1. CTU: EE 415 – Advanced Electronics: Lab 2: Oscillators 1
Colorado Technical University
EE 415 – Advanced Electronics
Lab 2: Oscillators
August 2010
Loren K. Schwappach
ABSTRACT: This lab report was completed as a course requirement to obtain full course credit in EE415,
Advanced Electronics at Colorado Technical University. This report introduces two resonating oscillators built using three
resistors, a capacitor, and an Op-Amp.
If you have any questions or concerns in regards to this laboratory assignment, this laboratory report, the process
used in designing the indicated circuitry, or the final conclusions and recommendations derived, please send an email to
LSchwappach@yahoo.com.
I. INTRODUCTION i. CALCULATIONS:
Schmitt Trigger Circuit:
Operational amplifiers (Op-Amps) in feedback
circuitry can be utilized for advanced signal conditioning as
well as linear amplification. Their performance is generally
locked upon their frequency linearity and feedback design.
An oscillator utilizes positive feedback and a triggering to
produce a square wave output.
Oscillator Circuit:
II. OBJECTIVES
This lab uses an operational amplifier (Op-Amp) to
design and build two oscillators. The first Op-Amp resonates
at 200 Hertz and the second resonates at 25k Hertz.
III. DESIGN APPROACHES/TRADE-OFFS ii. EQUIPMENT:
In order to simplify the design of each oscillator To effectively reproduce the circuits built in this lab
hand calculations were simplified by ensuring the values of you will require the following components/parts/software.
each resistor were identical (R1=R2=R3=Rx).
 +/- 5 Volts Direct Current (VDC) Power Source
IV. PROCEDURES / RESULTS  Signal Generator
 Breadboard
 Three (3) 2.365M Ohm Resistors
This section outlines the procedures required to
reproduce this lab and obtain similar results.  741 Op-Amp
 Multisim Version 11, by National Instruments
A. PART 1 – 200 HZ OSCILLATOR  Oscilloscope
To design the 200 Hz oscillator using a 1n Farad
capacitor, a resistance value of 2.275M ohms was calculated
using equation (6). After verifying the output frequency with
Multisim this resistance value was increased to 2.365M ohms
producing a better frequency result.

2. CTU: EE 415 – Advanced Electronics: Lab 2: Oscillators 2
iii. CIRCUIT DIAGRAM: From Figure 2 it is observed the 200 Hertz oscillator
correctly produced the 200 Hertz square wave. This was
further verified by the oscilloscope.
Figure 3: Oscilloscope results of 200 Hertz oscillator circuit.
.
B. PART 2 – 25 KHZ OSCILLATOR
After recalculating the resistor values using equation
(6) a value of 18.2k Hertz was chosen. However, after
simulating the circuit in Multisim it was discovered that a
resistor value of 5.5k ohms produced a frequency very close
to 25k Hertz. However, due to the slow switching speed of
the 741 Op-Amp, due to its parasitic resistance and
capacitance, the output waveform appeared more like a
triangle wave than a square wave. Thus the 25k Hz Op-Amp
design performed very poorly as an oscillator circuit.
i. CALCULATIONS:
The equations for the 25k Hertz oscillator were the same as
Figure 1: Multisim design of 200 Hertz oscillator. the 200 Hertz oscillator.
Schmitt Trigger Circuit:
iv. RESULTS:
Oscillator Circuit:
Figure 2: Multisim transient analysis results of 200 Hertz
oscillator.

3. CTU: EE 415 – Advanced Electronics: Lab 2: Oscillators 3
ii. EQUIPMENT: iv. RESULTS:
 +/- 5 Volts Direct Current (VDC) Power Source
 Signal Generator
 Breadboard
 Three (3) 5.5k Ohm Resistors
 741 Op-Amp
 Multisim Version 11, by National Instruments
 Oscilloscope
iii. CIRCUIT DIAGRAM:
Figure 5: Multisim transient analysis results of 25k Hertz
oscillator.
From Figure 5 it is observed the 25k Hertz oscillator
produced a 25k Hertz signal, however as a square wave the
signal was very distorted demonstrating the slow frequency
response of the oscillator due to parasitic resistance and
capacitance. This was further verified by the oscilloscope.
Figure 6: Oscilloscope results of 25k Hertz oscillator circuit.
C. PART 3 –200 HZ WORST CASE (-20%R AND +20%R)
The next stage in the lab was to verify the worst case
behavior of oscillator with resistors lower (-20%) than the
calculated value, and with resistors higher (+20%) than the
Figure 4: Multisim design of 25k Hertz oscillator.
calculated value. The 200 Hertz oscillator resistance value of
2.28M ohms was used as the base resistance. Using this
values for the worst high and low case were obtained.
i. CALCULATIONS:

4. CTU: EE 415 – Advanced Electronics: Lab 2: Oscillators 4
ii. EQUIPMENT:
 +/- 5 Volts Direct Current (VDC) Power Source
 Signal Generator
 Breadboard
 Three (3) 1.82M Ohm Resistors
 Three (3) 2.73M Ohm Resistors
 741 Op-Amp
 Multisim Version 11, by National Instruments
 Oscilloscope
iii. CIRCUIT DIAGRAM:
Figure 3: Multisim design of 200 Hertz oscillator, Worst case
scenario, high resistance, +20%.
iv. RESULTS:
The worst case low scenario produced a 164 Hertz
oscillating signal, while the worst case high scenario produced
a 175 Hertz signal. The calculated resistance produced a 169
Hertz signal.
Figure 2: Multisim design of 200 Hertz oscillator, Worst case
scenario, low resistance, -20%.

5. CTU: EE 415 – Advanced Electronics: Lab 2: Oscillators 5
Figure 7: Oscilloscope results of 200 Hertz oscillator circuit
displaying worst case high results.
V. CONCLUSIONS
Figure 4: Multisim transient analysis of 200Hz worst case The Op-Amp oscillator circuit utilized a hysteresis
low circuit. loop to create oscillation from the positive feedback of a
Schmitt trigger. This coupled with slow negative feedback
created oscillation. Conditions for oscillation include a
charged storage device (capacitor/inductor) and a resistor to
control the oscillation frequency.
REFERENCES
[1] Neamen, D. A., “Microelectronics Circuit Analysis and
rd
Design 3 Edition” John Wiley & Sons, University of New
Mexico, 2007.
Figure 5: Multisim transient analysis of 200Hz worst case
high circuit.
Figure 6: Oscilloscope results of 200 Hertz oscillator circuit
displaying worst case low results.
.