A Technical Introduction To Crystal Oscillators

By KVG Quartz Crystal Technology GmbH

Crystals and Crystal Oscillators are the most important components for frequency control applications like telecommunication and data transmission. The reasons are high frequency stability, high quality factor of the resonance, low temperature drift and reasonable prices. The wide range of crystal oscillators requires exact specification to ensure optimal performance. Standard Crystal Oscillators or XOs provide a stability of ±100ppm with 5V ( 3.3V) supply voltage in DIP-14, 14mm x 9mm or 7 x 5 mm SMD-packages. Applications are clocks for microprocessors and the consumer electronic market. Due to price-sensitive applications the requirements of the oscillators are mainly defined by case-style, frequency, stability, output signal and temperature range.

Professional applications in Telecommunication, Measurement Equipments, Satellite Navigation have much higher requirements such as tight stability, low impedance output (HCMOS or ECL/PECL for higher frequencies), low phase jitter and much longer lifetime of 15 years and more. To achieve a sufficient long term stability the complete oscillators need preaging and a stable process of the crystal production. While low-cost oscillators just give an overall stability all stability parameters are clearly defined for most of the professional oscillators.