Name: Daniel Bernard
Team Members: Benjamen Strobel and Jack Ladwig
ECE 2212
Lab #03 Frequency Dependent Operational Amplifier Circuits and Oscillators
Due: February 16, 2012
Lab Coordinator: Stan Burns
Lab TA: Sukriti Subedi
Abstract:
This lab consists of implementation and measurements via circuit designs for the following circuits:
active analog Low-Pass Filter (LPF), active analog High-Pass Filter (HPF), Wien Bridge Oscillator, and a Phase
Shift Oscillator. For the Low-Pass Filter, design and test using the given circuit, values for resistors and the
capacitor that would produce a 20 dB voltage gain with a corner frequency of 3 dB in the 3-5 kHz range. Gain
and Phase shifting should be measured using the oscilloscope, and a transient analysis should be produced via a
PSpice simulation of the circuit, using the same values as what was used to simulate the circuit on a breadboard.
Similar design plans should be implemented on a High-Pass Filter, Wien Bridge Oscillator, and Phase Shift
Oscillator.
Introduction:
This lab covers implementation of active analog Low-Pass Filter (LPF), active analog High-Pass Filter (HPF), Wien Bridge
Oscillator, and a Phase Shift Oscillator. The lab also requires the simulation of the circuits in PSpice, and an applied transient analysis.
Background:
In this lab we apply our knowledge of nodal analysis and voltage division, in addition to our understanding of gain calculations and
phase measurements.
Procedure:
Low-Pass Filter:
Design a low-pass filter using the circuit shown below with a
low-frequency voltage gain of 20 dB, and 3 dB corner
frequency between 3-5 kHz. Simulate and experimentally
verify the circuit.
Measure 20𝑙𝑜𝑔|𝐴(𝑗𝑓)| and 𝜃(𝑗𝑓), and simulate.
High-Pass Filter:
Design a high-pass filter using the circuit shown below with a
high-frequency voltage gain of 20 dB, and 3 dB corner
frequency between 100 Hz-500 Hz. Simulate and
experimentally verify the circuit.
Measure 20𝑙𝑜𝑔|𝐴(𝑗𝑓)| and 𝜃(𝑗𝑓), and simulate.
Wein Bridge Oscillator:
Construct the circuit shown below. Observe the waveform
constructed. Simulate the design in PSpice, and observe the
transient analysis.
Phase Shift Oscillator:
Construct the circuit shown below. Observe the waveform
constructed. Simulate the design in PSpice, and observe the
transient analysis. Compare the frequency of operation to the
equation, 𝑓0 =
1
2𝜋𝑅𝐶√6
, and voltage gain by
Measurements and Analysis of Results:
Low-Pass Filter:
Oscilloscope
𝑅1
𝑅2
Low-
High-Pass Filter:
Wein Bridge Oscillator:
Phase Shift
Oscillator:
> 29.
PSpice
Pass Filter:
𝑉0
𝑉𝑠
=−
𝑅2
𝑅1 (1+𝑗
, 𝑓𝑐 =
𝑓
)
𝑓𝑐
1
2𝜋𝑅2 𝐶
= 4000 𝐻𝑧, 𝑅2 = 3300 Ω, 𝐶 ≅ 1.21 𝑛𝐹, tried 2.5 𝑛𝐹
The Oscilloscope readings and PSpice transient analysis match.
High-Pass Filter:
Oscilloscope
PSpice
𝑅2 = 33000 Ω, 𝐶 = 9.6 − 48 𝑛𝐹, chose 20 𝑛𝐹
Wein Bridge Oscillator:
Oscilloscope
PSpice clipping
PSpice growth
The Oscilloscope and PSpice transient analysis match. Useful at a wide frequency range.
Frequency Input
Output
OP/IP
Phase
20Log10(OP/IP)
(Hz)
(V)
(V)
100
2.1
20.6
9.809524 -179.5
19.83296
500
2.12
20.4
9.622642
-162
19.66589
1000
2.1
18.8
8.952381
-155
19.03877
2000
2.12
15
7.075472
-134
16.99511
5000
2.12
8.2
3.867925
-112
11.74956
Voltage Gain
25
Voltage Gain (dB)
Phase
0
100
20
500
1000
2000
5000
-50
Phase (°)
15
10
5
-100
-150
0
100
500
Frequency (Hz)
1000
2000
5000
Voltage Gain
The Wien Bridge Circuit gives positive gain.
Phase Shift Oscillator:
-200
Frequency (Hz)
Phase
Oscilloscope
PSpice
Effective at low frequency, and inverts the signal.
Frequency Input
Output
OP/IP
Phase
(Hz)
(V)
(V)
100
2.16
1
0.462963 90
20Log10(OP/IP)
500
2.16
4.56
2.111111
105.5
6.490222
1000
2.12
8.5
4.009434
111.1
12.06166
2000
2.2
14.6
6.636364
130
16.4386
5000
2.12
20.2
9.528302
159.7
19.58031
-6.68908
Voltage Gain
150
15
Phase (°)
Voltage Gain (dB)
20
10
5
0
-5
-10
Phase
200
25
100
50
100
500
1000
2000
5000
0
Frequency (Hz)
Voltage Gain
100
500
Frequency
(Hz)
1000
2000
Phase 5000
Summary and Conclusion:
From this lab we constructed circuits that maximized gain at high or low frequencies, and changed gain and phase based on
how far the input frequency was from the corner frequency.