We shall define a linear circuit as any circuit containing nothing but linear elements and independent sources. As examples, almost all the circuits we have considered thus far are linear circuits. Indeed, our attention throughout this text will be exclusively limited to linear circuits. The reasons for the focus on linear circuits are twofold: first, a great many interesting circuits, such as amplifiers, are linear and, second, the techniques for analyzing linear circuit are very powerful and from the basis for all circuit analysis whether linear or nonlinear. The analysis equations of a linear circuit are obtained by applying KVL , KCL and the element laws for each element in the circuit. The equations that result can be generally expressed as