How Oscillator Works ? The Working Principle of the Oscillator Explained

Summary

This video from the 'All About Electronics' YouTube channel delves into the fundamentals of electronic oscillators, exploring their widespread applications in devices like laptops, smartphones, and radios. It explains how oscillators transform DC voltage into AC signals, covering a vast frequency range. The tutorial outlines the critical Barkhausen criteria for sustained oscillations, emphasizing the balance between loop gain and phase shift. It also touches on the role of thermal noise in initiating oscillations without an input signal, and hints at future discussions on various oscillator types like RC, LC, and crystal oscillators.

Takeaways

• 📡 Electronic oscillators are crucial in various applications such as generating clock signals for processors, local carrier frequencies for radio and mobile receivers, and for testing circuits in signal generators.
• 🔌 Oscillators transform DC voltage into periodic AC signals over a broad frequency range, from a few Hz to GHz, and can produce sinusoidal or non-sinusoidal waveforms like square or triangular waves.
• 🔁 The core of an oscillator circuit is an amplifier with positive feedback, where the output signal is a product of the input signal and the amplifier's gain.
• 🔄 Feedback circuits in oscillators are typically frequency selective or resonant, ensuring that only specific frequencies are reinforced and sustained.
• 🔄 The feedback fraction (β) determines the portion of the output voltage that is fed back to the input stage, influencing the loop gain of the oscillator.
• 🔄 Sustained oscillations occur when the loop gain (product of amplifier gain 'A' and feedback fraction 'β') equals 1, and the phase shift introduced by the amplifier and feedback circuit is zero, known as Barkhausen's criteria.
• 🔄 Oscillators can initiate oscillations from thermal noise present in circuits due to their initial loop gain set slightly above 1, which allows a specific frequency component to build up over time.
• 🔍 The feedback circuits can be made of RL, RC, or RLC components, or even quartz crystals, classifying oscillators into different types such as RC, LC, or crystal oscillators.
• 🛠 Relaxation oscillators, which produce non-sinusoidal waveforms like square or triangular waves, can be constructed using op-amps or timer ICs like the 555 timer.
• 📚 The script promises future videos that will delve into the design of various types of oscillators, providing a deeper understanding of their applications and configurations.

Q & A

What are electronic oscillators used for?

Electronic oscillators are used in a wide range of applications including generating clock signals for laptop and smartphone processors, generating local carrier frequencies in radio and mobile receivers, and in signal generators used in labs to test circuits.

What is the frequency range of electronic oscillators?

Electronic oscillators can generate frequencies from a few Hz to even GHz.

What types of signals can oscillators produce?

Oscillators can produce sinusoidal signals or non-sinusoidal signals like square waves and triangular waves.

What is the basic concept behind an oscillator circuit?

An oscillator circuit is essentially an amplifier with positive feedback.

What is the role of the feedback circuit in an oscillator?

The feedback circuit in an oscillator is typically a frequency selective or resonant circuit that determines the fraction of the output voltage that is fed back to the input stage.

What is meant by the loop gain of an oscillator?

The loop gain of an oscillator is the product of the amplifier's gain (A) and the feedback fraction (β), which determines whether sustained oscillations can occur.

What are the Barkhausen's criteria for sustained oscillations?

The Barkhausen's criteria for sustained oscillations are that the product of the amplifier's gain (A) and the feedback fraction (β) should be equal to 1, and the overall phase shift introduced by the amplifier and feedback circuit should be zero.

How do oscillators start oscillating without an initial input signal?

Oscillators start oscillating due to the thermal noise present in every circuit, which contains all frequency components. The loop gain is initially set slightly greater than 1, allowing a particular frequency component to build up over time until sustained oscillations occur.

How can the two criteria for sustained oscillations be mathematically proven?

The two criteria for sustained oscillations can be mathematically proven by showing that the magnitude of the loop gain should be equal to 1 and the phase shift introduced by the loop gain should be equal to 0.

What are the different types of feedback circuits used in oscillators?

Feedback circuits in oscillators can be made up of RL (resistor-inductor), RC (resistor-capacitor), or RLC (resistor-inductor-capacitor) components, or even quartz crystals for frequency selection.

What is the difference between sinusoidal and relaxation oscillators?

Sinusoidal oscillators, also known as harmonic oscillators, produce sine wave outputs. In contrast, relaxation oscillators produce non-sinusoidal waveforms like square waves or triangular waves and can be built using op-amps or timer ICs like the 555 timer.