Re: How to draw the small signal equivalent model of a circu
In a two-terminal network, the terminal voltage is related to the terminal current by the impedance Z =V/I. In a four-terminal network, if each terminal pair (or port) is connected separately to another circuit as in Fig. 1, the four variables i1, i2, v1, and v2 are related by two equations called the terminal characteristics. These two equations, plus the terminal characteristics of the connected circuits, provide
the necessary and sufficient number of equations to solve for the four variables.
The terminal characteristics of a two-port network, having linear elements and dependent sources, may be written in the s-domain using z-parameters as shown in eqt. (1).
The coefficients Zij have the dimension of impedance and are called the Z-parameters of the network. The Z-parameters are also called open-circuit impedance parameters since they may be measured at one terminal while the other terminal is open. They are given in eqt. (2)