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# Chapter 7 (Part 1) Two Port network - Notes, Circuit Theory, Electrical Engineering Electrical Engineering (EE) Notes | EduRev

## Electrical Engineering (EE) : Chapter 7 (Part 1) Two Port network - Notes, Circuit Theory, Electrical Engineering Electrical Engineering (EE) Notes | EduRev

The document Chapter 7 (Part 1) Two Port network - Notes, Circuit Theory, Electrical Engineering Electrical Engineering (EE) Notes | EduRev is a part of the Electrical Engineering (EE) Course Electrical Engineering SSC JE (Technical).
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Two Port network

• A pair of terminal through which a current may enter or leave a network is known as a port. Two-terminal devices or element (such as resistors, capacitors, and inductors) result in one-port  networks. 
• Here, we are mainly concerned with the twoport networks. A two-port network is an electrical network with two separate ports for input and output. Thus, a two-port network has two terminal pairs acting as access points. The current entering in the pair leaves the other terminal in the pair. Three-terminal devices such as transistors can be configured into two-port networks. 
• Armed only with the knowledge that the circuit is linear, and the ability to measure the voltage and currents, we will shortly see that it is possible to characterize such a network with a set of parameters that allows us to predict how the network will interact with other networks.

Network parameters 

• Z– parameters 
• Y= parameters 
• ABCD parameters (Transmission parameter) 
• A' B' C' D' parameters (Inverse transmission parameter) 
• h-parameters 
• g-parameters

Z – PARAMETERS  ....the input driving- point impedance with the output port open-circuited ...The reverse transfer impedance with the input port open-circuited .....the forward transfer impedance with the output port open .....the output driving point impedance with input port opencircuited

•  The equivalent circuit representation of equation
(i) is in figure below, where Z12 I2 and Z21 I1 are current controlled voltage sources (CCVS) 
• Rewriting equation (i),

V1 = (Z11 –Z12)I1+ Z12 (I1 + I2)
V2 = (Z21 – Z12) I1 + (Z22 –Z12)I+ Z12 (I1 + I2) ...........(ii)

• The equivalent circuit for equation (i) is given as, • The equivalent circuit for equation (ii) is given as, Condition of Reciprocity and Symmetry

Reciprocal Network 

• A network must be reciprocal when ratio of response at port 2 to the excitation at port '1' is same as ratio of response at port 1 to the excitation at port 2 Z11 = Z22

Y- PARAMETERS  .............(Because in Y11 we have short circuit condition whereas in Z11 we have open cuicuit condition) input driving point admittance .....(reverse transfer admittance) ....(forward transfer admittance) ...(o utput driv in g po in t admittance) Equivalent Circuit Y-parameter • Rewriting equation of Y-parameters

I1 = (y11 + Y12) V1 – Y12 (V1-V2)

I2 = (Y23 – Y12) V1 + (Y22 + Y12)V2 – Y12 (V2–V1)

For this equivalent II–network For reciprocal network Y12 = Y21
For sysmmetrical network Y11  = Y22

TRANSMISSION PARAMETERS (ABCD) V1 = AV2 + B (–12)
I1 = CV2 + D (–I2)

The transmission parameters are ..(i.e. the reverse voltage ratio with the receiving end open circuited) ..(i.e. the transfer admittance with the receiving end open-circuited) ....(i.e. the transfer impedance with the receiving end short-circuited ) ...(i.e. the  reverse  current ratio with the receiving end short circuited.)

Condition for Reciprocity Condition for Symmetry
A=D

INVERSE TRANSMISSION PARAMETERS
V2 = A'V+ B' (–I1) The inverse transmission parameter can be defined as ...(forward voltage ratio with sending end open circuited) ...(transfer admittance with sending end open circuited) ....(transfer impedance with sending end short circuited) ...(forward current ratio with sending end short circuited)

Condition of Reciprocity Condition for Symmetry

A' = D'

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