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

my circuit is not working dnt know why

and not even displaying the output in software’s proteus etc

Don,t worry!

Once again just go through the circuit that you have designed and check out the values of all the components.

Compare it with the standard reference material. Cross check the calculations!

Thanks

Ramesh Parmar

L.E.College, Morbi

Gujarat- India

You need to correct your circuit diagram, which gives the impression that the output merely goes out from pin 6 to the speaker (or amplifier.) In actuality, it needs to be fed back into both the inverting and non-inverting inputs. Either put a node (dot) or connect the inverting and non-inverting lines in different places to make this explicit.

Tru Dat

the circuit above confirmed works and by tune the potentio meter i got 6.5Khz with no modification of the brief circuit.

Thank you.

i satisfied

Hi, I have revised your calculated values, and with these element values, the frecuency is around of 10 KHz: fo=1/(2×3,14×1,5e3x0,01e-6)=10,6 KHz, not 1KHz.

why we use op amp instead of transistor

Opamps provide more gain than transistor. So more amplification can be obtained by fewer stages.