The Wien Bridge Oscillator is a type of electronic oscillator that generates sinusoidal signals at a specific frequency. It was first invented by Max Wien in 1891 and has been widely used in various applications, such as audio frequency generation and frequency synthesis.
The basic components of a Wien Bridge Oscillator are:
Operational Amplifier (OpAmp): The heart of the oscillator, an OpAmp is a highgain voltage amplifier with both inverting and noninverting inputs.
Resistors (R): Two resistors with equal resistance, usually denoted as R1 and R2, are used in the feedback network of the OpAmp.
Capacitors (C): Two capacitors, usually denoted as C1 and C2, are used in the feedback network as well. C1 and C2 also have equal capacitance.
The circuit diagram of the Wien Bridge Oscillator looks like this:
scss
Copy code
+Vcc

R1

+ C1 o C2 +
 
+ R2 o R2 o 
   
   
   
 GND GND 
+ooo (Output)
The principle behind the operation of the Wien Bridge Oscillator lies in the feedback network and the inherent phase shift characteristics of the RC elements.
Here's a stepbystep explanation of the operation:
Initial State: Let's assume the OpAmp is operating in a linear region, and the output is initially at a moderate voltage level (close to 0V).
Feedback Mechanism: As the OpAmp amplifies the voltage difference between its inverting and noninverting inputs, the signal is fed back to the inverting input through the RC network (R2C2). The feedback network determines the frequency of oscillation.
Phase Shift: The key to oscillation is the phase shift provided by the feedback network. At the oscillation frequency, the total phase shift around the feedback loop becomes 360 degrees (or 0 degrees if considering only the phase difference). This means the signal at the inverting input is inphase with the signal at the noninverting input.
Frequency Determination: The frequency of oscillation is determined by the values of R1, R2, C1, and C2. The formula for the oscillation frequency is:
f = 1 / (2 * π * R * C)
where R is the resistance of R1 and R2 (since they are equal) and C is the capacitance of C1 and C2 (since they are equal).
Amplitude Stabilization: The OpAmp's gain (A) is ideally set to 3 (29.4 dB) in a Wien Bridge Oscillator. At this gain, the output amplitude stabilizes, and the oscillator generates a nearly sinusoidal waveform.
StartUp: Any small noise or disturbance in the circuit can initiate the oscillation process. The feedback and phase shift conditions are met, and the oscillation builds up until it reaches a steady state.
In summary, a Wien Bridge Oscillator generates sinusoidal signals through positive feedback and careful control of the phase shift in the feedback network. It is a simple and reliable oscillator design widely used in signal generation applications, where a stable and precise sinusoidal waveform is required, such as in audio frequency applications and frequency calibration devices.