Wien bridge oscillator is a combination of op-amp as an amplifier and a Wien bridge network in feedback path. Wien bridge network is made up of four arms. In one arm there is series RC network. In the adjoining arm there is parallel RC network. These two arms are called frequency sensitive arms. Rest two arms consist of two fixed value resistor. This type of network is called lead-lag network because at low frequency it acts like a lead and at high frequency it act like lag.
The circuit presented here demonstrates how to generate Audible Frequency from an AVR Microcontroller. The output of Microcontroller is always digital so to generate audible sound at the outset first it needs to be converted into Analog. A DAC (Digital to Analog Converter) is used for this purpose. Microcontroller generates sine wave of Audible Frequency using DAC. This sine wave is further given to Audio Amplifier that drives speaker. Microcontroller generates sine wave of fix frequency continuously. So we can hear an audible tone of fix frequency
The circuit presented here in this project generates two different types of wave forms using two OP-AMP chips LM741. It generates square wave and triangular wave. These waveforms can be applied as input to any other circuit to test their operation. Like square wave can be applied to any digital device as pulse input and triangular wave can be given to sweep frequency generator that will generate different frequencies (frequency sweep from min to max) as positive (or negative) ramp of triangular wave is applied.