Active Crystal Oscillator - Voltage Controlled Oscillator

zkj2014

Active Crystal Oscillator - Voltage Controlled Oscillator [Copy link]

Since its birth, oscillators have played an important role in the fields of communications, electronics, navigation, aerospace, and medicine, and have a wide range of uses. In the early days of radio technology, it was used to generate high-frequency carrier voltage in transmitters and as a local oscillator in superheterodyne receivers, becoming a basic component of transmitting and receiving equipment. With the rapid development of electronic technology, the use of oscillators has become more and more extensive, but compared with the price of ordinary crystal oscillators , the price is often several times higher than that of ordinary crystal oscillators.

For example, in radio measuring instruments, it generates sinusoidal signal voltages of various frequency bands; in thermal processing, heat treatment, ultrasonic processing and some medical equipment, it generates high-power high-frequency electric energy to heat the load; some electrical equipment is controlled by contactless switches made of oscillators; electronic clocks and electronic watches use oscillation circuits with high frequency stability as timing components, etc. Especially in communication system circuits , voltage-controlled oscillators (VCOs) are key components, especially in phase-locked loop circuits, clock recovery circuits and frequency synthesizer circuits. It is no exaggeration to say that in the field of electronic communication technology, VCOs are almost as important as current sources and op amps. Active crystal oscillators are divided into voltage-controlled oscillators and temperature-compensated oscillators, voltage-controlled temperature-compensated oscillators, and ordinary oscillators. Compared with ordinary crystal oscillators, voltage-controlled oscillators (VCOs) have more electronic control devices in the resonant circuit, such as varactor diodes; generally, voltage-controlled oscillators (VCOs) exist in the form of Clapp oscillators to ensure the stability of the circuit operating point and Q value.

The quartz crystal oscillator uses the piezoelectric effect of the quartz crystal to start oscillation, while the quartz crystal resonator uses the quartz crystal and the built-in IC to work together. The oscillator is directly applied to the circuit, and the resonator generally needs to provide a 3.3V voltage to maintain operation. The oscillator has one more important technical parameter than the resonator: the resonant resistance (RR), and the resonator has no resistance requirement. The size of RR directly affects the performance of the circuit, so it is an important parameter for competition among merchants. Crystal oscillators are also divided into two types: passive crystal oscillators and active crystal oscillators. The English names of passive crystal oscillators and active crystal oscillators (resonance) are different. Passive crystal oscillators are crystals, while active crystal oscillators are called oscillators. Passive crystal oscillators need the help of a clock circuit to generate an oscillation signal and cannot oscillate by themselves, so the term "passive crystal oscillator" is not accurate; active crystal oscillators are complete resonant oscillators. Quartz crystal oscillators and quartz crystal resonators are both electronic devices that provide stable circuit frequencies.