Article catalog

1. What is an oscillator
2. Working principle of oscillator
3. What kinds of oscillators are there
RC oscillator
LC oscillator
Crystal oscillator
Other types of oscillators
4. The main components of the oscillator
5. What are the performance indicators of the oscillator?
6. Application of oscillator
7. How to design or make a simple oscillator
8. Conclusion

Have you ever wondered what an oscillator really is and why it occupies such an important place in the field of electronics?

Whether you are building a radio communication system or designing a complex computer architecture, it is vital to understand the basic principles and applications of oscillators. Oscillators not only play a key role in scientific research and industrial production, they are also an indispensable element of technology in everyday life, from ensuring the synchronous operation of components inside electronic devices to creating beautiful melodies in music synthesizers. In the following sections, INFINITECH will explain the essence of the oscillator, how it works, and how to choose the right type of oscillator for different needs. In this article, you will have a comprehensive understanding of all aspects of the oscillator and be able to determine whether it meets your test or application needs. Let's unravel the mystery of the oscillator.

1. What is an oscillator

An oscillator is an electronic device or circuit that produces periodic electronic signals, usually in a variety of waveforms such as sine, square or triangular waves. Its operating frequency range can be extended from millihertz to gigahertz and beyond. The role of oscillators is very broad. In the field of radio communication, the carrier signal generated by them is the key to information transmission; In computers and other digital systems, oscillators act as clock sources, ensuring synchronous operation between components; In the modulation process, the signal sent by the oscillator is used to change the characteristics of the carrier, so as to realize the data coding; In laboratory Settings, oscillators are often used as test signal sources to help evaluate the performance of other electronic devices; In music synthesizers and instruments, oscillators are responsible for generating basic tones and producing different sound effects through subsequent processing. Therefore, the oscillator is not only an important tool in scientific research and industrial production, but also an indispensable part of daily life entertainment.

In electronics, the importance of the oscillator cannot be ignored. High quality oscillators are essential to ensure signal stability and accuracy, especially in applications where frequency stability is strictly required. In addition, the reliable operation of the oscillator directly affects the normal operation of the entire system, especially in an environment that requires continuous trouble-free operation for a long time. Efficient design can also help reduce energy consumption, which is especially important for portable devices.

2. Working principle of oscillator

The operating principle of an oscillator relies primarily on a positive feedback mechanism, which allows the circuit to spontaneously produce a stable oscillating signal without external signal input. In an oscillator, a portion of the output signal is fed back to the input, and if this feedback is positive (i.e. the same phase), it enhances the original signal, allowing the oscillation to continue. In order to start the oscillating process, the circuit must have sufficient gain to overcome internal losses and, by adjusting the gain, ensure that the oscillating signal is not overloaded. A frequency-selective network in the oscillator (such as an LC resonant loop or a quartz crystal) determines the oscillation frequency, while the Barkhausen criterion specifies the loop gain and phase conditions necessary for the oscillator to start and operate stably, that is, the loop gain must be equal to 1 and the total phase shift must be an integer multiple of 360 degrees (or 2π radians).

The circuit composition of the oscillator consists of several key parts: the amplifier is used to provide the necessary gain, which can be a transistor, an operational amplifier or a field effect tube; The feedback network sends part of the output signal back to the input of the amplifier, and its design determines the frequency characteristics and waveform of the oscillator. Frequency selection network is composed of inductor, capacitor LC circuit or quartz crystal, which is used to select a specific frequency; The bias circuit ensures that the amplifier works in its linear region, avoiding signal distortion; The power supply provides the required DC voltage or current to the oscillator. These components work together to ensure that the oscillator can produce a stable and predetermined frequency signal.

Once the circuit is energized, the initial noise signal is captured and amplified by the amplifier, and then sent back to the amplifier's input via a feedback network. If the Barkhausen criterion is satisfied, these tiny noisy signals are amplified until the oscillator's gain and loss in the feedback path reach an equilibrium point, at which point the output signal reaches a stable state. Although different types of oscillators (such as RC oscillators, LC oscillators, crystal oscillators, etc.) may have different specific implementations, they all follow the above basic principles to achieve self-generation and stability of the signal. This process makes the oscillator an integral part of modern electronic technology.

