Quartz resonator(crystal oscillator)
Quartz resonator also known as quartz crystal, commonly known as crystal oscillator, is a kind of resonant element made of the piezoelectric effect of quartz crystal. It can form a quartz crystal oscillator with the use of semiconductor devices and resistance components. Electronic components for stabilizing frequency and selecting frequency have high accuracy, stability and high Q value. It is widely used in color TV, mobile phone, watch, radio, video recorder, video player, camera and other circuits.
l Classify the quartz crystal
(1) The type of quartz crystal
According to the package shape, the crystal oscillator has several kinds of metal shell, glass shell, bakelite shell and plastic seal.
(2)According to frequency stability, there are common and high precision. As long as the frequency and volume meet the requirements, many of the crystal oscillator components can be used interchangeably.
( 3 ) The model of quartz crystal is made up of three parts. The first part is made of alphabet, and the second part uses one letter to indicate the way of cutting quartz, and the third part uses Arabic numerals to distinguish the resonator key parameters, performance and outline dimensions. For example, JF6. 000 indicates that the quartz resonator is a metal shell. The FT cutting mode has a resonant frequency of 6 MHz.
l The characteristics and parameters of the quartz crystal
1.The quartz crystal is characterized by a high quality factor, with two resonant phenomena in series and parallel, which constitute a variety of oscillating circuits, but there are only two basic circuits, which are parallel crystal oscillators and series crystal oscillators. The former is in the form of parallel resonance, while the latter is in the form of series resonance.
The quartz crystal resonator is made of piezoelectric effect. When the frequency of the applied alternating voltage is equal to the natural frequency of the chip, the amplitude of mechanical vibration will increase sharply. This phenomenon is called piezoelectric resonance.
The oscillator, consisting of a quartz resonator, is characterized by a high frequency stability, for example, a 10MHz oscillator, a periodic frequency change less than 0.1~0.01Hz, or even less than 0. 0001Hz.
2.The main electrical parameters of the crystal oscillator are nominal frequency fo, load capacitance Ci, excitation level (power) and temperature,frequency difference and so on.
( 1 ) The nominal frequency of the quartz crystal is marked with a nominal frequency, and the frequency stability is the highest when the circuit operates at this nominal frequency. This nominal frequency is usually measured on a quartz crystal with a certain load capacitance before the finished product is manufactured.
( 2 ) The load capacitance quartz resonator should pay more attention to its load capacitance and excitation level. The load capacitance refers to the total capacitance from the two ends of the resonator pin to the direction of the oscillation circuit. The standard values of load capacitance are : 15pF, 20pF, 30pF, 50pF or 100pF. The load capacitance determines the operating frequency of the oscillator together with the resonator. By adjusting the load capacitance, the operating frequency of the oscillator can be adjusted to the nominal value .
The load capacitance should be selected according to the specific situation. The load capacitance is too large, but the effect of stray capacitance decreases, but the fine-tuning rate decreases; the load capacitance is too small, the micro modulation rate increases, but the stray capacitance influence increases, the equivalent resistance increases.
The load capacitance should be selected according to the specific situation. The load capacitance is too large, but the effect of stray capacitance decreases, but the fine-tuning rate decreases; the load capacitance is too small, the micro modulation rate increases, but the stray capacitance influence increases, the equivalent resistance increases.
The load capacitance of the crystal oscillator has the difference between high and low. The lower is generally only a dozen of pF to hundreds of pF, the higher the infinite, the difference between the two, can not be mixed, otherwise it will make the oscillation frequency deviate from the circuit can work normally, the two types of different load capacitance are also different.
Capacitors with low load capacitance are connected in series with dozens of skin capacity capacitors; high load capacitance not only can not be series capacitor, but also parallel number skin method small capacity capacitor ( the distributed capacitance of the external circuit can sometimes replace the parallel small capacitor ). In addition to clearly marking the nominal frequency on the shell of each crystal, the difference between other performance parameters is distinguished by model and grade symbols. As for the nominal frequency of 4. 43 MHz.
( 3 ) Excitation level
Excitation level is the effective power consumed by the resonator. The standard value of excitation level is 0.lmW and 0.5mW, 1 mW, 2, 4 mW. The excitation level should be reasonably determined when it is used in practice. The excitation level is small, the frequency is unstable, and even it is not easy to start; when the excitation level is strong, the vibration is easy, but the frequency change is increased, and the quartz is broken when it is too strong.
If you want to know more, our website has product specifications for the oscillators, you can go to ALLICDATA ELECTRONICS LIMITED to get more information.