LabinaBox
Experiment 17: An Integrator Circuit
Name: ______________________
Pledge: _____________________
ID:
______________________
Date: ______________________
Procedure
Analysis:
1.
Derive the inputtooutput relationship of the amplifier circuit shown in Figure 1 as given in Eq (1).
Which trim pot is required to have a unity gain over the desired operating frequency of 500 Hz to
3000 Hz? Note that the output of the circuit is negative. If a positive sawtooth is desired, you may use
a unity gain op amp inverter circuit following the output of the integrator.
O
U
T
1
+
3

2
V
+
4
V

1
1
U
1
A
L
F
3
5
6
R
3
1
0
k
C
1
0
. 1
u
0
0
0
3
1
2
R
1
V
1
T D
= 0
T F
=
1
n
s
P
W
=
1
m
s
P
E
R
= 2
m
s
V
1
=
1
T R
= 1
n
s
V
2
=
 1
Figure 1: An ideal integrating op amp circuit.
2.
Select the values of the components required such that the integrator
circuit of Figure 2 will have a
gain of unity at 1500 Hz. Determine the values of
R
1
,
R
2
, and
R
4
based on the information provided in
the Background.
R
1
should be a trim pot, or a combination of a trim pot and a fixed resistor with
sufficient range to allow the frequency of the output pulse train be varied from 500 Hz to 3000 Hz
and still maintain unity gain at the operating frequency.
†
Use a 0.1 μF capacitor for
C
1
. Round your
remaining component values to the nearest components available in your kit (see Appendix A).
†
See footnote on page 145 of the text.
1 of 4
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Figure 2: A practical op amp integrator circuit.
Modeling:
3.
Using the component values determined in step 1, model the circuit of Figure 1 in PSpice. Use a
bipolar
±
1.0 V amplitude pulse train as the input signal with frequencies (f) varying from 500 to
3000 Hz in steps of 500 Hz. For each frequency, adjust the value of
R
1
to obtain an output signal of
amplitude 1.0 V. Tabulate the values of R
1
for each frequency. Hint: instructions for sweeping a trim
pot in PSpice may be found on the book WWW site at
http://www.wiley.com/college/Hendricks.
4.
Using your choice of a scientific graphing program (e.g., Excel or MATLAB), plot a graph (in log
log space) of the value of
R
1
versus f. Do not plot data points, but only plot a line joining the data
points. Save your graph for use in step 17.
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 Fall '07
 LKPendleton
 Amplifier, Operational Amplifier, Pspice, trim pot

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