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An electronic oscillator is an electronic circuit that produces a repetitive electronic signal, like a sine wave or a square wave. Oscillators are classified according to the waveshapes they produce and the requirements needed for them to produce oscillations.
Sinusoidal Oscillators
A sinusoidal oscillator produces a sine-wave output signal. To be precise, the output signal is of constant amplitude with no variation in frequency. Actually, something less than this is usually obtained. Factors such as class of amplifier operation, amplifier characteristics, frequency stability, and amplitude stability decide the degree to which the ideal is approached.
Signals ranging from low audio frequencies to ultrahigh radio and microwave frequencies are generated by Sine-wave generators. There are many low-frequency generators that make use of use resistors and capacitors combination, or inductor and capacitor combination to form oscillator.
RC oscillators generate waveform by making use of resistor and capacitor combination while LC oscillator generate waveform by making use of inductor and capacitor combination in network. RC OSCILLATORS are widely used in the audio-frequency range. On the other hand, LC OSCILLATORS are commonly used for the higher radio frequencies. They are not suitable for use as extremely low-frequency oscillators as the inductors and capacitors would be large in size, heavy, and costly to manufacture
A third type of sine-wave generator is the CRYSTAL-CONTROLLED OSCILLATOR
The crystal-controlled oscillator provides excellent frequency stability and is used from the middle of the audio range through the radio frequency range.
Nonsinusoidal Oscillators
Nonsinusoidal oscillators are used to generate complex waveforms, like square, rectangular, trigger, sawtooth, or trapezoidal. Since a sudden change or relaxation generally characterizes their outputs, they are often referred to as RELAXATION OSCILLATORS. The signal frequency of these oscillators is usually controlled by the charge or discharge time of a capacitor in series with a resistor. Some types, however, contain inductors that affect the output frequency. Thus, like sinusoidal oscillators, both RC and LC networks are used for determining the frequency of oscillation. There are various types of oscillators designed based on nonsinusoidal oscillators concept. This includes MULTIVIBRATORS, BLOCKING OSCILLATORS, SAWTOOTH GENERATORS, and TRAPEZOIDAL GENERATORS.
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