The WIEN BRIDGE OSCILLATOR (figure shown below) largely relies on a pair of LR resonant networks for shifting the output signal by exactly 180 degree and one particular frequency. Then this phase-shifted signal is fed back to the non-inverting (1) input of the op amp. It is amplified and add force to the output signal. A strong sinusoidal waveform is generated. In Wien network, the two capacitors and both od the resistors are equal in value. The signal frequency is f = 1/2πRC.
The benfit of using the amplifier is that it is easily made tunable by making use of a dual ganged variable resistor for the 2 resistors in the Wien network.
