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• Kirchoff’s current law: The algebraic sum of all currents entering
(exiting) a circuit node must be zero.

In-Class Exercise
Pb. 8.6 In a bridged-T filter, the voltage V (t) is the input voltage, and the out-
s
put voltage is that across the load resistor R . The circuit is given in Figure 8.3.
L

L

R 1 R 2

V s V
C R L out

FIGURE 8.3
Bridged-T filter. Circuit of Pb. 8.6.

Assuming that R = R = 3 Ω, R = 2 Ω, C = 0.25 F, and L = 1 H:
L
2
1
a. Write the equations for the phasors of the voltages and currents.
b. Form the matrix representation for the equations found in part (a).
V ˜
c. Plot the magnitude and phase of out as a function of the frequency.
V ˜
S
d. Compare the results obtained in part (c) with the analytical results
of the problem, given by:

V ˜ N ω
()
out =
()
V ˜ D ω
S
+
j R
N () =ω R R (R + R ) + ω 2 (L CR R )
2 L 1 2 2 1 L
D () =ω R [R R + R R − ω 2 LCR (R + R )]
2 1 L 2 L 1 2 L
+ jω [(L RR + RR + R R + 2 ]
) CR R R
1 2 1 L 2 L 1 2 L

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