kristaloscillator

A kristaloscillator is an electronic oscillator that uses a piezoelectric crystal, most commonly quartz, as its frequency-determining element. The crystal's mechanical resonance provides a highly stable reference signal used to generate clock signals for digital systems and communication equipment.

Principle of operation: The kristaloscillator is biased in a feedback amplifier so the crystal vibrates at its resonant frequency. The piezoelectric effect converts electrical energy into mechanical motion and back, causing the circuit to oscillate at a precise frequency. The crystal's high quality factor (Q) yields low phase noise and excellent frequency stability compared with many other oscillator types.

Frequency characteristics: Crystals can operate in fundamental mode or overtone modes, allowing higher frequencies by exciting higher harmonics. The actual oscillation depends on circuit design and load capacitance (CL); the specified frequency refers to the nominal mode under specified conditions. Crystals also age slowly and show temperature effects that depend on crystal cut (e.g., AT-cut quartz provides good mid-range stability).

Circuit implementation and packaging: The common configuration is the Pierce oscillator, widely used with microcontrollers. Other configurations such as Colpitts can be employed for special requirements. Crystals are packaged in metal cans or surface-mount packages and specified by nominal frequency and load capacitance (for example 16.000 MHz, CL 18 pF).

Applications and variants: Kristaloscillators provide timing and frequency references in clocks, processors, radios, and telecommunications equipment. They serve as the reference in phase-locked loops and clock distribution networks. For higher stability, temperature-compensated (TCXO) and oven-controlled (OCXO) variants are used.