3. What kinds of oscillators are there

Understand the different types of oscillators to facilitate the design of the system according to the specific application needs to choose the most suitable oscillator type.

Here are some common oscillator types and their characteristics:

RC oscillator

RC oscillators mainly rely on resistance and capacitance components to determine the oscillation frequency. This type of oscillator is simple in structure and low in cost, and is usually used to generate low-frequency signals. The most common type of RC oscillator is the Wien Bridge oscillator, which sets the frequency through an RC network and uses an operational amplifier as the amplification unit. RC oscillators have the advantage of being easy to adjust the frequency, but due to their inherent nonlinear nature, the resulting signal is usually less pure than other types of oscillators.

LC oscillator

LC oscillators use a resonant loop consisting of inductors (L) and capacitors (C) to determine the oscillation frequency. Such oscillators are capable of producing signals at higher frequencies, and because LC resonant loops have a high quality factor (Q value), they can produce a relatively pure sine wave signal. There are several common types of LC oscillators, including Hartley oscillators, Kolpitz oscillators, and Clapper oscillators. The Kolpitz oscillator uses two capacitors in parallel with an inductor, while the Klapper oscillator adds an additional capacitor to improve frequency stability.

Crystal oscillator

Crystal oscillators use the piezoelectric effect of quartz crystals to produce very stable and precise oscillation frequencies. Quartz crystals exhibit resonance characteristics at a specific frequency that is almost unaffected by temperature changes, so crystal oscillators have extremely high frequency stability and accuracy. Crystal oscillators are widely used in applications requiring high stability and high accuracy, such as clocks, timers, communication systems, etc. Crystal oscillators are relatively costly compared to RC and LC oscillators, but are preferred in applications where precise frequency control is required.

Other types of oscillators

Voltage controlled oscillator (VCO) : The frequency of this type of oscillator can be adjusted by a control voltage, and it is widely used in frequency synthesizers and modulators.

Sag oscillator: This type of oscillator usually produces non-sinusoidal waveforms, such as square or triangular waves, and is commonly found in timers and pulse generators.

Digital oscillator: In a digital system, an oscillator that uses a combination of logic gates can generate a clock signal, and this type of oscillator has a wide range of applications in digital electronics.

4. The main components of the oscillator

An oscillator is a circuit made up of several key components, each of which plays an important role in its operation. Understanding these key components and their respective functions helps to better grasp the use of oscillators in practical applications. Below, INFINITECH lists the main components that make up the oscillator and their functions:

amplifier

The amplifier is one of the core components of the oscillator, which is responsible for amplifying the signal in the circuit. The amplifier in the oscillator can be any type of amplification device, such as a transistor (BJT or FET), an operational amplifier (Op-Amp), etc. The amplifier provides the necessary gain to compensate for the loss of the signal in the oscillator loop, ensuring that the signal can be amplified continuously until it reaches a stable state.

Feedback network

The feedback network is the part of the circuit that sends a portion of the oscillator output signal back to the input. The design of the feedback network determines the frequency characteristics and waveform of the oscillator. The feedback can be positive, i.e. the feedback signal is in phase with the input signal, which can enhance the signal and facilitate the establishment of oscillations. The feedback network usually consists of resistance, capacitance, and/or inductor elements whose configuration affects the frequency stability of the oscillator.

Frequency-selective network

A frequency-selective network (also known as a resonant loop or filter network) is used to select the oscillation frequency of an oscillator. In LC oscillators, this network consists of inductors (L) and capacitors (C), which together determine the operating frequency of the oscillator. For crystal oscillators, the frequency-selective network is the quartz crystal itself. Another important role of the frequency selection network is to provide a certain quality factor (Q value), thereby improving the purity of the output signal.

Bias circuit

The bias circuit ensures that the amplifier is in the correct operating condition, especially in analog oscillators, and the bias circuit ensures that the amplifier is able to operate in its linear region, thus avoiding signal distortion. The design of the bias circuit is very important to the stability and efficiency of the oscillator.

Power source

The power supply provides the required DC voltage or current to the oscillator, ensuring that the circuit can work properly. The quality of the power supply directly affects the stability of the oscillator and the quality of the output signal. In some cases, in order to improve the stability of the oscillator, it is also necessary to use a regulated power supply to eliminate the influence of power fluctuations on the oscillator.

