Oscillator circuit must have the following three elements:
1.Oscillatory circuit or frequency determine element.
2.Amplifier.
3.Positive feedback network.
The Oscillatory circuit or a frequency-determining element can be an inductance-capacitance network(L-C tank),resistance-capacitance (R-C network,or a quartz crystal,depending on the frequency and waveshape desired.
The electronic amplifier receives dc power from the battery or dc power supply and converts it into ac power for supply to the tank circuit.The oscillations occurring in the tank circuit are applied to the input of the electronic amplifier.Because of the amplifying properties of the amplifier,we get increased output of these oscillations.This amplified output of oscillations is because of dc power supplied from the external source( a battery or power supply).The output of the amplifier can be supplied to the tank circuit to meet the losses.
The feedback network supplies a part of the output power to the frequency-determining element in correct phase to aid the oscillations.In other words,feedback circuit must be a positive feedback network.The block diagram of an oscillators is shown in fig.
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