1. Two-Port Networks
Chapter 19

2. 19.1 Introduction
A two-port Network is an electrical network with two separate ports for input and output.
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3. 19.2 Impedance Parameters
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4. 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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5. Fig 19.3
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6. 19.4
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7. Fig 19.5
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8. Fig 19.6
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9. Example 19.1 Determine the z parameters for the circuit in Fig. 19.7.
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10. Example 19.1: PSpice To find Z parameters **Example 9.1
.Param Current_at_port2=1
**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}
Vdummy 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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11. ch19 Two-Port Networks

12. ch19 Two-Port Networks

13. ch19 Two-Port Networks

14. The Results z11 z12 z21 z22 3.000E+01 2.000E+01 2.000E+01 5.000E+01
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15. 19.3 Admittance Parameters
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16. 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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17. Fig 19.13
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18. Example 19.3
Obtain the y parameters for the  network shown in Fig
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19. Example 19.3
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20. Example 19.3
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21. Example 19.3
To find y parameters
**Example 19.3
.Param Voltage_at_port2=0
**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
**************************************************** R R R
Vport2 2x 2
V2 2x 0 DC {Voltage_at_port2}
Vdummy 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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22. ch19 Two-Port Networks

23. ch19 Two-Port Networks

24. ch19 Two-Port Networks

25. The Results are y11 y12 y21 y22 7.500E-01 -5.000E-01
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26. Example 19.4
Determine the y parameters for the T network shown in Fig
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27. Example 19.4
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28. Example 19.4
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29. Example 19.4
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30. Example 19.4
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31. PSpice
To find y parameters
**Example 19.3
.Param Voltage_at_port2=0
**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}
Vdummy 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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32. ch19 Two-Port Networks

33. ch19 Two-Port Networks

34. ch19 Two-Port Networks

35. The Results are y11 y12 y21 y22 1.500E-01 -2.500E-01
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36. 19.4 Hybrid Parameters
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37. 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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38. Fig 19.20
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39. Example 19.5
Find the hybrid parameters for the two-port network of
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40. Example 19.5
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41. Example 19.5
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42. Fig 19.31
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43. 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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44. Example 19.8
Find the transmission parameters for the two-port network in Fig
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45. Example 19.8
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46. Example 19.8
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47. 19.6 Relationships Between Parameters
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48. Example 19.10 Find [z] and [g] of a two-port network if Solution:
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49. Example 19.10
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50. 19.7 Interconnection of Networks
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51. Example 19.12 Evaluate V2/V1 in the circuit in Fig. 19.42.
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52. Example 19.12
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53. Example 19.12
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54. Example 19.13 Find the y parameters of the two-port in Fig. 19.44.
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55. Example 19.14
Find the transmission parameters for the circuit in Fig
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