Starting circuit

While not all oscillators require a separate starting circuit, some designs may include circuits specifically designed to start the oscillator. The role of the starting circuit is to provide the initial excitation to help the oscillator transition from a stationary state to an oscillating state.

These components cooperate with each other to work together on the working process of the oscillator, so that it can produce a stable and predetermined frequency signal.

5. What are the performance indicators of the oscillator?

The oscillator can be evaluated by the following performance parameters.

Frequency stability

Frequency stability refers to the ability of an oscillator to keep its output frequency constant for a certain amount of time. It is affected by a variety of factors, including temperature changes, power supply voltage fluctuations, load changes, aging and other factors. Frequency stability is usually expressed in ppm (parts per million) or ppb (parts per billion). High-performance oscillators usually have extremely high frequency stability, such as atomic clocks that can achieve very high frequency stability.

Amplitude stability

Amplitude stability refers to how the amplitude of the oscillator output signal changes over time. Ideally, the oscillator should be able to provide a constant amplitude signal output. Amplitude instability may lead to signal distortion and affect the performance of subsequent processing. Amplitude stability can be improved by techniques such as automatic gain control (AGC).

Harmonic distortion

Harmonic distortion means that the oscillator output signal contains frequency components other than the fundamental wave, usually in the form of integer multiples of the fundamental frequency. These harmonic components can cause signal distortion, especially for applications that require pure sine waves, such as communication systems. Harmonic distortion is usually measured in terms of total harmonic distortion (THD), expressed as a percentage relative to the fundamental wave amplitude.

Phase noise

Phase noise is the degree to which the instantaneous phase of the oscillator output signal deviates from its ideal value. It usually occurs in the frequency domain and appears as side band noise near the fundamental wave. Phase noise is particularly important for high frequency applications, such as wireless communications, radar systems, etc. Phase noise can be expressed in terms of dBc/Hz (carrier decibels per Hertz) and is usually measured at a certain offset frequency.

Temperature coefficient

The temperature coefficient reflects the degree to which the oscillator output frequency changes with temperature. For oscillators that need to operate at different ambient temperatures, the temperature coefficient is a key indicator. Low temperature drift (low temperature coefficient) oscillators are ideal for demanding applications.

Starting time

Starting time refers to the time required for the oscillator from power-on to output a stable signal. In some real-time applications, the shorter the start time, the better.

Power dissipation

Power consumption is a measure of the efficiency of an oscillator, especially in battery-powered devices. Low power oscillator can extend the service life of the device.

Frequency range

Frequency range refers to the frequency range that the oscillator can cover. For applications that need to operate over a wide frequency range, such as tunable oscillators, the frequency range is an important parameter.

Modulation capacity

For applications that require modulation, such as frequency modulation (FM) or phase modulation (PM), the ability of the oscillator to modulate is also an important indicator. The modulation capability includes the maximum modulation index, modulation frequency range, etc.

Output impedance

The output impedance determines the match between the oscillator and the load, which in turn affects the signal transmission efficiency. The ideal output impedance should match the load impedance to maximize the transmission power.

6. Application of oscillator

Communication system

In mobile phones, satellite communications, wireless local area network (Wi-Fi) and other systems, oscillators are used to generate carrier signals as carriers of information transmission. The reference frequency provided by the oscillator is used to modulate the information onto the carrier and demodulate the original information at the receiving end. In multi-band communication systems, oscillators are used to generate multiple frequency signals to support different channels or frequency bands.

Radio and television

The oscillator is used in the broadcast station to generate the frequency of the transmitted signal to ensure the stable transmission of the broadcast signal. It is used in television sets to generate synchronization signals to ensure the correct display of images and sound.

Radar and navigation

Oscillators are used in radar systems to generate high frequency signals for target detection and ranging. Provides an accurate time reference in a GPS receiver for calculating position information.

Computer time clock

The oscillator acts as the computer's internal clock source, ensuring time synchronization between the processor and other components. The oscillator is used in the RTC module to provide accurate time, keeping the time accurate even when the device is powered off.

Test and measurement

In the lab, oscillators are used to generate test signals to calibrate and verify the performance of other electronic devices. Oscillators are used in spectrum analyzers to generate scanning signals that help identify and analyze signals of different frequencies.

