Two port electrical network explanation

1. TWO-PORT NETWORKS
In many situations one is not interested in the internal organization of a
network. A description relating input and output variables may be sufficient
A two-port model is a description of a network that relates voltages and currents
at two pairs of terminals
Admittance parameters
Impedance parameters
Hybrid parameters
Transmission parameters
LEARNING GOALS
Study the basic types of two-port models
Understand how to convert one model into another

2. ADMITTANCE PARAMETERS
The admittance parameters describe the currents in terms of the voltages
2221212
2121111
VyVyI
VyVyI

 The first subindex identifies
the output port. The second
the input port.
1porttoappliedisvoltage
aandcircuited-shortisport
thewhen2portintoflowing
currentthedetermines21y
The computation of the parameters follows directly from the definition
02
1
12
01
1
11
12 

VV
V
I
y
V
I
y
02
2
22
01
2
21
12 

VV
V
I
y
V
I
y
The network contains NO independent sources

3. The computation of the parameters follows directly from the definition
02
1
12
01
1
11
12 

VV
V
I
y
V
I
y
02
2
22
01
2
21
12 

VV
V
I
y
V
I
y
Y11 is short circuit input admittance
Y12 and y21 are short circuit transfer admittance
Y22 is short circuit output admittance

4. LEARNING EXAMPLE Find the admittance parameters for the network
2221212
2121111
VyVyI
VyVyI


][
2
3
)
2
1
1( 1111 SyVI 
2111, yydeterminetousedCircuit
2I


 1212
2
1
21
1
VIII ][
2
1
21 Sy 
2212, yydeterminetousedCircuit
][
6
5
3
1
2
1
2222 SyVI 






][
2
1
65
53
32
3
12221 SyVII 





Next we show one use of this model