What is crystal oscillator?
A crystal oscillator is an electronic oscillator that uses crystal as a frequency selective element to achieve an inverse piezoelectric effect. It uses the mechanical resonance of the vibrating crystal, which has piezoelectric properties, to obtain an electrical signal with a high-precision frequency. Crystal oscillators are considered superior to ceramic resonators because of their greater stability, higher quality, lower cost, and smaller size.
Crystal oscillators are a prime example of fixed frequency oscillators where accuracy and stability are the most important considerations. They usually use the same circuitry as other oscillators, the only difference being that the crystal replaces the oscillating circuit. With crystal oscillators, the crystal vibrates as a resonator and the resulting frequency determines the vibration frequency. In other words, the crystal acts like a circuit with an inductor, a resistor and a capacitor with a precise resonance frequency. In some cases temperature compensation is used to achieve better thermal stability for the crystal oscillator.
There are many advantages to using crystal oscillators in digital applications. Crystals can be made to have a wide range of specific frequencies. Compared to resonant circuits, crystals have a high Q factor, better temperature stability and much better frequency stability than RC oscillators or LC oscillators. Crystals used in crystal oscillators show very little phase noise.
Crystal oscillators are mainly used in digital integrated circuits to provide a stable clock signal and in special applications that require a high frequency reference.