Principle of the oscillator Have you brought the microphone close to the speaker and have made an unpleasant sound? This is the phenomenon, the HOWLING.
As for some oscillators, the principle which is the same as the howling is used. It is the way of returning the output of the amplifier to the input.
The feedback circuit of the oscillator has the following role mainly.
It fixes the oscillation frequency.
It controls to oscillate at the specific frequency. It returns only the specific frequency signal to the input.
It controls the input level which is necessary to oscillate.
The amplifier becomes the saturation state when the signal which returns to the amplifier through the feedback circuit is too big and the beautiful signal doesn't come out.
It adjusts the phase of the frequency which is necessary to oscillate.
The phase means the position of the signal. At the electronic circuits, phase of the input and the output depends on capacitors, the coils, the amplifier itself. Because it is, it doesn't oscillate when not adjusting the phase of the input signal.
There is a circuit to be making have the role of the oscillation frequency's, output's not changing by the temperature in addition to above-mentioned, too.