# Wien Bridge Oscillator

by Omri
Tags: bridge, oscillator, wien
 P: 35 Wien Bridge Oscillator Correct me if I'm wrong, but it looks like the ratio should be: $$\frac{V_O}{V_A} = \frac{Z_S + Z_P}{Z_P}$$ and the presentation says it's inverse. In addition, I don't really understand how the resistors R1 and R2 affect the system - am I supposed to multiply the right hand side of the equation above by $$1 + \frac{R_2}{R_1}$$ to get it right? The most significant question I have is, why does the circuit create sinusoidal voltage? I can get why oscillations will occur but I don't get why they should be sinusoidal. Thanks for you help :-)