H-Parameter Of Two Port Network

In this article we will study about h-Parameter of two port network.

h-Parameter representation is widely used in modelling of electronic components and circuits, particularly transistors.

h-Parameter is called "Hybrid Parameter".

In h-Parameter, the input voltage and output current are function of input current and output voltage respectively.

( V1 , I2 ) = f ( I1 , V2 )
In matrix form,
[V1] =    [h11  h12]   [I1]
[I2] =     [h21  h22]   [V2]
Writing it in equation,
V1 = h11* I1 + h12* V2 .........eq1
I2 =  h21* I1 + h22* V2 .........eq2
CASE-1 SHORT CIRCUITING THE OUTPUT PORT
If the Output port of the two port network is  short circuited then output voltage is zero, i.e. V2 = 0.

Now, equation 1 and 2 will be reduced to :
V1 = h11* I1
I2 =  h21* I1
So, h11 = I1 /V1    ( keeping V2 = 0 )
      h21 = I2/ V1    ( keeping V2 = 0 )
CASE-2 OPEN CIRCUITING THE INPUT PORT
If the Input port of the two port network is open circuted then the input current is zero, i.e. I1 = 0.

Now, equation 1 and 2 will be reduced to :
V1 = h12* V2
I2 =  h22* V2
So, h12 = V1/ V2    ( keeping I1= 0 )
      h22 = V2/ I2   ( keeping  I1 = 0 )
h11 is called input impedance and its unit is ohm.
h12 is called forward current gain and is unitless.
h21 is called reverse voltage and is unitless.
h22 is called output impedance and its unit is mho.
For a network to be symmetrical,
h11*h22 - h12*h21 = 0. (h=0)
For a network to be reciprocal,  h12 = -h21
EQUIVALENT CIRCUIT OF Y-PARAMETER