Analog electronics

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 =^Y₂₁^V₁ +^Y₂₂^V₂                                                      -------  (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.