Crystal oscillators are also classified into two types: passive crystals and active crystal oscillators.A passive crystal is a crystal, and an active crystal is called an oscillator. A passive crystal oscillator needs a clock circuit to generate an oscillating signal and cannot oscillate itself. Therefore, the term “passive crystal oscillator” is not accurate; an active crystal oscillator is a complete resonant oscillator. Both quartz crystal oscillators and quartz crystal resonators are an electronic device that provides a stable circuit frequency. The quartz crystal oscillator uses the piezoelectric effect of the quartz crystal to start the oscillation, while the quartz crystal resonator works by using the quartz crystal together with the built-in IC.
The oscillator is directly applied to the circuit. When the resonator is working, it is generally required to provide 3.3V to maintain the operation. The oscillator has one more important technical parameter than the resonator: resonant resistor (RR), and the resonator has no resistance requirement. The size of the RR directly affects the performance of the circuit, so this is an important parameter for each merchant's competition.