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.
Wien bridge oscillator Circuit Diagram
- Resistors (1KΩ, 1.5KΩ x2)
- Capacitor(0.1µF x2)
- 741 Op amp
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.
Wien bridge oscillator Frequency calculator
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