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23 Jul, 2024 @ 01:30 PM

Introduction

In this blog, we will thoroughly discuss one of the topics of Circuit theory that will circulate a signal. Do you know how we can oscillate the current flowing through a circuit? If not, you are at the right place. This blog will thoroughly explain all the concepts related to it. In the end, we will also discuss the advantages and disadvantages of the Wien bridge oscillator.

This blog will discuss the topic of the Wien Bridge Oscillator. Let's start with the definition.

What is a Wien Bridge Oscillator?

Wein bridge oscillator is a type of oscillator that helps to make the sine waves as an output. We can use the Wein bridge oscillator to generate a huge range of frequencies. This complete system is based on the bridge circuit, and the bridge is formed using two capacitors and four resistors.

The name of the Wien bridge oscillator is given on the name of Max Karl Wien, who was one of the great physicists. The Wien bridge oscillator was developed in 1890.

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Wein Bridge Oscillator Circuit Diagram

Let's discuss the construction of the Wein bridge oscillator.

The Wein bridge oscillator is a two-stage amplifier with a resistor-capacitor (RC) circuit.

In this bridge, the capacitor C1 is series with the resistors R1 and R3, and the resistor R2 is parallel with the capacitor C2.

There is a tungsten lamp (Lp) that is parallel with the resistor R1.

We are using the resistor Lp and R3 as a stabilizer. This will help to maintain the amplitude of the output.

We have used two transistors, Q1 and Q2. Both Q1 and Q2 make a phase of 360 degrees.

The first transistor, Q1, acts as an amplifier and an oscillator. On the other hand, the transistor, Q2, acts as an inverter.

In this diagram, the transistor, Q1, is getting positive feedback from the circuit having series and parallel connections., i.e., R1C1 and C2R2.

The transistor, Q2, is getting negative feedback from the voltage divider to the input.

Wien Bridge Oscillator Frequency

Now, the frequency of oscillations by the C1R1 and C2R2, which are in series and parallel connection of the bridge, is:

f = 1 / 2π√ R1C1R2C2

If the value of R1 = R2 = R and C1 = C2 = C, then:

f = 1 / 2πRC

Let's now discuss the series and parallel connections in the bridge.

A connection is in series when the same amount of current flows through the given resistors. The general formula of the series is as follows:

R = R1 + R2 + ….. + Rn

where R1, R2...Rn is the resistors connected in the circuit.

A connection is in parallel when the voltage is the same across all the resistors. The general formula of parallel connection is as follows:

1/R = 1/R1 + 1/R2 + ..... + 1/Rn

where R1, R2...Rn is the resistors connected in the circuit.

Impedance

A bridge circuit is used to measure impedances in the above diagram. Impedance occurs due to the reactance and resistance. In simpler words, Impedance is the measure of the nature of opposition of the AC current. This is created due to the inductance and the capacitance. It is denoted by the letter Z.

According to the circuit diagram of the Wien Bridge Oscillator, the impedance of the series connection can be:

Z = R1 + XC1

where Z is impedance, R1 is a resistor, and C1 is a capacitor of the bridge in the Wien Bridge Oscillator. Here X is the reactance.

The impedance for parallel connection in the bridge is as follows:

1/Z = 1/R2 + 1/C2

where R2 and C2 are the resistor and the capacitor.

Working of Wien Bridge Oscillator

The working of the Wien Bridge Oscillator is as follows:

When the current passes through the Vcc, the bridge circuits start oscillating using the capacitor and resistor.

There is a phase shift of 360 degrees to maintain proper positive feedback using the two transistors.

The negative feedback ensures the constant output in the circuit. The lamp (Lp) and the resister (R3) help the circuit to achieve negative feedback.

The Wien bridge oscillator is a type of oscillator that is based on the sine waves. The first transistor rotates the input sine wave to 180 degrees, making it a cosine wave. But the second transistor again rotates the cosine wave to 180 degrees and makes it a sine wave to return as an output.

While circulation of feedback, if the current increases in the bridge, it means the negative feedback is more. There is a tungsten lamp along with resistors to maintain the overflow of the current. Hence we will get the original value through the output.

Applications of Wien Bridge Oscillators

Below are some of the key applications of Wien Bridge Oscillators:

Frequency generation in audio and RF circuits

Signal testing and calibration

Function generators for sine wave output

Phase-locked loop (PLL) circuits

Medical instrumentation

Audio equipment like tone generators

Advantages of Wien Bridge Oscillator

We have now covered almost everything. Let us now discuss some advantages of the Wien bridge oscillator.

The Wien bridge oscillator provides the signals for testing filters.

It delivers a high current due to the presence of two transistors that amplifies the current two times faster.

The frequency stability of the Wien bridge oscillator is good.

We can change the frequency of oscillation anytime using the potentiometer.

The sine wave produced by the Wien bridge oscillator is good and less distorted.

Disadvantages of Wien Bridge Oscillator

If there are pros of something, there must be some cons as well. Let us discuss some cons of using the Wien bridge oscillator.

The Wien bridge oscillator needs a high number of tools which cannot be available all the time.

The circuit is complex due to the two transistors and many other parts.

The Wien bridge oscillator cannot create very high frequencies.

Frequently Asked Questions

What is the Wien bridge oscillator?

A Wien Bridge Oscillator is a type of electronic oscillator that generates a sinusoidal waveform, typically used in audio and RF applications due to its simplicity and frequency stability.

What is the working principle of Wein bridge oscillator?

The Wien Bridge Oscillator operates based on the principle of feedback and resonance. It employs a bridge network with resistors and capacitors to achieve positive feedback and sustain oscillations.

What is the bridge oscillator used for?

Wien Bridge Oscillators find use in signal generation, audio equipment, phase-locked loops, and medical instruments due to their ability to produce stable sinusoidal waveforms.

What is the variable frequency of the Wien bridge oscillator?

The frequency of a Wien Bridge Oscillator is variable and can be adjusted by altering the resistance or capacitance values in the bridge network, making it versatile for different frequency requirements.

What is a Wien bridge oscillator and phase shift oscillator?

An electronic oscillator that generates sinusoidal output is called a Wien bridge oscillator. To determine the oscillation frequency, a bridge network consisting of resistors and capacitors is commonly employed. A phase shift oscillator uses a sequence of RC networks to produce phase shifts in oscillations.

What is the main function of Phase Shift Oscillator?

A Phase Shift Oscillator's primary job is to produce sinusoidal output signals at a given frequency. It accomplishes this by creating phase changes through a sequence of RC networks, which leads to positive feedback and long-lasting oscillations at the intended frequency.

Conclusion

This article discusses the topic of the Wien bridge oscillator in detail. We have seen the definition, circuit diagram, working, sample numerical, and pros and cons of the Wien bridge oscillator.

We hope this blog has helped you enhance your knowledge of the Wien bridge oscillator. If you want to learn more, then check out our articles.