# Wien Bridge Oscillator

by Omri
Tags: bridge, oscillator, wien
 P: 35 Hi all, I am doing a project on electronics about the Wien Bridge Oscillator. I learned about impedances and operational amplifiers and now I'm trying to understand the Wien Bridge circuit. I'm having some problems understanding it and I would be very happy to get some help. I still have not understood why oscillations occur in this circuit, what are the conditions for oscillations to occur, and how it works mathematically. I would be extremely thankful if anyone could instruct me or relate me to some good material about it. EDIT: to be more specific, I've been trying to understand the analysis here: http://en.wikipedia.org/wiki/Wien_bridge_oscillator If it gives some more specific reference... but I am totally willing to try other materials as well. Thanks a lot, Omri
 Sci Advisor P: 842 Check out this informative Powerpoint presentation: http://jeremya.com/engr/engr332/Wien...Oscillator.ppt
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 :-)

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