quartzoscillator

A quartz oscillator, or quartz-crystal oscillator, is an electronic oscillator that uses the mechanical resonance of a quartz crystal to generate an electrical signal with a very stable frequency. When placed in an amplifier circuit, the crystal acts as a highly selective resonator, enforcing feedback at its resonant frequency and producing a sustained oscillation with low phase noise.

Quartz crystals are cut from single crystals (AT-cut is most common for temperature stability; other cuts such as BT-cut or SC-cut are used for different temperature performance). The crystal is operated in either fundamental or overtone modes, allowing higher frequencies beyond the crystal’s fundamental resonance. The usual configuration is a Pierce-type oscillator using an inverting amplifier with the crystal in the feedback path. Frequency depends on crystal dimensions and cut, but load capacitance and drive level also affect it.

Performance and stability: Quartz crystals have a high quality factor, yielding a stable frequency; aging causes drift over time (often measured in parts per million per year); temperature affects frequency. Temperature-compensated (TCXO) or oven-controlled (OCXO) variants improve stability to a few parts per million or better. Common watch crystals operate at 32.768 kHz, used for timekeeping; higher-frequency crystals used in microcontrollers and radios range from a few megahertz to tens of megahertz.

Applications: quartz oscillators provide timing references for microprocessors, communications equipment, GPS, test and measurement devices, and telecom equipment. They are often integrated into crystal oscillator modules and used as frequency standards in local oscillators and clock generation circuits.

Variants and context: quartz oscillators compete with MEMS and SAW oscillators in some markets; quartz offers excellent long-term stability and low phase noise, though packaging and temperature control remain important to performance.