EECS
314
Winter 2009
Homework set ___
Student’s name ___________________________
Discussion section # _______
(Last, First, write legibly, use ink)
(use ink)
Instructor is
not responsible
for grading and entering scores for HW papers lacking clear
information in the required fields above
Scores for the HW set:
Problem
1
2
3
4
5
6
7
Total
Score
Problem 1 The “Golden Rules” applied to a basic Op Amp circuit
For the circuit shown on the diagram,
do the following:
Part 1 (10 points)
Write the node voltage equation for
V
+
, first without using the GR and
then after applying the GR, in the
space below.
Part
1
2
3
4
Total
Without using Golden Rules, apply KCL at the V
+
node.
Summing currents leaving the node:
10mA + (V
+
 0) / 200 + I+ = 0
=> 10mA + V
+
/ 200 + I+ = 0
Now, apply Golden Rule (zero current entering input nodes of opamps).
10mA + V
+
/ 200 + 0 = 0
=> 10mA + V
+
/ 200 = 0
From the latter equation, calculate the voltage
V
+
in volts and write your answer:
V
+
= __2___ V
V
+
/ 200 = 10 mA => V
+
= 10 mA * 200
Ω
= 2V
© 2008 Alexander Ganago
Page 1 of 1
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
EECS
314
Winter 2009
Homework set ___
Student’s name ___________________________
Discussion section # _______
(Last, First, write legibly, use ink)
(use ink)
Instructor is
not responsible
for grading and entering scores for HW papers lacking clear
information in the required fields above
Problem 1, continued
The ckt diagram is repeated here for your convenience.
Part 2 (10 points)
Write the node voltage equation for
V
–
, first
without using the GR and then after applying
the GR, in the space below.
Without using Golden Rules, apply KCL at the V

node.
Summing currents leaving the node:
I
10
+ I
50
+ I = 0
=> (V

 (4))/10k + (V

 V
OUT
)/50k + I = 0
Now, apply Golden Rules (zero current entering input nodes of opamps, V
+
= V

).
(2 + 4)/10k + (2  V
OUT
)/50k + 0 = 0
=> 2/10k + (2  V
OUT
)/50k = 0
From the latter equation, calculate the voltage
V
OUT
in volts and write your answer:
V
OUT
= __8____ V
2 /10k  2/50k = V
OUT
/50k => V
OUT
= 10  2 = 8 V
© 2008 Alexander Ganago
Page 2 of 2
EECS
314
Winter 2009
Homework set ___
Student’s name ___________________________
Discussion section # _______
(Last, First, write legibly, use ink)
(use ink)
Instructor is
not responsible
for grading and entering scores for HW papers lacking clear
information in the required fields above
© 2008 Alexander Ganago
Page 3 of 3
Part 3 (10 points)
From the the node voltages, calculate the currents
I
10
,
I
50
, and
I
91
in mA and write
your answers:
I
10
= __.2____ mA
I
50
= __.2____ mA
I
91
= __87.9 mA
Part 4 (10 points)
From KCL, calculate the Op Amp's output current
I
OUT
in mA and write your answer:
I
OUT
= ___88.1___ mA
I
OUT
= I
91
+ (I
50
) = 87.9 mA + .2mA = 88.1 mA
Verify whether KCL is valid at the ground node. Write your conclusion:
Yes / No
(circle one)
Do not be surprised by the possible “violation” of KCL: your calculation is
incomplete, because the circuit diagram is incomplete, lacking the power supplies
(such as – 12 V and +12 V), which can carry large currents!
Show your work.
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document