Crystals

A quartz crystal has electromechanical characteristics that allow it to operate in an electronic circuit as an oscillator with the addition of load capacitors and is an integral part of crystal electronics. It generates an electric signal with a specific frequency. It is valuable as an oscillator because the frequencies do not vary along with changes in temperature. Quartz crystal oscillators are important components in a long list of consumer devices, including smartphones, radios, medical devices, cars and communications transmitters.

Crystal wafers are cut at specific angles that vibrate at precise frequencies when an electric field is applied. What makes components of electronic crystals so unique and popular for use in electronic devices is that they are generally very stable across a broad range of temperature changes. Their resistance to changes in environmental factors makes them reliable in terms of maintaining their precise frequencies.

The most important functions of quartz crystal components are maintaining stable frequencies and generating steady reference signals. They are incorporated into electronic devices that rely on a stable frequency to be able to send and receive necessary information. The steady reference signals produced by quartz crystal components help synchronize the various parts of electronic devices, such as clocks, that rely on precise timing to function accurately.

The AT-cut quartz crystal is very popular and is typically found in electronic devices that run on a frequency range of 1MHz to approximately 200MHz. The BT-cut quartz crystal is used at slightly higher frequencies. The SC-cut quartz crystal was originally developed for use in crystal ovens as it is particularly resistant to premature aging and effective at noise minimization while operating.

Quartz crystal units are so prevalent in electronics because of their role in producing stable frequencies and steady reference signals. Quartz crystal oscillators operate as part of an integrated circuit. They are frequently used in radio transmitters and receivers as well as any electronic device that depends on a clock signal.

Quartz crystals and ceramic resonators operate in similar ways because they both vibrate when exposed to AC signals, but they have different characteristics. Quartz crystals maintain accurate frequency stability without requiring significant power. On the other hand, ceramic resonators are more frequently found in microprocessor components where slight fluctuations in frequency are acceptable. Essentially, quartz crystals are preferred over ceramic resonators for use in electronic devices that are subject to temperature variations and environmental changes and require maintaining an extremely accurate frequency.

A quartz crystal can operate in both series and parallel resonance. The parallel resonance is higher by just several kilohertz than the series resonance. A quartz crystal under 30 MHz operates as an inductive reactance as it is between series and parallel resonance. A quartz crystal above 30 MHz and up to higher than 200 MHz is more likely to operate at series resonance.

Spurious frequencies are also referred to as “unwanted responses” and may be generated when a quartz crystal is vibrated, which can modulate the resonant frequency slightly. An SC-cut crystal will likely be less vulnerable to spurious frequencies from external vibrations. In addition, spurious frequencies may also be found in quartz crystals that are operating at series resonance or being pulled away from the primary mode. This typically involves the work of a series inductor or capacitor. Also, significant temperature changes in conjunction with the series resonance of the quartz crystal can result in spurious frequencies.

The range of frequencies available for quartz crystals that are made for oscillation is quite broad. They range from just several kilohertz to up to hundreds of megahertz. Generally, the most commonly used crystal resonance frequency is from 20MHz to 40MHz especially for wireless communication.

When it comes to oscillator for crystal electronics, quartz crystal is the most commonly found material. Quartz Crystal is manufactured to maintain precise frequencies when used in operating an electronic device.

Quartz Crystal is grown and manufactured for specific purposes in electronic devices. For example, the AT-cut crystals are made specifically for oscillator devices. High-quality crystal quartz is used in premium electronic devices and contains minimal levels of defects or impurities. They are manufactured artificially in strictly controlled environments by starting with a seed crystal at a temperature of about 350°C. At a pressure of approximately 1,000 atmospheres, it generally takes between 45 to 90 days for a synthetic quartz crystal to form in a growing furnace.

There are left-handed and right-handed quartz crystals. While their optical rotations are certainly different, they share many of the same characteristics. Depending on the cut edge of the crystal, both left-handed and right-handed quartz crystals can be used in crystal oscillators. However, right-handed quartz crystals are generally more common in manufacturing.

The frequency stability of a quartz crystal is essentially set in stone upon its physical shape and the precise angle of the final cut of the quartz crystal. Along those lines, the stability of the crystal frequency is based on the crystal’s Q factor.

The angle of the cut of the quartz crystal establishes the crystal’s sensitivity to changes in temperature. Changes in temperature exposure for the crystal can alter the crystal’s operating frequency. Some crystals feature temperature-dependent cuts in order to reduce the crystal’s temperature or frequency dependence.

A quartz crystal’s frequency is subject to variations as a result of mechanical stress. They can disrupt the crystal during the manufacture and operating processes, including pressure within the crystal enclosure and movement of electrodes. An SC-cut quartz crystal is typically less reactive to mechanical stresses.

