2. Two – Port Network

2.2. Admittance Parameters

:    The admittance parameters of a linear two port network may also be defined in the similar fashion as the impedance parameters discussed above. In the admittance parameters, variables V1 & V2 are assumed independent variables and I1 & I2 as the dependent variables. The dependent variables I1 & I2 may be defined as a linear function of Independent variables V1 & V2 as 

                                                 I1 = f1 ( V1, V2 )

                                    I2 = f2 ( V1, V2 )                                                            -------  (2.5)

and                               I1 =Y11V1 +Y12V2         

                                      I2 =Y21V1 +Y22V2                                                      -------  (2.6)

            In the matrix form it is given by :

                                              I1    Y11     Y12 V1

                                     =                                                  ------  (2.7)

                                             I 2    Y21     Y22 V2

  Where Y’s are the admittance (conductance for d. c.) parameters, which may be defined as :

                                                     Y 11 =, is the input admittance when output is short

V 2 = 0

circuited or short- circuit input admittance.

                                                  Y 12 = , is the reverse transfer admittance when input is

V 1 = 0

short circuited or short circuit reverse transfer admittance.

                                                 Y 21 =, is the forward transfer admittance when output is

V 2 = 0

short circuited or short circuit forward transfer admittance.

and                               Y 22 =                     , is the output admittance when input is short

V 1 = 0

circuited or short circuit output admittance.

 These Y – parameters are also called as short circuit parameters as given in the network either input or output is shorted. The equivalent circuit of the network using Y- parameters is given in figure2.3.