Tutorial on Wien Bridge Oscillator Circuit And It’s Working

The Wien bridge oscillator is developed by Maxwien in the year 1981. The Wien bridge oscillator is based on the bridge circuit it consists of four resistors and two capacitors and it is used for the measurement of impedance. The huge amount of frequency is produced by the Wein bridge oscillator. The feedback circuit is used by the Wien bridge oscillator and the circuit consists of a series RC circuit which is connected to the parallel RC circuit. The components of the circuit have same values which give the phase delay and phase advance circuit with the help of frequency.

What is an Wien Bridge Oscillator?

The Wien bridge oscillator is an electronic oscillator and produces the sine waves. It is a two stage RC circuit amplifier circuit and it has high quality of resonant frequency, low distortion, and also in the tuning. Consider the very simple sine wave oscillator used by the RC circuit and place in the conventional LC circuit, construct the output of sinusoidal waveform is called as an Wien bridge oscillator. The Wien bridge oscillator is also called as a Wheatstone bridge circuit.

Wein Bridge Oscillator Circuit

The Wien bridge oscillator is used to find unknown values of components. In most of the cases this oscillator is used in the audios. The oscillators are designed simply, size is compressed and it has stable in frequency output. Hence the maximum output frequency of the Wien bridge oscillator is 1MHz and this frequency is from the phase shift oscillator. The total phase shift of the oscillator is from the 360° or 0°.

It is a two stage amplifier with RC bridge circuit and the circuit has the lead lag networks. The lags at the phase shift are increasing the frequency and the leads are decreasing the frequency. In additional by adding the Wien Bridge oscillator at a particular frequency it becomes sensitive. At this frequency the Wien Bridge is balance the phase shift of 0°. The following diagram shows the circuit diagram of the Wienbridge oscillator. The diagram shows R1 is series with the C1, R3, R4 and R2 are parallel with the C2 to from the four arms.

From the above diagram we can see the two transistors are used for the phase shift of 360°and also for the positive feedback. The negative feedback is connected to the circuit of the output with a range of frequencies. This has been taken through the R4 resistor to from the temperature sensitive lamp and the resistor is directly proportional to the increasing current. If the output of the amplitude is increased then the more current is offered more negative feedback.

Wien Bridge Oscillator Operation

The circuit is in the oscillation mode and the base current of the first transistor is changed randomly because it is due to the difference in voltage of DC supply. The base current is applied to the collector terminal of the first transistor and the phase shift is about the 180°. The output of the first transistor is given to the base terminal of the second transistor Q2 with the help of the capacitor C4. Further, this process is amplified and from the second transistor of collector terminal the phase reversed signal is collected.

The output signal is connected to the phase with the help of the first transistor to the base terminal. The input point of the bridge circuit is from the point A to point C the feedback of this circuit is the output signal at the second transistor. The feedback signal is given to the resistor R4 which gives the negative feedback. In this same way the feedback signal is given to the base bias resistor R4 and it produces the positive feedback signal.

By using the two capacitors C1 and C2 in this oscillator, it can behave continuous frequency variation. These capacitors are the air gang capacitors and we can also change the values of the frequency range of the oscillator.

Wein bridge oscillator using IC741

The following diagram shows the Wien bridge oscillator by using the IC74. This oscillator is a low frequency oscillator. The Wien bridge oscillator op-amp is used as the oscillator circuit and it is working like a non inverting amplifier. Hence the feedback network is got given to any phase shift. The circuit is observed like an Wien bridge on RC series network of one arm and the parallel RC network in for another arm. The resistor Ri and Rf are connected to the left two arms.

Applications of Wien Bridge Oscillators

• It is used to measure the audio frequency.
• Wien bridge oscillator designs the long range of frequencies
• It produces sine wave.

Advantages

• Distortion testing of power amplifier.
• It supplies the signals for testing filters.
• Excitation for AC Bridge.
• To fabricate pure tune.
• Long distance can be spanned by the resting beams.

Disadvantages

• The Wheatstone bridge is not used for the high resistance.
• The circuit needs the high no. of other components.
• The limited output frequency is obtained because the amplitude and the phase shift characters of the amplifier.

This article gives the information about the working of the Wien bridge oscillator and with circuit diagrams. I hope the information in the article is given basic knowledge about the Wien bridge oscillator. If you have any queries regarding this article or to implement an EEE final year projects, please comment in the below section. Here is the question for you, what are the functions of an Wein bride oscillator?

 Photo Credits:

• Wein Bridge Oscillator Circuit circuitstoday
• Wein bridge oscillator using IC741 elektroda