Figure 9-2 X shows a y-parametric lot”adjectival circuit that can be substituted fur any network or electronic device whose y-paramountcy values arc known. Notice that we have shown impedance blocks on the diagram. in keeping with the usual practice of representing impedance on a schematic diagram. In many books these blocks are labeled y; and y,,, a practice that could mistakenly lead a reader to believe that impedance having values y; and v; belong in the equivalent circuit. Do not he confused by that practice. It is easy to show that the circuit in Figure 9-28 has the same y parameters as the circuit to which it is equivalent. For example. if 02 = O. then the current source. labeled y,V2. is an ope” circuit, and the input admittance is clearly y;. The reader should verify that the other y parameters of the circuit similarly satisfy their respective definitions. Figure 9-29 shows the v-parametric equivalent circuit when a signal source having source impedance Z, is connected across the input and a load impedance ZL is connected across the output. We will obtain general expressions for the input and output impermanence and for the voltage and current gains of this circuit.
The output voltage 112 equals the parallel equivalent impedance Co and ZL multiplied by the current produced in the source labeled y Nate (hat the source produces a vole polarity Q that subsume Thus Given the v-parameter values of a circuit. The parallelogram values can be calculate, and vice versa. Table 9-3 gives the conversion relationships for the two sets