Ceramic resonators are used as mechanical resonators in oscillating circuits. The principle of operation is as piezoelectric resonator and the oscillation depends on the resonance frequency, the frequency often ranges from a few hundred KHz to a few tens of MHz. The oscillation frequency depends mainly on the thickness of the ceramic core of the resonator and the type of material used while it is little affected by external variable elements. The oscillator is characterized by a good stability vs. temperature and long-term stability (aging) and can even replace the quartz crystal resonators in less sophisticated applications. Thanks to their low cost and small size ceramic resonators are often used with microprocessors, BUS data ports , TTL, CMOS, digital and control audio application, floppy disk drive, telephony, commercial and consumer equipment, etc... The difference between the 2 and 3 pins types is the built in loading capacitors in the 3 pins type.
