• Ankita Sharma

Wein Bridge Oscillator

An oscillator is an electronic circuit that converts direct current from a power supply to an alternating current producing repeated sinusoidal signals. Let us understand the basic principle behind oscillators - It employs an operational amplifier whose output terminal is fed back to the non-inverting terminal ( Positive Terminal ). There are many different types of electronic oscillators operating with the same basic principle.


In this article, we will learn the design and working principles of the Wein Bridge Oscillator.


What is Wein Bridge Oscillator?


Wein Bridge #Oscillator is an electronic oscillator producing sinusoidal waves operating under a large range of frequencies. It is based on a bridge circuit that was developed by Max Wein in 1891 for measuring impedances. The bridge comprises two capacitors and four resistors. So basically, It is a two-stage RC coupled filter having good stability at its resonant frequency.

Wein Bridge Oscillator Output
Wein Bridge Oscillator Output

How does a Wein Bridge Oscillator work?


The Wein #Bridge Oscillator uses positive feedback which consists of a series RC circuit connected in parallel with other RC having the same component values. This produces a phase delay or phase advance in the circuit depending upon the frequency. At the resonant frequency, the phase shift produced will be 0 degrees.


Wein Bridge Oscillator using OpAmp:


There are many ways to design a #Wein Bridge Oscillator, but here we will be designing the oscillator using #OPAMP ( Operational Amplifier ). So, let us understand the design of a Wein Bridge Oscillator -

Wein Bridge Oscillator using OpAmp
Wein Bridge Oscillator using OpAmp

The circuit consists of one OpAmp ( Operational Amplifier ), two capacitors, and four resistors forming two RC circuits. The resistors R3 and R4 are part of Opamp while the other two resistors R1 and R2 are part of the bridge circuit which forms the RC feedback network. Here, Opamp is used in the non-inverting configuration to provide positive feedback. Let us take a closer look at these two RC circuits-

RC circuit in Wein Bridge
RC circuit in Wein Bridge

R1 and C1 form series RC networks while the other pair i.e. R2 and C2 form parallel RC networks. The series RC circuit acts as High Pass Filter and the parallel RC circuit acts like Low Pass Filter.

  • At low frequencies, the series RC circuit will have low reactance. So, the High Pass Filter circuit acts as an open circuit i.e. it does not allow low frequencies to pass through the circuit. On the other hand, in the case of high frequencies, the reactance of the capacitor will be very low which in turn allows the high-frequency components to pass through them easily.

  • Low Pass Filter circuits ( Parallel RC ) do not allow high-frequency components to pass through the circuit.


What is the frequency of the Wein Bridge Oscillator?


Between the frequencies produced by high and low pass filters, one particular #frequency will exist at which the values of resistance and capacitance will be equal to each other producing maximum output voltage. This frequency is known as #Resonant Frequency which can be calculated using the following formula -

Frequency Calculation of Wein Bridge Oscillator
Frequency Calculation of Wein Bridge Oscillator

At Resonant Frequency-

  1. The phase shift of the circuit will be 0.

  2. The output voltage will be one-third of that of the input voltage.

  3. The Wein Bridge will be balanced.


Advantages and Disadvantages of Wein Bridge Oscillator:

Wein Bridge Oscillator is a wiser choice to produce sinusoidal output due to the following points -

  1. The circuit operation is quite easy.

  2. It produces low distortion and is very easy to tune.

  3. The Wein Bridge has good stability at its resonant frequency.

  4. It measures the unknown values of the components.

  5. The overall gain of the oscillator is high due to the presence of transistors.

The only disadvantage of a Wein Bridge Oscillators is that it cannot generate very high frequencies.


Conclusion :


This article gives an overview of a Wein Bridge Oscillator, its design, and working. The Wein Bridge oscillators are the most common bridge oscillators to measure audio frequencies ranging between 20Hz to 20KHz. They are very convenient and reliable and have a wide level of applications in the field of electronics.


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