## What is a Crystal Oscillator or Clock Oscillator?

Crystal Oscillator is an electronic circuit built with crystal elements to generate an electrical or electronic pulse or clock signal. As the oscillator circuit is built with a crystal element it is called a crystal oscillator. The crystal oscillator is also known as a Clock Oscillator as it provides a clock signal for digital electronic integrated circuits.

The crystal oscillators are available in the market with their frequency rating in hertz. Generally, the quartz oscillator is available from a few tens of kilohertz to hundreds of megahertz. Different frequencies are used for different applications. They are also classified into different voltages such as 1.8V, 2.5V, or 3.3V. The characteristics of a good oscillator are low power consumption and low noise because they can be used in very compact devices.

## How does a Crystal Oscillator Work?

Crystal oscillator has a piezoelectric crystal as a frequency selective element. Quartz crystal is the most common type of piezoelectric resonator widely used. So an electric voltage is applied to this piezoelectric material. When the voltage is applied to it the shape of the piezoelectric material changes. When the voltage is removed, the piezoelectric object automatically changes its shape to its original size, and during this time it generates an electrical voltage. As the shape of the piezoelectric object changes its shape or oscillates at a stable resonant frequency, so it can generate a stable clock signal.
So, the crystal oscillator sustains an oscillation by applying and receiving voltage from the piezoelectric resonator.

Also, you will notice that the crystal oscillator is always connected with a single or double capacitor. The two capacitors connected with the crystal oscillator are - 1. Series resonance and 2. Parallel Resonance. At the series resonance, the impedance between two pins of the crystal oscillator is zero while at the parallel resonance, the impedance between two pins is almost infinity. The parallel capacitance is also called load capacitance. The parallel resonance frequency depends on how much parallel capacitance is connected in parallel with the crystal. On the other hand, the series resonance frequency does not depend upon the load capacitance or parallel capacitance. In a common oscillator connection, there a capacitor is connected at both ends of the crystal to the ground.

## The function of Crystal Oscillator

The main function of a crystal oscillator is to generate the oscillating signal. Crystal oscillator provides different modes of oscillation such as fundamental modes, overtone modes, etc. Generally, the high-frequency crystal oscillators provide oscillation with third, fifth, and seventh overtones. Fundamental crystal oscillators are more efficient than overtone oscillators. The construction is also very simple as that.

## Crystal Oscillator Use and Applications

1. You will see the use of crystal oscillators in consumer electronic devices and gadgets such as radio, Television, computers, wristwatches, etc.

2. Crystal oscillators are used in digital electronic processors such as microprocessors, microcontrollers, etc.

3. Crystal oscillators are used in telecommunication circuits such as radio transmitters or radio receivers to stabilize the frequency.

4. Crystal oscillators are used in different automation devices such as RTU(Remote Terminal Unit), MCU(Machine Control Unit), etc.