Wien Bridge Oscillator | Analog and Digital Electronics - Electrical Engineering (EE) PDF Download

Wien Bridge Oscillator

                                  Wien Bridge Oscillator | Analog and Digital Electronics - Electrical Engineering (EE)

 

The output of the operational amplifier is fed back to both the inputs of the amplifier. One part of the feedback   signal   is conn ected to   the inverting input terminal (negative feedback) via the resistor divider network of R1 and R2 which allows the amplifiers voltage gain to be adjusted within narrow limits.

The other part is fed back to the non- inverting input terminal (positive feedback) via the RC Wien Bridge network. The RC network is connected in  the positive feedback path of the amplifier and has zero phase shift a just one frequency. Then at the selected resonant frequency, ( ƒr ) the voltages applied to the inverting and non- inverting inputs will be equal and "in- phase" so the positive feedback will cancel out the negative feedback signal causing the circuit to oscillate.

Also the voltage gain of the amplifier circuit MUST be equal to three "Gain =3" for oscillations to start. This value is set by the feedback resistor network, R1 and R2 for an inverting amplifier and is given as the ratio - R1/R2.

 Also, due to the open- loop gain limitations of operational amplifiers, frequencies above 1MHz are unachievable without the use of special high frequenc y op- amps. Then for oscillations to occur in a Wien Bridge Oscillator circuit the following conditions must apply.

1. With no input signal the Wien Bridge Oscillator produces output oscillations.

2. The Wien Bridge Oscillator can produce a large range of frequencies.

3. The Voltage gain of the amplifier must be at least 3.

4. The network can be used with a Non- inverting amplifier.

5. The input resistance of the amplifier must be high compared to R so that the RC network is not overloaded and alter the required conditions.

6. The output resistance of the amplifier must be low so that the effect of external loading is minimised.
7. Some method of stabilizing the amplitude of the oscillations must be provided because if the voltage gain of the amplifier is too small the desired oscillation will decay and stop and if it is too large the output amplitude rises to the value of the supply rails, which saturates the op- amp and causes the output waveform to become distorted.

8. With amplitude stabilisation in the form of feedback diodes, oscillations from the oscillator can go on indefinitely

The document Wien Bridge Oscillator | Analog and Digital Electronics - Electrical Engineering (EE) is a part of the Electrical Engineering (EE) Course Analog and Digital Electronics.
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FAQs on Wien Bridge Oscillator - Analog and Digital Electronics - Electrical Engineering (EE)

1. What is a Wien Bridge Oscillator?
Ans. A Wien Bridge Oscillator is an electronic circuit that generates a sinusoidal waveform at its output. It is commonly used in audio and RF applications for its simplicity and stability.
2. How does a Wien Bridge Oscillator work?
Ans. The Wien Bridge Oscillator consists of a feedback network with a combination of resistors and capacitors. The network is designed such that it produces a phase shift of 180 degrees at a specific frequency, resulting in positive feedback and sustained oscillation.
3. What are the key components of a Wien Bridge Oscillator?
Ans. The key components of a Wien Bridge Oscillator include a non-inverting amplifier, a resistor-capacitor network, and a frequency-selective feedback network. These components work together to create and sustain the oscillations at the desired frequency.
4. How can the frequency of a Wien Bridge Oscillator be adjusted?
Ans. The frequency of a Wien Bridge Oscillator can be adjusted by varying the values of the resistors and capacitors in the feedback network. By changing these values, the phase shift at the desired frequency can be achieved, allowing for frequency adjustment.
5. What are the advantages of using a Wien Bridge Oscillator?
Ans. The advantages of using a Wien Bridge Oscillator include its simplicity, stability, and ability to generate a pure sinusoidal waveform. It is also relatively low-cost and can be easily implemented with common electronic components. Additionally, it provides good frequency stability over a wide range of temperatures and component variations.
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