Select a reference node. Label each node except the reference with a
If one end of a voltage source is connected to ground, label the other
end of the voltage source with the actual voltage (vS2 below).
If there is a voltage source not connected to ground, label the - end
with a letter (vA below), and label the + end with the voltage at the
- end plus the voltage of the source (
vA + vS1 below). This is
called a Supernode.
For each node except the reference node and nodes connected to voltage
sources write KCL in the form
where iOUT is written in terms of node voltages (e.g.,
for R4 below).
The nodal equation for node B below is
-vAG2 + vB (G2 + G3) = iS3 + vS1G2 + vS2G3
For nodes of the form of 1(a) there is no need to write KCL since the
voltage is already known.
For nodes of the form 1(b) write one KCL for both ends of the voltage
source. For example: