Since equations generated with KCL are in terms of currents going in and out of nodes, these currents, if their values are not known, need to be represented by the unknown variables (node voltages). In principle, nodal analysis uses Kirchhoff's current law (KCL) at N-1 nodes to get N-1 independent equations. Therefore, there are N-1 node voltages for a circuit with N nodes. : 2-8 - 2-9 For all nodes, except a chosen reference node, the node voltage is defined as the voltage drop from the node to the reference node. Nodal analysis uses the concept of a node voltage and considers the node voltages to be the unknown variables. Two circuits are said to be equivalent with respect to a pair of terminals if the voltage across the terminals and current through the terminals for one network have the same relationship as the voltage and current at the terminals of the other network. The solution principles outlined here also apply to phasor analysis of AC circuits. Analysis of a circuit consists of solving for the voltages and currents present in the circuit. If the sources are constant ( DC) sources, the result is a DC circuit. For instance, one might transform a voltage generator into a current generator using Norton's theorem in order to be able to later combine the internal resistance of the generator with a parallel impedance load.Ī resistive circuit is a circuit containing only resistors, ideal current sources, and ideal voltage sources. On the other hand, it might merely change the form into one in which the components can be reduced in a later operation. A particular technique might directly reduce the number of components, for instance by combining impedances in series. This can be done by replacing physical components with other notional components that have the same effect. Main article: Equivalent impedance transformsĪ useful procedure in network analysis is to simplify the network by reducing the number of components. These parameters can be impedances, but there is a large number of other approaches (see two-port network). The usual approach is to express the transfer function as a matrix of parameters. A three (or more) terminal component effectively has two (or more) ports and the transfer function cannot be expressed as a single impedance. one-port component), the current and voltage are taken as the input and output and the transfer function will have units of impedance or admittance (it is usually a matter of arbitrary convenience whether voltage or current is considered the input). Most often, an input port and an output port are discussed and the transfer function is described as gain or attenuation.įor a two-terminal component (i.e. The relationship of the currents and/or voltages between two ports. Often, "circuit" and "network" are used interchangeably, but many analysts reserve "network" to mean an idealised model consisting of ideal components. If there is any connection to any other circuits then a non-trivial network has been formed and at least two ports must exist. A circuit is, in this sense, a one-port network and is a trivial case to analyse. Two terminals where the current into one is identical to the current out of the other.Ī current from one terminal of a generator, through load component(s) and back into the other terminal. A conductor with a substantially zero resistance is considered to be a node for the purpose of analysis.Ī group of branches within a network joined so as to form a complete loop such that there is no other loop inside it. Except where stated, the methods described in this article are applicable only to linear network analysis.Ī device with two or more terminals into which, or out of which, current may flow.Ī point at which terminals of more than two components are joined. There are many techniques for calculating these values however, for the most part, the techniques assume linear components. Network analysis is the process of finding the voltages across, and the currents through, all network components. In electrical engineering and electronics, a network is a collection of interconnected components.
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