MAPÚA UNIVERSITY
School of Electrical, Electronics and
Computer Engineering
Intramuros, Manila
VARIABLE FREQUENCY SINE
WAVE OSCILLATOR
Project Documentation
Submitted by:
MALIBAN, Irish Joy N.
Submitted to:
Engr. Ramon G. Garcia
Professor
TABLE OF CONTENTS
1. Acknowledgment letter
2. Objective
3. Schematic Diagram
4. Cost of Materials
5. Circuit Description
6. References
Engr. Ramon G. Garcia
School of Electrical, Electronics, and Computer Engineering (EECE)
Mapúa University
July 2, 2019
Dear Engr. Garcia:
In compliance with the fulfillment of the requirements on the course Electronics 3 Laboratory,
the group would like to present the prototype and documentation of Variable Sine Wave
Oscillator. This prototype is the product of learning the knowledge attained in electronics III.
The purpose of this project and documentation is to present the prototype Variable Sine Wave
Oscillator that can produce a sine wave with varying frequency. The goal of this project is to
have a bandwidth not smaller than 50kHz and a 1V pk-pk minimum. This prototype is composed
of different electronic components which are discussed in this course as well as previous ones,
such as operational amplifiers, diodes, capacitors, etc. Basically, this prototype is an application
of what we have learned throughout this course.
After the presentation of the project, we would be giving all the rights of this prototype to Mapúa
University, specifically, the school of EECE. We hope that you would find the prototype and the
documentation satisfactory.
Respectfully yours,
_____________________
Maliban, Irish Joy N.
OBJECTIVES
To create a documentation of the said project and be able to present project and defend
the said project.
To apply the knowledge won and acquired from the experiments done from the
laboratory and the principles mentioned from lectures in producing a variable frequency
sine wave oscillator
To create/design a variable frequency sine wave oscillator circuit having a bandwidth not
smaller than 50 kHz and a 1V pk-pk minimum and apply to a PCB.
To build a variable frequency sine wave oscillator with the use of the conventional way
of construction with inclusion of the following component: OP AMPs, resistors,
potentiometer, capacitors, etc.
SCHEMATIC DIAGRAM
MAIN SCHEMATIC DIAGRAM
PRINTED CIRCUIT BOARD
COST OF MATERIALS
1 bottle Ferric Free from Chem dept.
1 pc PCB 150
- Components (5.6k, 8.2k, 2k 96
resistors, 1N4001 diodes,
10nF capacitors, 20k
dualpote, Lf353 IC, 8pin IC
holder)
- Cable wires Recycled
1 Tupperware Recycled
2 9V Batter with battery clips 68
1 Acetate 12
TOTAL ₱326
CIRCUIT DESCRIPTION
An oscillator is an electronic or mechanical device that produces a periodic, oscillating electronic
signal, often a sine wave or a square wave. Oscillators convert direct current (DC) from a power
supply to an alternating current (AC) signal. They are widely used in many electronic devices.
Common examples of signals generated by oscillators include signals broadcast by radio and
television transmitters, clock signals that regulate computers and quartz clocks, and the sounds
produced by electronic beepers and video games.
The electronic oscillator can be regarded as an amplifier, which provides its own input signal. It
is an amplifier circuit, which uses a positive or regenerative feedback where in a part of the
output signal is sent back to the input. Oscillators can be classified into two broad categories
according to their output waveform. These are the Sinusoidal waveform or Harmonic Oscillators
and Non-sinusoidal waveform or Relaxation Oscillators. This paper would focus on Sinusoidal
or Harmonic Oscillators since this documentation features a variable frequency sine wave
oscillator.
The Wien bridge oscillator is an electronic oscillator that produces sine waves. It is a two stage
RC circuit amplifier circuit and it has high quality of resonant frequency, low distortion, and in
the tuning. Consider the very simple sine wave oscillator used by the RC circuit and place in the
conventional LC circuit, construct the output of sinusoidal waveform is called as a Wien bridge
oscillator. The Wien Bridge Oscillator is so called because the circuit is based on a frequency-
selective form of the Wheatstone bridge circuit.
The Wien Bridge Oscillator uses a feedback circuit consisting of a series RC circuit connected
with a parallel RC, basically a high pass filter connected to a low pass filter producing a very
selective second-order frequency dependent band pass filter, of the same component values
producing a phase delay or phase advance circuit depending upon the frequency. At the resonant
frequency ƒr the phase shift is 0.
The variable frequency sine wave oscillator circuit consists of one IC, one dual gauge
potentiometer, three resistor (5.6, 8.2, and 2 kilo ohms) and two pieces of 1nF capacitor. The
frequency bandwidth depends on the value of the capacitances. The circuit has a miller
capacitance effect that is being controlled by the potentiometer. A miller capacitance effect is a
special case of the Miller theorem when the impedance element is a capacitor.
REFERENCES
Electronics 3 Laboratory Manual
https://www.sciencedirect.com/science/article/pii/B978185617505000
0193
https://www.ti.com/lit/an/sloa060/sloa060.pdf
https://www.electronics-
notes.com/articles/analogue_circuits/operational-amplifier-op-
amp/wien-bridge-sine-wave-oscillator-generator.php
https://www.ti.com/sc/docs/apps/msp/journal/aug2000/aug_07.pdf
http://www.learnabout-electronics.org/Oscillators/osc30.php
http://www.ti.com/lit/ds/symlink/lf353.pdf
http://www.differencebetween.info/difference-between-bandwidth-
and-frequency
