1. Ordinary Crystal Oscillator (SPXO):

This is the most basic type of crystal oscillator, with a simple structure and low cost. It consists of a crystal and a peripheral circuit, directly outputs a fixed frequency signal, and has relatively low frequency stability. It is generally suitable for occasions where frequency accuracy is not too high, such as some simple consumer electronics, toys, etc.

2. Temperature Compensated Crystal Oscillator (TCXO):

Since temperature changes have a greater impact on the resonant frequency of the crystal, in order to improve frequency stability, temperature compensated crystal oscillators came into being. It uses a built-in temperature compensation circuit to automatically adjust the crystal's load capacitance or other related parameters according to changes in ambient temperature to compensate for the impact of temperature on frequency. TCXO has higher frequency stability than SPXO and is often used in communication equipment, automotive electronics, industrial control and other fields that require high frequency accuracy.

3. Voltage Controlled Crystal Oscillator (VCXO):

The output frequency of this crystal oscillator can be adjusted by the input control voltage. By changing the size of the control voltage, the crystal's load capacitance or other related parameters can be changed, thereby achieving fine-tuning of the output frequency. VCXO is often used in applications that require adjustable frequency, such as phase-locked loop (PLL) circuits, frequency synthesizers, wireless communication equipment, etc., which can achieve fast switching and precise control of frequency.

4. Oven-controlled crystal oscillator (OCXO):

In order to obtain higher frequency stability, the oven-controlled crystal oscillator places the crystal in a constant temperature tank and keeps the crystal at a constant temperature through heating or cooling devices, thereby greatly reducing the impact of temperature on frequency. OCXO has extremely high frequency stability and is usually used in occasions with strict frequency accuracy requirements, such as aerospace, satellite communications, high-end test and measurement equipment, etc.

5. Differential Crystal Oscillator:

Output differential signal, compared with single-ended output crystal oscillator, has better anti-interference ability and signal integrity, can effectively reduce electromagnetic interference (EMI), suitable for high-speed digital circuits and applications with high signal quality requirements.