nodal analysis
NODAL ANALYSIS
DESCRIPTION
EXAMPLES WITH INDEPENDENT SOURCES
SUPERNODE
EXAMPLES WITH DEPENDENT SOURCES
SUMMARY
DESCRIPTION
Nodal analysis is more commonly used than mesh or loop analysis for analysing networks. It can be used to determine the unknown node voltages of both planar and non-planar circuits. Nodal equations are usually formed by applying
Kirchoff’s Current Law to the nodes with unknown voltages, whereas equations based on Kirchoff’s Voltage Law are used to form the mesh equations. In order to apply nodal analysis to a circuit, the first step is to select a reference node or datum node and then assign a voltage at each of the other nodes with respect to the reference node. In a circuit with dc sources, the node that has the lowest voltage is usually selected as the reference node and then the other node voltages would be positive. Often the node that has the maximum elements connected to it in a circuit tends to be the reference node. Many electronic circuits have a metallic chassis and the reference node, usually the negative terminal of the dc source present in the circuit, happens to be connected to the chassis. It is common practice to connect the chassis to earth terminal of the utility supply. Then the reference node is at earth or ground potential and hence the reference terminal is referred to as the ground terminal, even if it is not earthed. In a power system, the casing of power appliances is usually earthed and the neutral of the utility supply remains connected to earth at the source. The reference node in such a power system is then at zero potential.
In nodal analysis, the voltage at the reference node is assumed to be zero. The voltages at other nodes are expressed with reference to the datum node. Since the unknown node voltages are determined by nodal analysis, it is logical to write the
KCL equations at nodes. The procedure can be summarized as follows.
!
!
!
!
Select a reference node and treat it to
DESCRIPTION
EXAMPLES WITH INDEPENDENT SOURCES
SUPERNODE
EXAMPLES WITH DEPENDENT SOURCES
SUMMARY
DESCRIPTION
Nodal analysis is more commonly used than mesh or loop analysis for analysing networks. It can be used to determine the unknown node voltages of both planar and non-planar circuits. Nodal equations are usually formed by applying
Kirchoff’s Current Law to the nodes with unknown voltages, whereas equations based on Kirchoff’s Voltage Law are used to form the mesh equations. In order to apply nodal analysis to a circuit, the first step is to select a reference node or datum node and then assign a voltage at each of the other nodes with respect to the reference node. In a circuit with dc sources, the node that has the lowest voltage is usually selected as the reference node and then the other node voltages would be positive. Often the node that has the maximum elements connected to it in a circuit tends to be the reference node. Many electronic circuits have a metallic chassis and the reference node, usually the negative terminal of the dc source present in the circuit, happens to be connected to the chassis. It is common practice to connect the chassis to earth terminal of the utility supply. Then the reference node is at earth or ground potential and hence the reference terminal is referred to as the ground terminal, even if it is not earthed. In a power system, the casing of power appliances is usually earthed and the neutral of the utility supply remains connected to earth at the source. The reference node in such a power system is then at zero potential.
In nodal analysis, the voltage at the reference node is assumed to be zero. The voltages at other nodes are expressed with reference to the datum node. Since the unknown node voltages are determined by nodal analysis, it is logical to write the
KCL equations at nodes. The procedure can be summarized as follows.
!
!
!
!
Select a reference node and treat it to