When quartz crystals age, their resonant frequency moves slightly. Even though the resulting variations in frequency levels may seem relatively minor, they can have major consequences for the proper functioning of the electronic device in which they are used. The quartz crystals used in Suntsu’s high-quality products reflect strictly controlled manufacturing environments and the chemical etching process that minimizes the entrance of contaminants. Similarly, the circuit design of the device in which the quartz crystal will be used is made specifically to keep low drive levels and slow the crystal aging process in turn.

Shock-induced changes to the quartz crystal’s environment can result in significant and lasting mechanical damage to the crystal itself, which will ultimately accelerate the aging process. It may first present as an immediate change to the frequency of the crystal oscillator. If the surface of the crystal is smooth and free from imperfections, then it is more likely to resist external shocks. The process of chemically polishing the surface of the quartz crystal can increase its resistance to external shocks and other mechanical damage.

There are a variety of reasons why a quartz crystal may experience changes in its frequency, which are also known as frequency fluctuations. Temperature changes, vibrations, mechanical shocks, orientation changes and thermal noise are some of the common causes of frequency variations in quartz crystals. Changes in the acceleration and vibrations tend to overpower the impact of any other variations in noise levels that could induce frequency changes in a quartz crystal.

AT-cut and SC-cut quartz crystals feature distinct temperature stability curves. Primarily, the AT-cut quartz crystal is the superior choice for a broad range of temperatures. This helps the AT-cut crystal maintain its status as one of the most commonly used types of crystals in electronic devices that rely on crystal oscillators beginning at 1MHz. The upper limit of 200 MHz for many commercial quartz crystal oscillators continues to expand with cutting-edge innovations in the manufacturing and processing of the quartz crystals. On the other hand, the SC-cut quartz crystal, also known as the “stress compensated” quartz crystal, was manufactured mainly for use in crystal ovens due to its reduced sensitivity to changes in thermal or mechanical stress. In addition, the phase noise and relatively slower aging profile of SC-cut crystals make them ideal for use in crystal ovens.

Quartz crystal oscillators are a widely used type of electronic oscillator circuit that relies on the mechanical resonance from the vibrations of a quartz crystal. The specific frequencies that are produced from a quartz crystal oscillator are used in all types of devices that run on clock time as well as for radio transmitters and receivers. Voltage is applied to an electrode to generate an electric field to distort the quartz crystal. The specific frequency produced by the quartz crystal determines how it will ultimately be used in an electronic device. When a quartz crystal is manufactured for an oscillator, the specific frequency can vary from only a few kilohertz to several hundreds of megahertz.

The impedance of a crystal is generally measured in terms of its reactance against frequency or resistance against frequency. The slope of the quartz crystal impedance changes according to changes in the frequency of the crystal.

The reactance of the quartz crystal will vary along with changes in the quartz crystal’s frequency. An increase in the frequency of the quartz crystal results in a similar increase in inductive reactance. However, an increase in the frequency of the quartz crystal also means a reduction in the capacitive reactance. Reactance is generally like resistance as smaller currents from the same level of voltage applied to the quartz crystal result from larger reactance.

When there is low impedance to the flow at a particular frequency, then series resonance can occur. Series resonance is achieved when the inductive reactance within a circuit is at the same level as the circuit’s capacitive reactance. Series resonant is useful for magnifying the signal voltage from a signal transmitter as well as the current for a specific frequency.

When there is high impedance to the flow at a particular frequency, then parallel resonance can occur. A parallel resonant circuit is more frequently used in electronic devices than a series resonant circuit. In the parallel resonance condition, a circuit uses the minimum current because the reactive part of the current has been suppressed.

A crystal oscillator circuit uses the voltage supplied from the crystal quartz resonator. The crystal oscillator circuit works by amplifying that voltage and then sending it back to the crystal quartz resonator. When the quartz crystal expands and contracts repeatedly, a specific resonant frequency is generated. The particular resonant frequency is based on the size and the cut of the quartz crystal used in the crystal oscillator circuit. Oscillation within the particular device is sustained by the matching of the resonant frequencies produced to those lost by the crystal oscillator circuit.

Almost every one of the microprocessors used in the production of electric devices is made with a quartz crystal oscillator. The quartz crystal oscillator works as the frequency-setting and maintaining component of the microprocessor and is highly regarded for its strong characteristics of frequency accuracy and stability compared to other microprocessor options. Microprocessor crystal quartz clocks are made up of a quartz crystal and two ceramic capacitors with values between 15 to 33pF.