Various resonators are used in numerous applications in the field of electronics. Of these resonators, the two main materials used are quartz crystals and ceramics (to make ceramic resonators). Quartz crystals are used for crystal oscillators and ceramics are used for ceramic resonators . They all have the same property of generating an oscillating frequency by vibrating when an input voltage is supplied to them. But there are also some differences between the two that differentiate them and therefore apply them to different applications.
What is a crystal oscillator?
An oscillator is a circuit that generates an oscillation frequency with the help of a tuned circuit. Likewise, a crystal oscillator is an electronic circuit or device that produces a stable frequency with the aid of a crystal rather than a tuned circuit. When a crystal vibrates, it acts like a resonator and thus produces an oscillation frequency. The resonator circuit uses a crystal instead to generate oscillation, so it is called a crystal oscillator ( Crystal Oscillator for short ) . The symbol and circuit of the crystal oscillator are shown in the following figure:
What is a ceramic resonator?
Similar to a crystal oscillator, a ceramic resonator is also an electronic circuit or device that uses ceramic as a resonant piezoelectric material to generate an output at an oscillating frequency. This material can have two or more electrodes that, when connected to an oscillator circuit, generate mechanical vibrations and thus an oscillating signal of a specific frequency. The circuit of a resonator is similar to that of a crystal oscillator, as shown in the following figure:
When the resonator works, an oscillating voltage is generated due to the mechanical vibration of the piezoelectric material (ie, ceramic), and then the oscillating voltage is used as an output.
Crystal Oscillators and Resonators
Although they have the same working process and produce frequency oscillations as output, they have some differences in performance, so oscillators replace resonators in many cases:
§Frequency range - Crystal oscillators have a much higher Q factor than ceramic resonators, crystal oscillators have a frequency range of 10 kHz – 100 MHz, while ceramic resonators have a frequency range of 190 kHz – 50 MHz
§Output - Crystal oscillator provides high stability frequency output , ceramic resonator also provides stable output, but crystal oscillator is a little better. In terms of output frequency accuracy, crystal oscillators provide a more accurate output than ceramic resonators, which are sensitive to parameters such as temperature. Oscillators have an accuracy of 10ppm-1000ppm (parts per million of 1ppm), while resonators have an accuracy of 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 velocity of the sound in the material. The effect of temperature on crystal oscillators is very low, they are very stable even with temperature changes, while the effect of temperature on ceramic resonators is a little more than crystal oscillators. For quartz crystal oscillators, the output characteristics depend on the vibration mode and the angle at which the crystal is cut, while in ceramic resonators it is mainly the thickness that has a greater effect.
§ Tolerance and Sensitivity - Crystal oscillators are less tolerant to shock and vibration, while ceramic resonators are relatively more tolerant. 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 0.5% tolerance.
§ Capacitor Dependency - Resonators may have internal capacitors or sometimes external capacitors, while oscillators require external capacitors, their value depends on the crystal designed.
§ Materials used - Crystal oscillators are made of quartz as piezoelectric resonator material, while ceramic resonators are made of lead zirconium titanate (PZT), a material known as high stability piezoelectric ceramic material. Crystal oscillators are more difficult to manufacture than ceramic resonators.
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Applications - Ceramic resonators are used in microprocessor applications where frequency stability is not critical, while crystal oscillators are more widely used and can be found in products ranging from computers to children's toys with electronic components. The resonator is suitable for low-speed serial port communication, while the frequency of the crystal oscillator can be used to support high-speed serial communication. The resonator does not have a frequency available for high-speed serial port communication. In terms of clock based applications, resonators are less suitable for real time clocks/timing/wall clocks, whereas oscillators may be suitable for timing/RTC/wall clocks if tuned with variable capacitors, expect a few minutes of drift per year if untuned .