Active vs. Passive Crystal Oscillators: Differences and Selection

I. Definitions and Working Principles

1. Active Crystal Oscillator (XO)An active crystal oscillator contains an internal oscillator circuit that directly generates stable high-frequency signals. When voltage is applied, it begins to oscillate and produces a signal with a known frequency.

2. Passive Crystal Oscillator (Crystal Resonator)A passive crystal is simply a quartz crystal resonator without an internal oscillator. It operates based on the piezoelectric effect - when an external voltage is applied, the quartz crystal mechanically deforms, producing stable frequency changes.

II. Characteristic Differences

1. StabilityActive oscillators typically offer higher stability because their internal circuitry provides stronger driving force. Passive crystals depend more on external voltage conditions and the quality of the quartz crystal itself.

2. Size and Power ConsumptionWith their built-in oscillator circuitry, active crystals generally have larger size and higher power consumption, making them less suitable for miniaturized designs.

III. Application Selection

Choose active crystals for applications requiring exceptional stability such as high-frequency communications and radar systems.

Choose passive crystals when size and power are strictly limited or when circuit simplification is a priority.

Conclusion

While both are quartz-based resonators, the presence or absence of an internal oscillator creates significant differences in stability, size, and power consumption. Understanding these differences helps make appropriate selections for specific applications.

Would you like to see a side-by-side comparison table of these specifications, or learn about specific application scenarios for each type?