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1176 ⏐⏐⏐ SYSTEM ANALYSIS: AN INTRODUCTION
I1 = 0
1
+
E 1
–
1′
System
The hybrid equivalent circuit appears in Fig. 26.50. Since the unit of
measurement for each term of Eq. (26.40a) is the volt, Kirchhoff’s voltage
law was applied in reverse to obtain the series input circuit indicated.
The unit of measurement of each term of Eq. (26.40b) has the
units of current, resulting in the parallel elements of the output circuit
as obtained by applying Kirchhoff’s current law in reverse.
1 +
I 1
E 1
1′ –
h 11
+
h12E2 –
FIG. 26.49
h 22 determination.
h 21 I 1
I 2
2
2′
h 22
FIG. 26.50
Two-port, hybrid-parameter equivalent network.
Note that the input circuit has a voltage-controlled voltage source
whose controlling voltage is the output terminal voltage, while the output
circuit has a current-controlled current source whose controlling
current is the current of the input circuit.
+
–
E 2
I 2
2
+
E 2
–
2′
EXAMPLE 26.10 For the hybrid equivalent circuit of Fig. 26.51:
E s
R s
+
–
I 1
+
Z i
E 1
–
h i
+
hrE2 –
h f I 1
FIG. 26.51
Example 26.10.
a. Determine the current ratio (gain) A i � I 2/I 1.
b. Determine the voltage ratio (gain) A v � E 2/E 1.
1
h o
I 2
+
E 2
–
Z L