Wien bridge oscillator is an

**audio frequency sine wave oscillator**of high stability and simplicity. Before that let us see**what is oscillator?**An oscillator is a circuit that produces periodic electric signals such as sine wave or square wave. The application of oscillator includes**sine wave generator**, local oscillator for synchronous receivers etc.Here we are discussing **wein bridge oscillator using 741 op amp IC**. It is a low frequency oscillator. The op-amp used in this oscillator circuit is working as non-inverting amplifier mode. Here the feedback network need not provide any phase shift. The circuit can be viewed as a wien bridge with a series RC network in one arm and parallel RC network in the adjoining arm. Resistors Ri and Rf are connected in the remaining two arms.

**Also see:**

## Wien bridge oscillator Circuit Diagram

## Components Required

- Resistors (1KΩ, 1.5KΩ x2)
- Potentiometer(4.7KΩ)
- Capacitor(0.1µF x2)
- 741 Op amp

## Output Waveform

## Working of Wein bridge Oscillator

- The feedback signal in this oscillator circuit is connected to the non-inverting input terminal so that the op-amp works as a non-inverting amplifier.

- The condition of zero phase shift around the circuit is achieved by balancing the bridge, zero phase shift is essential for sustained oscillations.

- The frequency of oscillation is the resonant frequency of the balanced bridge and is given by the expression
**fo = 1/2πRC**

- At resonant frequency ( ƒo), the inverting and non-inverting input voltages will be equal and “in-phase” so that the negative feedback signal will be cancelled out by the positive feedback causing the circuit to oscillate.

- From the analysis of the circuit, it can be seen that the feedback factor β= 1/3 at the frequency of oscillation. Therefore for sustained oscillation, the amplifier must have a gain of 3 so that the loop gain becomes unity.

- For an inverting amplifier the gain is set by the feedback resistor network Rf and Ri and is given as the ratio -Rf/Ri.

## Design

The required frequency of oscillation

**fo=1kHz**we have,

Take

**C=0.01µF**, then**R=**1.6kΩ (Use**1.5kΩ**standard)Gain of the amplifier section is given by,

Take

**Ri=1kΩ**, then**Rf**=2.2kΩ (Use**4.7kΩ Potentio meter**for fine corrections)## Wien bridge oscillator Frequency calculator

*R1 and C1 in the series arm and R2 C2 in parallel arm of feedback circuit*

Enter the Value of Resistor, R1 :in Ω

Enter the Value of Capacitor, C1 :in Farads

Enter the Value of Resistor, R2 :in Ω

Enter the Value of Capacitor, C2 :in Farads

Frequency of oscillation, F :in Hz