In the circuit study it is very common to have coupling between a source coupled to a pair of terminals and a connected load on another pair of terminals. Between them there may be a complex structure . This structure can be treated like a black box no matter what it has inside it. These structures are called quadripoles and can be modeled through matrices, thus facilitating the study of their behavior for different loads placed under different excitations. We see, in the Figure 30-01, a representation schematic of a quadripole.

To study the quadripoles we must consider some basic hypotheses:

Therefore, depending on what mathematical relationships we make between the currents and voltages of the input and output ports, we can have several Parameters of Quadripoles. In the next chapters we will study some of the main parameters related to quadripoles.

When studying quadripoles we easily verify that all sets of pairs of equations that define each type of quadripole involve the same variables. Thus, the parameters associated with any pair of equations must be related to the parameters of all other pairs. In other words, knowing a set of parameters, we will be able to determine all the other parameters. For simplicity, we will present these relationships in a table.

However, before presenting the table, let's define some values that will appear when calculating the parameters. Are they: