Two-Port Networks

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Two-Port Networks

• Chapter 19

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19.1 Introduction

• A two-port Network is an electrical network with
  two separate ports for input and output.

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19.2 Impedance Parameters
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• z11 Open-circuit input impedance
• z12 Open-circuit transfer impedance from port 1
  to port 2
• z21 Open-circuit transfer impedance from port 2
  to port 1
• z22 Open-circuit output impedance

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Fig 19.3
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19.4
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Fig 19.5
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Fig 19.6
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Example 19.1

• Determine the z parameters for the circuit in
  Fig. 19.7.

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Example 19.1 PSpice
To find Z parameters Example 9.1 .Param
Current_at_port21 port2 0 inject 0 A at
port 2 1st row port2 1 inject 1 A at port
2 2nd row I1 0 1 DC 1-Current_at_port2
R1 1 1x 20
R2 1x 0 40 R3 1x 2 30
I2 0 2 DC Current_at_port2 Vd
ummy 100 0 DC 1 .DC Vdummy 1 1 1 .STEP PARAM
Current_at_port2 LIST 0 1 .PRINT DC V(1) V(2) .END
We need to edit here for different circuits
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The Results
z11
z21
z12
z22
3.000E01 2.000E01
2.000E01 5.000E01
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19.3 Admittance Parameters
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• y11 Short-circuit input admittance
• y12 Short-circuit transfer admittance from port
  1 to port 2
• y21 Short-circuit transfer admittance from port
  2 to port 1
• y22 Short-circuit output admittance

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Fig 19.13
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Example 19.3

• Obtain the y parameters for the ? network shown
  in Fig. 19.14.

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Example 19.3
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Example 19.3
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Example 19.3
To find y parameters Example 19.3 .Param
Voltage_at_port20 port2 0 apply 0 V at
port 2 to find 1st row port2 1 apply 1 V
at port 2 to find 2nd row V1 1x 0 DC
1-Voltage_at_port2 Vport1 1x 1
R1 1 0 4 R2 1
2 2 R3 2 0 8
Vport2 2x 2 V2 2x 0 DC
Voltage_at_port2 Vdummy 100 0 DC 1 .DC Vdummy 1
1 1 .STEP PARAM Voltage_at_port2 LIST 0 1 .PRINT
DC I(Vport1) I(Vport2) .END
We just need to edit here for different networks.
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The Results are
y11
y21
y12
y22
7.500E-01 -5.000E-01
-5.000E-01 6.250E-01
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Example 19.4

• Determine the y parameters for the T network
  shown in Fig. 19.17.

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Example 19.4
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Example 19.4
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Example 19.4
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Example 19.4
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PSpice
To find y parameters Example 19.3 .Param
Voltage_at_port20 port2 0 apply 0 V at
port 2 to find 1st row port2 1 apply 1 V
at port 2 to find 2nd row V1 1xx 0 DC
1-Voltage_at_port2 Vport1 1xx
1
R1 1 1x 8 R2 1x 0 2 R3 1x 2 4 F1 1x 2 Vport1
2
Vport2 2xx 2 V2 2xx 0 DC Voltage_at_port2 V
dummy 100 0 DC 1 .DC Vdummy 1 1 1 .STEP PARAM
Voltage_at_port2 LIST 0 1 .PRINT DC I(Vport1)
I(Vport2) .END
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The Results are
y11
y21
1.500E-01 -2.500E-01
y12
y22
-5.000E-02 2.500E-01
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19.4 Hybrid Parameters
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• h11 Short-circuit input impedance
• h12 Open-circuit reverse voltage gain
• h21 Short-circuit forward current gain
• h22 Open-circuit output admittance

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Fig 19.20
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Example 19.5

• Find the hybrid parameters for the two-port
  network of . 19.22.

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Example 19.5
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Example 19.5
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Fig 19.31
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• a Open-circuit voltage gain
• b Negative short-circuit transfer impedance
• c Open-circuit transfer admittance
• d Negative short-circuit current gain

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Example 19.8

• Find the transmission parameters for the two-port
  network in Fig. 19.32

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Example 19.8
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Example 19.8
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19.6 Relationships Between Parameters
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Example 19.10

• Find z and g of a two-port network if
• Solution

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Example 19.10
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19.7 Interconnection of Networks
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Example 19.12

• Evaluate V2/V1 in the circuit in Fig. 19.42.

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Example 19.12
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Example 19.12
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Example 19.13

• Find the y parameters of the two-port in Fig.
  19.44.

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Example 19.14

• Find the transmission parameters for the circuit
  in Fig. 19.46.