A new interpretation of active crystals, 4 major categories of active crystals
“Crystal oscillators have many applications in life. According to the characteristics of crystal oscillators, we can divide them into active crystal oscillators and passive crystal oscillators.
Crystal oscillators have many applications in life. According to the characteristics of crystal oscillators, we can divide them into active crystal oscillators and passive crystal oscillators.
1. Introduction to Active Crystal Oscillator
In electronics, circuits containing transistor components are usually referred to as “active circuits” (such as active speakers, active filters, etc.), while circuits consisting only of RC components are referred to as “passive circuits.” Crystal oscillators in computers are also divided into passive crystal oscillators and active crystal oscillators. Passive crystal oscillator and active crystal oscillator have different English names. Passive crystal oscillator is crystal (crystal), while active crystal oscillator is called oscillator (oscillator). Passive crystal oscillator is a non-polar component with 2 pins. It needs the help of a clock circuit to generate an oscillating signal and cannot oscillate by itself. Therefore, the term “passive crystal oscillator” is not accurate; an active crystal oscillator has 4 pins. It is a complete oscillator, in which in addition to the quartz crystal, there are transistors and resistance-capacitance components, so the volume is relatively large.
The frequency stability of the quartz crystal oscillator can reach 10^-9/day, or even 10^-11. For example, for a 10MHz oscillator, the frequency change within a day is generally not more than 0.1Hz. Therefore, the crystal oscillator can be regarded as a constant reference frequency source (quartz watches and Electronic watches all use quartz crystals for timing reference frequencies). From the birth of the PC to the present, a 14.318MHz quartz crystal oscillator has been used as a reference frequency source on the motherboard. In addition to this 14.318MHz crystal on the motherboard, you can also find a 32.768MHz crystal, which is used in the real-time clock (RTC) circuit to Display the precise time and date.
2. 4 categories of active crystal oscillators
Crystal oscillators are divided into active crystal oscillators and passive crystal oscillators. According to the function and implementation technology of active crystal oscillators (crystal oscillators), they can be divided into the following four categories:
1. Temperature compensated crystal oscillator (TCXO).
Its solution to temperature stability adopts some temperature compensation methods. The main principle is to control the output frequency of the crystal oscillator after the temperature information is appropriately transformed by sensing the ambient temperature, so as to achieve the effect of stabilizing the output frequency.
Features: Use the thermal compensation network to improve the temperature characteristics of the quartz crystal, which can meet the needs of a wider temperature range; frequency range: 1-40 MHz; frequency stability: 5&TImes;10-6～5&TImes;10-7.
2. Ordinary crystal oscillator (SPXO).
This is a simple crystal oscillator, usually called a clock oscillator, which is completely completed by the free oscillation of the crystal. This type of crystal is mainly used in occasions where stability is not required.
Features: It directly reflects the performance of the quartz crystal used; the working frequency range is usually 1KHz～250 MHz; the frequency stability is 10-4～10-5; it is generally used for local oscillator sources or intermediate signals.
3. Voltage controlled crystal oscillator (VCXO).
This is classified according to whether the crystal oscillator has a voltage control function. A type of crystal oscillator with a voltage control input pin is called VCXO.
Features: Frequency can be changed with external modulation voltage; Frequency range: 1～250MHz; Frequency stability: Ordinary crystal oscillator voltage control is ≤(1～2)&TImes;10-3fo/n2, high stability crystal oscillator can be fine-tuned 10-7. Frequency fine-tuning or phase lock synchronization.
4. Voltage-controlled temperature-compensated oscillator (VC-TCXO)
It is easy to understand that it combines the two functions of pressure control and temperature compensation.
At present, these types of crystal oscillators are mainly imported, and Japan KDS is one of the three largest manufacturers in the world. KDS is Japan’s Dashinku Corp., established in 1951, and has been more than 50 years old. history. It is one of the world’s leading three crystal oscillator manufacturers. Its manufacturing plants are mainly distributed in ten manufacturing centers in Japan, China, Taiwan, Thailand, and Indonesia. Among them, Tianjin Factory is the largest single manufacturing plant in the world’s crystal oscillator industry. It is also the world’s largest TF type (mainly 32.768KHz) crystal oscillator manufacturing plant.