Editing Wien bridge oscillator (section)

{{Short description|Electric circuit that generates sine waves}}
[[File:Wien Bridge Oscillator.png|right|thumb|300px|In this version of the oscillator, Rb is a small incandescent lamp. Usually R1 = R2 = R and C1 = C2 = C. In normal operation, Rb self heats to the point where its resistance is Rf/2.]]

A '''Wien bridge oscillator''' is a type of [[electronic oscillator]] that generates [[sine wave]]s. It can generate a large range of [[frequencies]]. The oscillator is based on a [[bridge circuit]] originally developed by [[Max Wien]] in 1891 for the measurement of [[Electrical impedance|impedance]]s.<ref>{{Harvnb|Wien|1891}}</ref>
[[Wien bridge|The bridge]] comprises four [[resistor]]s and two [[capacitor]]s. The oscillator can also be viewed as a positive gain amplifier  combined with a [[bandpass filter]] that provides [[positive feedback]].  Automatic gain control, intentional non-linearity and incidental non-linearity limit the output amplitude in various implementations of the oscillator.

The circuit shown to the right depicts a once-common implementation of the oscillator, with automatic gain control using an incandescent lamp.  Under the condition that R<sub>1</sub>=R<sub>2</sub>=R and C<sub>1</sub>=C<sub>2</sub>=C, the frequency of oscillation is given by:

<math>f_{hz}=\frac{1}{2 \pi R C}</math>

and the condition of stable oscillation is given by

<math>R_b =  \frac {R_f} {2} </math>