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In the electronic world, what is the key principle of relaxing an oscillator?
A relaxation oscillator is a nonlinear electronic oscillator circuit that can generate a non-sinusoidal repetitive output signal such as a triangle or square wave. The circuit consists of a feedback loop and contains switching devices such as transistors, comparators, relays, operational amplifiers, or negative resistance devices such as tunnel diodes. It continuously charges the capacitor or inductor through a resistor until it reaches a certain threshold and then discharges it. In this process, the period of the oscillator mainly depends on the time constant of the capacitor or inductor circuit.
A relaxation oscillator differs from other types of electronic oscillators, such as linear oscillators, in that it uses amplifier feedback to stimulate resonant oscillations, thereby generating a sine wave.
Relaxation oscillators have a wide range of applications. Although it is suited to producing low frequency signals, usually below the audio range, it has nonetheless found a variety of uses, such as flashing lights (such as turn signals) and electronic beepers. They are also used in devices such as voltage controlled oscillators, inverters, switching power supplies, and function generators.
Interestingly, the concept of a relaxed oscillator is not limited to electrical engineering, but is also widely used in many fields of science for dynamical systems that also experience nonlinear oscillations and can use the same mathematical methods as electronic relaxed oscillators. Model to analyze. For example, geothermal geysers, networks of nerve cells, temperature-controlled heating systems, and the human heartbeat can all be modeled as relaxation oscillators.Relaxation oscillations are characterized by two alternating processes: a long relaxation period and a short impulse period, which alternate continuously.
Advances in Electronic Relaxation Oscillators
The first relaxed oscillator circuit, the astable multi-oscillator, was invented during World War I by Henry Abraham and Eugene Bloch. Baltasar van der Pol first distinguished between relaxation oscillations and harmonic oscillations in 1920 and coined the term "relaxation oscillator". He also derived the first mathematical model of a relaxed oscillator, the famous van der Pol oscillator model.
Relaxation oscillators can be divided into two categories based on their circuit structure: sawtooth, sweep or feedback oscillators and astable multi-oscillators. The energy storage capacitor in the sawtooth oscillator charges slowly but discharges almost instantly, so the output waveform is mainly a sawtooth waveform. In an astable multi-oscillator, the charging and discharging processes of the capacitor are carried out through resistors, and the output waveform contains rising and falling slopes.
Application of relaxation oscillator
Relaxation oscillators are widely used because of their relatively simple design and ease of fabrication in integrated circuits. They do not require inductors like LC oscillators, making them easier to screen and adjust. This type of oscillator plays an important role in time-base circuits, audio applications, and test instruments, such as the time base circuits of electronic instruments in the vacuum tube era and CRT oscilloscopes.
Although relaxation oscillators are easy to design, their phase noise and frequency stability are inferior to those of linear oscillators.
The Future and Challenges of Relaxation Oscillators
With the development of microelectronics technology, many simple relaxation oscillators have begun to use dedicated integrated circuits, such as the 555 timer chip, to replace the negative resistance devices (such as neon lamps or unipolar transistors) used earlier. In recent years, relaxation oscillators have played an indispensable role in various waveform generators, time delay circuits and other electronic applications.
Looking at the history, application and development of relaxation oscillators, this type of circuit undoubtedly plays an important role in electronic technology. However, with the change of technology, is it possible to have more efficient or more stable oscillator designs in the future? ?
