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Types of Oscillators

byee-diary • • 2 min read
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Oscillators are crucial electronic components that generate repetitive signals in the form of waves, commonly used in various applications such as communication systems, timing circuits, sensors, and more. Oscillators play a fundamental role in modern technology, and understanding the different types of oscillators is essential for engineers, hobbyists, and electronics enthusiasts alike. In this blog post, we will explore the basics of oscillators and delve into some of the most commonly used types of oscillators.

Oscillators

Oscillators are electronic circuits that produce a continuous, repetitive waveform output without requiring an external signal. These waveforms can be sinusoidal, square, triangular, or sawtooth, and they have specific frequencies and amplitudes. 

Types of Oscillators

Oscillators can be classified into two main categories:

  1. Harmonic Oscillators
  2. Relaxation Oscillators

1. Harmonic Oscillators

Harmonic oscillators are designed to generate sinusoidal or pure waveforms. These type of oscillator circuits are typically used in applications where a precise and stable frequency is required. Some common types of harmonic oscillators include:

  • RC Oscillators
  • LC Oscillators
  • Crystal Oscillators

  • RC Oscillators

RC oscillators use resistors (R) and capacitors (C) to generate a sinusoidal waveform. They are simple and widely used in low-frequency applications. Examples of RC oscillator include RC phase shift oscillator, Wien bridge oscillator, Twin-T oscillator etc.

  • LC Oscillators

LC oscillators use inductors (L) and capacitors (C) to generate a sinusoidal waveform. These oscillator circuits are commonly used in radio frequency (RF) applications. Bipolar Junction transistor(BJT or Field effect Transistors(FET) can be used for the amplifying part of the LC oscillator. Popular and widely used LC oscillator name include Colpitts oscillator, Hartley oscillator, FET Pierce oscillator,  etc.

An example of BJT transistor Colpitts oscillator build on breadboard is shown below.

colpitts oscillator on breadboard

An example of JFET Colpitts oscillator circuit is shown below.

 Self Biased JFET Colpitts Oscillator circuit diagram

  • Crystal Oscillators

Crystal oscillators use a quartz crystal resonator to generate a highly stable and precise sinusoidal waveform. Crystal oscillator circuit are widely used in applications where high accuracy and stability are critical, such as in digital clocks, microcontrollers, and communication systems. Crystal oscillator circuit can be designed with Colpitts configuration, Hartley oscillator configuration, Pierce oscillator configuration etc. Pierce crystal oscillator or transistor pierce oscillator are used widely popular because it is easy to build and it provides stable oscillation.

2. Relaxation Oscillators

Relaxation oscillators generate non-sinusoidal waveforms, such as square, triangular, or sawtooth waves. They are used in applications where the shape of the waveform is not critical, and a simple and cost-effective solution is required. Some common types of relaxation oscillators include:

  • Astable Multivibrator

Astable multivibrator is a type of relaxation oscillator that produces a continuous square wave output. It uses two transistors or operational amplifiers and a few passive components to generate the waveform. Astable multivibrators are commonly used in applications such as timing circuits, pulse generators, and frequency dividers. Astable multivibrator can be designed using transistors, or IC like 555 Timer astable multivibrator.

  • Schmitt Trigger Oscillator

The Schmitt trigger oscillator is another type of relaxation oscillator that generates a square wave output. It uses a Schmitt trigger, which is a type of comparator with hysteresis, to produce a stable square wave output. Schmitt trigger oscillators are used in applications such as signal conditioning, waveform generation, and noise reduction. Many VCO(Voltage Controlled Oscillator) are designed using schmitt trigger oscillator circuit such as the 555 VCO.

  • Sawtooth Wave Oscillator

Sawtooth wave oscillators generate a sawtooth waveform, which is a linearly increasing voltage followed by a sudden drop to a starting voltage. They are commonly used in applications such as timebase generators, waveform generation, and analog-to-digital converters.

Conclusion

Oscillators are essential electronic components that generate repetitive waveforms for various applications. Understanding the different types of oscillators, including harmonic oscillator circuits such as RC oscillators, LC oscillators(eg  Colpitts and Hartley oscillator, Pierce oscillator) which are commonly used in RF circuit, and crystal oscillators(eg  pierce crystal oscillator), as well as relaxation oscillators such as astable multivibrators, Schmitt trigger oscillators, and sawtooth wave oscillators, is crucial for designing and implementing electronic circuits. Choosing the right type of oscillator for a specific application depends on factors such as the required frequency, waveform shape, stability, and cost. By gaining a solid understanding of the types of oscillators,and their applications, engineers and electronics enthusiasts can make informed decisions when selecting and designing oscillators for their projects.


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