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The Wien Bridge Oscillator comprises an Op-Amp, four resistors and two capacitors. The oscillator can also be viewed as a positive gain amplifier combined with a bandpass filter that provides positive feedback. At the resonant frequency, the reactance of the series R2–C2 arm will be an exact multiple of the shunt R1–C1 arm. If the two R3 and R4 arms are adjusted to the same ratio, then the bridge is balanced. These conditions can be written as:

<math>\omega^2 = \frac {1}{R_1 R_2 C_1 C_2}</math>

and

<math> \frac {C_1}{C_2} = \frac {R_4}{R_3} - \frac {R_2}{R_1}</math>

This can be further simplified by setting R1 = R2 = R and C1 = C2 = C. In that case, setting R4 = 2 R3 will satisfy the above conditions and will lead to the following simple equation for the oscillation frequency:

<math>f_o = \frac {1}{2 \pi RC}</math>

For this project, you will initially choose R1 = R2 = 10k, R3 = 10k, R3 = 2 R3 = 20k, and C1 = C3 = 100pF. Place and connect all the parts as shown in the above figure. Place a voltage probe marker at the output of the Op-Amp. The oscillation frequency of this circuit must be f_o = 1 / (2&pi; . 1e+4 . 1e-9) = 15.9kHz.

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=== Analyzing the Wien Bridge Oscillator and Explaining Its Behavior ===