Why does a sine wave oscillator output a sine wave?
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Recently, a question that has been bothering me is why the sine wave oscillator outputs a sine wave. Some friends may say that if the sine wave oscillator does not output a sine wave, can it still be called a sine wave oscillator? But no matter what, I want to figure this out. The oscillator is composed of an oscillation circuit. The oscillation circuit is a circuit that converts the DC power of the power supply into an AC signal of a certain frequency. The function is to generate AC oscillation as a signal source. The oscillation circuit can be an LC circuit or an RC circuit. Generally, medium and high frequency oscillators use LC oscillation circuits, which have high frequencies, small LC component values, small volumes, good frequency selection characteristics, and relatively pure output waveforms. In low-frequency oscillation circuits, the frequency is low and the LC component values used are large. At this time, the inductor coil used is very large, and the performance of the iron core coil is also poor. It is more appropriate to use an RC oscillation circuit. The oscillator circuit is composed of an amplifier with a positive feedback circuit. In the oscillation circuit that requires a very stable frequency, a quartz crystal oscillator must be used, which is very common in computers, electronic watches, etc. When an amplifier has positive feedback and reaches a certain level, the amplifier becomes an oscillator, that is, there is still an AC output in the absence of an external input signal, completing the energy conversion function. The oscillator can be considered as a special form of feedback amplifier. According to the different output waveforms, the oscillation circuit can be divided into two categories: non-sinusoidal oscillation and sinusoidal oscillation, and the sinusoidal oscillation circuit can be divided into LC oscillation circuit and RC oscillation circuit. The oscillation circuit is composed of triodes, resistors, capacitors and inductors (transformers or inductors). The function of the oscillation circuit is to generate an AC signal with a frequency ranging from below 1 Hz to above several hundred MHz. Therefore, it is used in industrial high-frequency induction furnaces, ultrasonic generators, semiconductor proximity switches, radios, televisions and other equipment.
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