Medical equipment

Oscillators are used in medical devices to generate reference signals that help doctors monitor electrical signals from a patient's heart. Oscillators are used in ultrasonic devices to generate high-frequency sound waves for imaging and diagnosis.

Audio & Music

In audio devices, oscillators are used to generate audio signals, such as speakers, headphones, etc. Oscillators are used in music synthesizers to generate basic tones, which are then processed to form different sound effects.

aerospace

Oscillators are used in satellite communication systems to generate the frequencies needed to transmit and receive signals. Provide accurate time benchmarks in the navigation systems of aircraft and spacecraft.

Industrial automation

In industrial automation systems, oscillators are used to generate the synchronization signals required by sensor networks; Clock signals are provided in the automated control system to ensure the coordinated operation of all parts of the system.

Education and research

In electronic engineering teaching, oscillators are used as part of experimental equipment to help students understand and learn the principles of electronics. In scientific research, oscillators are used to generate signals of specific frequencies, supporting a variety of physical, chemical, and biological experiments.

7. How to design or make a simple oscillator

Taking the example of making a simple RC (resistance-capacitance) oscillator, the following INFINITECH provides a basic guide to help you understand how to make such an oscillator. Here we will use a common circuit, the Wien bridge oscillator, as an example.

a. First prepare the materials

Operational amplifier (Op-Amp) : For example, LM324 or LM358.

Resistance: 3 10kΩ resistors.

Capacitors: 2 1μF capacitors.

Power supply: ±12V DC power supply or single power supply plus bias circuit.

Breadboard: Used to build circuits.

Wire: Connects circuit elements.

Multimeter: Test circuit.

Oscilloscope (optional) : Observe waveforms.

b. Design steps

Step 1: Understand the circuit principle

The Wien bridge oscillator is a simple sine-wave oscillator based on a positive feedback mechanism. The RC network determines the oscillation frequency, while the operational amplifier provides the necessary gain.

Step 2: Select component values

According to the formula f = 1/2πRC, select the appropriate R and C values to determine the oscillation frequency. For example, a frequency of about 15.9 Hz can be obtained using a 10kΩ resistor and a 1μF capacitor.

Step 3: Build the circuit

RC network: Two 1μF capacitors and a 10kΩ resistor are connected in series, and then two other 10kΩ resistors are connected in parallel at one end of the two capacitors.

Amplifier connection: Connect one end of the RC network to the in-phase input of the op amp and ground the other end. The intermediate point of the RC network is connected to the output of the op amp to form a positive feedback.

Power connection: Power supply to the operational amplifier, if it is a dual power supply, then connected to ±12V; If it is a single power supply, an appropriate bias circuit may need to be added.

Output connection: Connect the output of the op amp to an oscilloscope or speaker in order to observe or hear the output signal.

Step 4: Adjust the gain

The gain is adjusted by adjusting the value of the third 10kΩ resistor (connected between the inverting input and output of the op amp) until the circuit begins to oscillate. The theoretical gain needs to be at least 3 for vibration to start.

Step 5: Test and debug

Use a multimeter to check that the circuit is properly connected and that there is no short circuit.

Connect the power supply, turn on the power switch, and use the oscilloscope to observe the output waveform. If the circuit does not vibrate, check whether the connection is correct and adjust the resistance value appropriately.

If the circuit vibrates, observe whether the waveform is stable and adjust the resistance value to obtain the desired oscillation frequency and waveform quality.

c. Precautions

In the actual production process, it may be necessary to adjust the resistance value several times to achieve the desired oscillation effect.

Make sure all components meet specifications and that the circuits are connected correctly.

Safety first, please follow basic electrical safety rules when operating.

With the above steps, you can build a basic RC oscillator. This is a good introductory project for beginners to learn how oscillators work.

8. Conclusion

Combined with the above, oscillators play a key role in many fields. Whether it is by generating a stable periodic signal to ensure system synchronization, or as a test signal source to evaluate equipment performance, the importance of the oscillator cannot be underestimated. In this article, INFINITECH introduces in detail the working principle of oscillators, the different types and their applications, and discusses the basic methods of designing and making oscillators. By understanding the core components of oscillators and their performance metrics, readers can better select and apply the oscillator that best suits their needs, thereby improving the design efficiency and reliability of electronic systems.