Z Parameter of two port network

Hello friends, in this article we will study about Z Parameter of two port network.

Z-Parameter is also called "Open Circuit Parameter" and "Impedance Parameter".


In Z-Parameter, the input and output voltage are function of input and output current.
( V1 , V2 )      =        f ( I1 , I2 )

It can also be written as:
[V] = [Z]   [I]

 where Z represents Impedance Matrix.
In matrix form

[V1] =    [Z11  Z12]   [I1]
[V2] =    [Z21  Z22]   [I2]

Writing it in equation,
V1 = Z11* I1 + Z12* I2 .........eq1
V2 = Z21* I1 + Z22* I2 .........eq2


CASE-1 OPEN CIRCUITING THE OUTPUT PORT.

If the Output port of the two port network is open circuited then the output current is zero, i.e. I2 = 0.

Related pages
   � Y-PARAMETER OF TWO PORT NETWORK

OUTPUT PORT IS OPEN CIRCUITED

Now, equation 1 and 2 will be reduced to :
V1 = Z11* I1
V2 = Z21* I1

So, Z11 = V1/ I1    ( keeping I2 = 0 )
Z21 = V2/ I1  ( keeping I2 = 0 )

CASE-2 OPEN CIRCUITING THE INPUT PORT.

If the Input port of the two port network is open circuited then the input current is zero, i.e. I1 = 0.

INPUT PORT IS OPEN CIRCUITED

Now, equation 1 and 2 will be reduced to :
V1 = Z12* I2
V2 = Z22* I2

So, Z12 = V1/ I2    ( keeping I1 = 0 )
Z22 = V2/ I2  ( keeping I1 = 0 )

Z11 is called input driving point Impedance
Z12 is called forward transfer Impedance
Z21 is called reverse transfer Impedance
Z22 is called output driving point Impedance.

For a network to be symmetrical , Z11 = Z22
For a network to be reciprocal, Z12 = Z21

EQUIVALENT CIRCUIT OF Z-PARAMETER

EQUIVALENT CIRCUIT OF Z-PARAMETER

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