WEIN BRIDGE OSCILLATOR

A Wien bridge oscillator generates sine waves to a large range of frequencies. It is based on a bridge circuit developed for the measurement of impedances. The bridge comprises of four resistors and two capacitors. Non inverting amplifier used in amplifier stage does not introduce any phase shift. Hence there is no need of phase shift through feedback network is required in order to satisfy the Barkhausen criteria. If the feedback network elements are chosen properly, the phase shift of the signal input to the amplifier is zero at certain frequency. Since the amplifier is non-inverting which introduce zero phase shift plus the feedback network zero phase shift, the total phase shift becomes zero around the loop hence the required condition of oscillations. ADVANTAGE: 1) Good frequency stability. 2) Very low distortion. 3) Easy to tune. R3 and R4 are part of amplifier The lower 2 branches are part of RC feed back circuit. Series rc circuit acts like High pass filter and Parallel circuit act as low pass filter. AB=1 B=1/3( by rc circuit)(feedback fraction)( ratio of voltages) A=3(by amplifier) A= 1+(R4/R3)