UNIT- 8
TWO PORT NETWORK PARAMETERS
Q.1) Explain Z and Yparameters with equivalent circuit. Also express Z- parameters in terms of Y – parameters. JUNE 2013
Ans. : z-parameters These are also called impedance parameters. These are obtained by expressing voltages at two ports in terms of currents at two ports. Thus, currents I1 and I2 are independent variables; while V1 and V2 are dependent variables .Thus, we have,
From above equations it is clear that z11 and z22 gives the relationship between voltages and currents at port 1 – 1’ and port 2-2’ respectively. Such parameters are the driving point impedances. While z12 and z21 gives the relationship between voltage and currents at different ports. Such parameters are the transfer impedances. Moreover, these parameters are defined only when the current in one of the ports is zero. This corresponds to the conditions that the one of the ports is open circuited. Hence z- parameters are named as open circuit impedance parameters. Hence we can write, z11 = Open circuit driving point input impedance z22 = Open circuit output impedance z12 = Open circuit forward transfer impedance
z21 = Open circuit reverse transfer impedance

The equivalent circuit of a two port network interms of open circuit impedance parameters satisfying equations (1) and (2) is as shown in the Fig.
These are also called admittance parameters. These are obtained by expressing currents at two ports in terms of voltages at two ports. Thus ports thus, voltages V1 and V2 are independent variables, I1 and I2 are dependent variables. Thus, we have
This is called short circuit driving point output admittance. These parameters are defined individually only when the voltage in any one of the ports is zero. This corresponds to the condition that one of the ports is short circuited. Hence y- parameters are also short circuit admittance parameters. The equivalent circuit of a two port network interms of short circuit admittance parameters satisfying equations (1) and
(2) is as shown in the Fig.

Q.2) Obtain y- parameters z- parameters in terms of y- parameters.
JUNE2013 , JUNE 2014

These are also called admittance parameters. These are obtained by expressing currents at two ports in terms of voltages at two ports. Thus ports voltages V1 and V2 are independent variables, I1 and I2 are dependent variables. Thus, we have
This is called short circuit driving point output admittance. These parameters are defined individually only when the voltage in any one of the ports is zero. This corresponds to the condition that one of the ports is short circuited. Hence y- parameters are also short circuit admittance parameters. The equivalent circuit of a two port network interms of short circuit admittance parameters satisfying equations (1) and (2) is as shown in the Fig. 27.

Q.3) Obtain y- parameters in terms of Z- parameters JUNE 2014

Q.4) Find the h- parameters of the network shown in Fig. Give its equivalent circuit. JAN.2014

Q.5) Find Y parameters for the network shown in fig. JUNE 2013, JAN 2014

Q.6) Find the transmission or general parameters for the circuit shown in Fig. JAN.2015

Q.7) Define y and z parameters. Derive relationship such that y parameters expressed in terms of z parameters and z parameters expressed in terms of y parameters . JULY 2013

8) Define h and T parameters and derive expressions for [h] in terms of [T]. JAN.2015

Q.9) A two port network, in terms of z-parameters is said to be symmetric if z11 = z22 and reciprocal if z12 = z21. Obtain the corresponding conditions in terms of i) h-parameters ii) T-parameters,
Using the relationship between different two port parameters. JAN.2014