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Comprehensive Introduction of Oscillator Basics

The author perfected this article on January, 7, 2020


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Basics of Oscillators 

An oscillator is an energy conversion device that converts DC power into AC power with a certain frequency. Its circuit is called an oscillating circuit. The oscillator can be divided into two main types: harmonic oscillator and relaxation oscillator. This article will mainly introduce oscillators.


I Introduction

II The Most basic Component of the Oscillator

III Classification of Oscillator

1. RC oscillator

2. LC oscillator

3. Crystal oscillator

4. Temperature coefficient oscillator

5. Temperature compensated crystal oscillator(TCXO)

IV Relevant Technical Term of Oscillator

V Working Principle

VI Usage Process

VII Matters Need Attention

VIII Status of Development

IX Book Suggestion

I Introduction

An oscillator is an electronic component that used to generate repetitive electronic signals (usually sine wave or square wave). Its circuit is called oscillating circuits. They are electronic circuits or devices capable of converting DC to AC signals with a certain frequency. According to the oscillation excitation mode, oscillators can be divided into self-excited oscillator and driven oscillator. According to the circuit structure they can be divided into resistance-capacitance oscillator, LC oscillator, crystal oscillator, fork oscillator and so on; According to the output waveform they can be divided into sine wave, square wave, sawtooth wave and other oscillators. Widely used in electronic industry, medical treatment, scientific research and so on.

Circuits of Self-excited Oscillators

An oscillator is simply a frequency source, typically used in a phase-locked loop. In detail, it is a device that converts DC power into AC power without external signal excitation. It is generally divided into positive feedback and negative resistance type. The so-called "oscillation" means an alternating current, and the oscillator contains a process and function of oscillating.

II The Most basic Component of the Oscillator

1. triode amplifier(for energy control)

2. positive feedback network (feedback part of the output signal to the input end)

3. frequency selection network ; ( to select the desired oscillation frequency so that the oscillator can oscillate at a single frequency to obtain the desired waveform )


r/min or r/m

III Classification of Oscillators

The oscillator is mainly divided into RC/LC oscillator and crystal oscillator.

1. RC Oscillator

RC oscillator

RC Oscillator

An oscillator using an RC network as the frequency-selecting phase-shifting network is commonly referred to an RC sine wave oscillator , which belongs to an audio frequency oscillator .

2. LC Oscillator


A positive feedback oscillator using LC oscillating loop as phase-shifting and frequency-selective network is called LC oscillator.

Classification of LC oscillator:

1) Transformer coupling: Single-tube LC sine wave oscillator, Differential pair LC sine wave oscillator

2) Three point type: Capacitive three-point(colpitts) oscillator, Inductive three-point (Hartley) oscillator

3) Improved three-point type: Clapp oscillator, Seiler oscillator

4) Differential pair oscillator

3. Crystal Oscillator



1) Stable physical and chemical properties.

2) There are positive piezoelectric effect and inverse piezoelectric effect, the resonant frequency of quartz crystal is ωs.

a. When ω=ωs, the piezoelectric effect is strongest, and ωs is called fundamental frequency.

b. When ω=nωs, the piezoelectric effect is also stronger, and ωs is called overtone frequency.

4. Temperature Coefficient Oscillator

The temperature coefficient oscillator is a kind of oscillator. Its oscillating frequency has a specific relationship with temperature, that is, different temperatures correspond to different oscillation frequencies. Otherwise, once the output value of the oscillator is measured, the temperature value can be measured.

1) High temperature coefficient oscillator: its oscillating frequency is greatly influenced by temperature. If the temperature changes slightly, the frequency will change a lot, that is, it is sensitive to temperature and is used for temperature sensor.

2) Low temperature coefficient oscillator: its oscillation frequency is very little affected by temperature, even if the temperature changes greatly, its frequency is basically unchanged

5.Temperature Compensated Crystal Oscillator(TCXO)



TCXO is a kind of quartz crystal oscillator which can reduce the oscillation frequency change caused by the ambient temperature change through the additional temperature compensation circuit.

In TCXO, there are two kinds of temperature compensation methods for frequency temperature drift of quartz crystal oscillator: direct compensation and indirect compensation:

1) Direct Compensation

Direct compensated TCXO is a temperature compensation circuit composed of thermistors and resistive capacitors, which is connected in series with quartz crystal oscillators in the oscillator. When temperature changes, the resistance of the thermistor and the capacitance of the equivalent series capacitance of the crystal vary accordingly. With the simple circuit, low cost, it is suitable for small and low voltage and current situations. However, when the precision of crystal oscillator is less than ±1pmm, direct compensation is not appropriate.

Simple Schematic of Temperature Compensation Circuit

2) Indirect Compensation

Indirect compensation is divided into analog and digital. Analog indirect temperature compensation is composed of thermistor and other temperature sensing elements to form a temperature-voltage conversion circuit. The voltage is applied to a variable-volume diode connected with the crystal oscillator, and the nonlinear frequency drift of the crystal oscillator is compensated by the variation of the series capacitance of the crystal oscillator, which can achieve a high precision of ±0.5 ppm. Digital indirect temperature compensation is added to the analog compensation circuit after the temperature-voltage conversion circuit, and then the first stage A/D converter is added to the digital indirect temperature compensation circuit. This method can realize automatic temperature compensation, which makes the frequency stability of crystal oscillator very high, but the specific compensation circuit is more complex and the cost is higher. It is only applicable to base stations and radio stations and other high-precision cases.

