linear circuit contains only linear elements.
With these definitions in place, the superposition theorem states that for any linear circuit containing more than one independent source, the circuit can be solved for one source while turning the others `off’. Then, this can be repeated for each source and add the results together. When we talk about turning a voltage source off, we mean that we replace it in our analysis with a wire. Turning a current source off means replacing the current source with a break in the circuit. The superposition theorem in electronics arises directly from use of the superposition principle in electricity and magnetism.
