Electric Circuits
ECSE 2010
Prof. Shayla Sawyer
HW04
Fall 2014
1) Equivalent impedances
L2
1
2
6E-3
A
C1
L1
R2
1
2
2E-7
2E-3
6k
C2
2E-7
B
R1
L3
1
2k
2
3E-3
For the above circuit, determine the impedance between A and B as a single ratio (with s-domain
impedance such as Ls, 1/Cs etc.)
2) Amplifier circuits
U1
+
Vin
R1 V1
Vout
OUT
0
-
1
OPAMP
L1
2
a. For the RL amplifier circuit, determine the relationship between Vout and Vin. As with RC
amplifier circuits, KCL is a good starting point.
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Prof. Shayla Sawyer
HW04
3k
-
uA741
V1
L1
OS2
7
OS1
6
V3
Vout
1
R6
OS1
4k
5
6
1
V2
R5
1k
V-
uA741
-
4
OUT
2
-
5
7
V+
+
OS2
OUT
uA741
2
15.9E-3
3
+
0
2
1
U2
U3
3
1k
1
OS1
R4
V+
6
4
2
4
R1
5
OS2
OUT
V-
+
0
V-
Vin
V+
U1
3
Fall 2014
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Electric Circuits
ECSE 2010
R3
R2
1k
4k
0
b. If Vin=10sin(ωt)V, with a frequency of 2kHz (remember to use radial frequency). Find Vout.
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Electric Circuits
ECSE 2010
Prof. Shayla Sawyer
HW04
Fall 2014
3) Voltage/Current continuity
R1
+ 4k -
+2
L1
10uH
V1
+
-1
-
R2
2k
+
-
R3
2k
In the above circuit, the voltage is defined as follows:
5V
V1 = 
0
t<0
(the voltage source turns off at t = 0)
0<t
a. At t =0- (just before the voltage changes), determine the voltage across each resistor and the current
through each resistor for the polarities indicated in the circuit.
b. At t=0+ (just after the voltage changes), determine the voltage across each component and the current
through each component for the polarities indicated in the circuit.
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Electric Circuits
ECSE 2010
Prof. Shayla Sawyer
HW04
Fall 2014
R4
+
4k
+
V2
-
C1
1n
+
-
+
-
R6
2k
R5
2k
In the above circuit, the voltage is defined as follows:
 5V
V1 = 
10V
t<0
(the voltage source changes from 5V to 10V at t = 0)
0<t
c. At t =0- (just before the voltage changes), determine the voltage across each resistor and the current
through each resistor for the polarities indicated in the circuit.
d. At t=0+ (just after the voltage changes), determine the voltage across each component and the current
through each component for the polarities indicated in the circuit.
TCLOSE = 2E-4
4)
R1
1
U1
5k
V1
C1
2
R2
0
In the above circuit, the voltage source turns on at t = 0, V1 = 20u(t). At t = 2E-4 [s], switch U1
closes. (Only the value of R1 is given but the variables C1 and R2 will be determined below.)
a. Determine C1 such that the voltage across C1 is 2.5 V when the switch closes.
b. Determine R2 such that the steady state (t>>>0) voltage across the capaictor is 7.5V.
c. At what time is the voltage across the capacitor 5V?
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Electric Circuits
ECSE 2010
Prof. Shayla Sawyer
HW04
Fall 2014
5)
2
6k
12k
2
1
U4
1
U2
R1
U3
1
12k
10Vdc
2
1
2
U1
V1
5E-7
6k
3k
In the above circuit, switches U1 and U2 close at t =0, and switches U3 and U4 close at t = 0.5 ms.
a. Determine the voltage across the capacitor as a function ot time.
b. Determine the current across R1 as a function of time.
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Electric Circuits
ECSE 2010
Prof. Shayla Sawyer
HW04
Fall 2014
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Electric Circuits
ECSE 2010
Prof. Shayla Sawyer
HW04
Fall 2014
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