Nowadays, various resonators are widely used in the electronic field. Among these resonators, there are two main materials used, namely quartz crystal and ceramic (ceramic resonator).

Quartz crystals are used for crystal oscillators and ceramics are used for ceramic resonators. Both have the same purpose, which is to generate oscillation frequencies by vibrating when an input voltage is supplied to them. However, there are also some differences between them, so they have different application scope.

What is a crystal oscillator?

An oscillator is a circuit that generates frequency with the help of a tuned circuit and the frequency generated is called the oscillation frequency. Likewise, a crystal oscillator is an electronic circuit or device used to generate a stable frequency with the help of a crystal instead of a tuned circuit. When a crystal vibrates, it acts like a resonator and therefore produces an oscillation frequency. Resonator circuits use crystals to produce oscillations, hence the name Crystal Oscillator.

What is a ceramic resonator?

Similar to a crystal oscillator, a ceramic resonator is an electronic circuit or device used to produce an output at an oscillating frequency with the help of ceramic as a resonant piezoelectric material. The material can have two or more electrodes that when connected to an oscillator circuit produce mechanical vibrations and therefore an oscillating signal of a specific frequency.

When the resonator is operating, mechanical vibrations generate an oscillating voltage due to the piezoelectric material (i.e. ceramic), which is then attached to the electrodes as an output. The inverse concept is used in the case of the inverse piezoelectric effect.

Note: The crystal oscillator will not be made of ceramic material, because compared to quartz material, ceramic material does not have enough stability, and the accuracy is not good. Crystal resonators are made of quartz and ceramic, so ceramic resonators are one type of crystal resonators, but it cannot be said that crystal resonators are ceramic resonators.

The main differences between crystal oscillators and resonators

Although a crystal oscillator has the same working process as a resonator and produces frequency oscillation as an output, they have some differences in nature in many cases because the oscillator replaces the resonator, as follows:

• In terms of structure, crystal oscillators have 4 or more pins, including 4 pins. Crystal resonators usually have 2 or 4 pins. There are no crystal resonators with more than 4 pins;
• Frequency range, the Q factor of crystal oscillators is much higher than that of ceramic resonators, so the frequency range of crystal oscillators is 10kHz-100MHz, while the frequency range of ceramic resonators is 190kHz-50MHz;
• Output frequency, crystal oscillator provides high stability frequency output, ceramic resonator also provides not as good stability output as crystal oscillator. In terms of output frequency accuracy, crystal oscillators provide more accurate output than ceramic resonators, which are sensitive to parameters such as temperature. The accuracy of the oscillator is 10ppm-1000ppm, while the accuracy of the resonator is 0.1%-1%;
• Influence of parameters – For ceramic resonators, the thickness of the ceramic material will determine the output resonant frequency, while for crystal oscillators, the resonant frequency output depends on the size, shape, elasticity and speed of the sound in the material. Crystal oscillators have very low temperature dependence, i.e. they are very stable even if the temperature changes, and ceramic resonators have a little more temperature dependence than crystal oscillators. For quartz crystal oscillators, the output characteristics depend on the vibration mode and the angle at which the crystal is cut, whereas in a resonator it is mainly a matter of thickness;
• Tolerance and Sensitivity – Crystal oscillators have lower tolerance to shock and vibration, while ceramic resonators have relatively higher tolerance. Crystal oscillators have low ESD (electrostatic discharge) tolerance, while ceramic resonators have high ESD tolerance. Oscillators are more sensitive than resonators, and the sensitivity can be compared in terms of radiation. Quartz has a frequency tolerance of 0.001%, while PZT has a tolerance of 0.5%;
• Capacitor dependence – Resonators may have internal capacitors or sometimes require external capacitors, while oscillators require external capacitors, their values depend on the crystal they are designed to operate on;
• Materials used – Crystal oscillators are made of quartz as the piezoelectric resonator material, while ceramic resonators are made of lead zirconium titanate (PZT), which is called a high-stability piezoelectric ceramic material. Crystal oscillators are difficult to manufacture, while ceramic resonators are easy to manufacture;
• Applications – Ceramic resonators are used in microprocessor applications where frequency stability is not important, while crystal oscillators can be found in everything from televisions to children’s toys with electronic components. Resonators are suitable for low-speed serial port communications, while crystal oscillator frequencies can also be used to support high-speed serial communications. The resonator does not have a frequency that can be used for high-speed serial port communications. In terms of clock based applications, resonators are not very suitable for real time clocks/timing/wall clocks and require variable capacitors for tuning, oscillators are suitable for timing/RTC/wall clock etc. applications and may drift tuning by a few minutes per year.

Conclusion

From the above analysis, it is not difficult to see that quartz is a material of crystal oscillators. Of course, the material is also made of ceramics. However, the accuracy of quartz crystal oscillators is higher than that of ceramic crystal oscillators, so it is widely used in the market.

Essentially, a crystal oscillator means that the crystal has an oscillation function, so a crystal oscillator is equal to an active crystal oscillator, which means it has its own voltage and can oscillate on its own without the need for external components to help start the oscillation, while a ceramic resonator is equal to Passive crystal oscillator. However, both passive crystal oscillators and active crystal oscillators belong to crystal oscillators.