IV Relevant Technical Term of Oscillator


Hartley oscillator


Gunn oscillator


Pierce oscillator


Wien bridge oscillator


clock oscillator


collector tuning oscillator


crystal-controlled oscillator


dielectric resonator oscillator (DRO)


numerically controlled oscillator (NCO)


oscillator, voltage controlled (VCO)


oscillator, relaxation


oscillator, phase shift


oscillator, crystal


oscillator, collector tuning


oscillator, clock




relaxation oscillator


voltage-controlled crystal oscillator (VCXO)


voltage controlled oscillator (VCO)


Variable Crystal Oscillator

V Working Principle

There are mainly LC circuits composed of capacitors and inductors. In order to maintain the oscillation, there must be an amplifier circuit with positive feedback, the LC oscillator is divided into transformer coupling oscillator and three-point oscillator. Since the device is not likely to be completely consistent , the state of the two transistors in the instant of power-up is changed , and the change is more and more intense due to the effect of positive feedback , then leading to a transient steady state. In this way, oscillations are formed from time to time.

How It Works│LC Oscillator Circuit Animation Tutorial

VI Usage Process

1. Put it into the test bottle and keep balance. If it is dual function model, then setting the mode of oscillation.

2. Switch the power on, set the time according to the scale of the machine surface calibration, and adjust the timer to the "normally open" position if it needs to work for a long time.

3. Turn on the power switch and set constant temperature

1) Place the control switch in the "set" section, The temperature displayed on the display screen is the set temperature in this section. Then adjust the knob, set to the temperature you need to work. (The working temperature you set should be higher than the ambient temperature, when the machine starts heating, the yellow indicator light will be on, otherwise the machine won't work)

2) Place the control section switch on the " measuring " end. At the end of "measurement", the temperature displayed on the display screen is the actual temperature of the air in the test box. And with the change of the temperature in the box, the displayed number will change accordingly.

3) When the heat reaches the desired temperature, the heating will automatically stop and the green light will turn on; when the heat in the test box is emitted below the temperature you set, a new round of heating will begin again.

4. Open the oscillating device:

1) Turn on the oscillating switch on the control panel and the indicator light will turn on.

2) Adjust the oscillation speed knob to the desired oscillation frequency.

5. Cut off the power supply after working, set the speed control knob and the temperature control knob to the lowest point.

6. clean the machine and keep it clean.

VII Matters Need Attention

1. The appliance should be placed on the surface of the working table. The environment should be clean and tidy and well ventilated.

2. The power outlet provided by the user should have good grounding measures.

3. It is strictly forbidden to move the machine while it is working normally.

4. No objects are allowed to hit the machine.

5. Children are forbidden to approach the machine to prevent accidents.

6. Make sure the power is off before replacing the fuse.

7. After use, please clean the machine, No water droplets and dirt residue.

VIII Status of Development


Japan's Kingstone, Nibon Dempa Kogyo Corporation founded in 1948 and MOTO from the United States, Sunny-Emi from South Korea and other companies are large producers of quartz crystal devices. Companies that produces quartz crystal oscillators in China: The 10th Research Institute of the Ministry of Electronic Industry, Beijing 707 factory, 875 state-owned plant and some joint ventures, etc. The research and development of synthetic quartz crystals and their components in China started early, and the production capacity was also relatively large. As far as quartz crystal oscillators are concerned, there are still gaps in such aspects as miniaturization, high frequenc and frequency degree characteristics compared with foreign advanced levels. It is the only way to improve the competitiveness in the international market to narrow these gaps as soon as possible, further expand the scale of production and improve the ratio of product performance to price.At the same time, the new development trend of the device, such as the research and application of the oscillator should be also followed.

IX Book Suggestion

1. Theory of Oscillators (Dover Books on Electrical Engineering)

Widely considered one of the classic books on nonlinear oscillators, this comprehensive volume offers a uniquely detailed and thorough discussion of an important branch of mathematics. Indeed, for mathematicians seeking the physical foundations of the theory of nonlinear oscillations, it is a veritable encyclopedia.

Translated from the Russian by F. Immirzi, this edition is especially faithful to the flavor and detail of the original works; the translation has been further edited and abridged by Professor W. Fishwick for maximum clarity and usefulness. In addition, there are many practical examples of the most detailed use of the theory, and although the many electrical circuits investigated use thermionic vacuum tubes rather than transistors, the methods demonstrated are applicable to all similar types of equations.

Ideal as a reference work for engineers and mathematicians with a strong interest in applications, this book will help professionals in the field become aware of the ways in which the phenomena they study can be physically realized or approximated. Abundant references, a full chapter devoted to commentary on more recent works, and an appendix outlining basic theorems of the theory of differential equations round out this comprehensive and important work.

--A. A. Andronov  (Author),‎ A. A. Vitt (Author),‎ S. E. Khaikin (Author)

2. Oscillators Simplified With 61 Projects

Introduction: "One of the most basic of all electronic circuits is the oscillator, or signal generator. Virtually all electronics systems incorporate at least one such circuit. While information on signal generators is not terribly hard to find, there has been no single source devoted to the oscillator until now. This book tells you all you need to know about oscillator and signal generator circuits for almost any application. Over 60 practical projects are included. These circuits can be readily adapted to suit your individual requirements."

--Delton T. Horn  (Author)

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