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Unformatted text preview: QUIZ 6 FALL 2000 The circuit contains only dependent sources Determine the Thevenin equivalent at a  b.
Use a current probe
R2
a
R1
b a VP R2 This is the equivalent circuit.
We need to determine R_th b
Since we need to determine V_p and there are only two non
reference nodes we will use node analysis V1 +
VX
aVX
_ VP VP − V1
( R2 = 2 R1 )
+
= 0 /* R2
R1
R2
V −V
V
( R3 = 2 R2 )
@ V1 : − aVX + 1 P + 1 = 0 /* R3 = 4 R1
R2
R3
Controlling variable (in terms of node voltages): V X = VP
@ VP : − I P + R3 b 3VP − V1 = 2 R1 I P
− (2 + 4aR1 )VP + 3V1 = 0
Solve for V_p 6 R1 I P
VP =
7 − 4aR1 a R3 R 1 = , R2 = , R3 = , a = R1 IP +
VX
aVX
_ RTH RTH = VP
6 R1
=
I P 7 − 4aR1 R_1(k)
R_2(k)
R_3(k)
a (1/k)
R_Thev 1
2
4
1
2 2
4
8
0.5
4 QUIZ 6 FALL 2000 Find the Thevenin equivalent circuit at a  b
VS
supernode VOC V1 a + + aVX This the equivalent circuit to be determined +
VX
_ R RTH −
b VTH +
 RTH
b For open circuit voltage aVX + Controlling variable: V1 VOC
+
=0
R
R − V1 = VS VS
2 + aR R(k)
V_S{V]
a(1/k)
V_Thev
R_Thev VS
a + aVX VOC = V X = VOC R +
VX
_ VOC
=
I SC Only one supernode. Constraint due to source: VOC Zero current! VTH = VOC VOC R VS = , R = , a = KCL@ Supernode a R I SC
b Circuit for short circuit current VX = 0 I SC VS
=
R RTH = R
2 + aR 3
12
0.666667
3
0.75 4
24
0.5
6
1 ...
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This note was uploaded on 12/01/2011 for the course EE 2120 taught by Professor Aravena during the Fall '08 term at LSU.
 Fall '08
 ARAVENA

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