ECE 53a
Quiz #2 SOLUTIONS
Pamela Cosman
2/11/09
Problem 1:
This is Bobrow problem 2.31, which was assigned to you as part of homework set 3.
The solution set for the homework was already posted.
Problem 2:
(a) This problem was taken directly from quiz 2 from last year. The solution set for that was
already posted too. But I repeat the solution here:
In class, I discussed how to use op amps to scale voltages up and down, including both inverting
and noninverting conFgurations. This problem corresponds to case 4. The conFguration we need
is:
+
V
0


+
V
1

+

+
V
2
10 K
10 K
10 K
(b) Now the ampliFer is no longer an ideal op amp, but rather a Fnitegain ampliFer with gain
A=100.
It is still the case, however, that
V
2
=
V
1
3
where
V
1
is the source voltage, because no current goes
into the input terminals of the op amp, so the left hand side of the circuit is still doing voltage
division.
Now we can write
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 Spring '08
 Cheng
 Thévenin's theorem, isc, ideal op amp, VX VX

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