wien’s bridge oscillator using op-amp

WIEN’S BRIDGE OSCILLATOR USING

OP-AMPPresented By:

Gopal Chandra NepalDramzob

Gopal Chandra Nepal & Dramzob 2

Introduction• It generates output without giving input and

with no Phase Shift.

© Copyright Reserved


Introduction(cont…)• Uses two RC

networks connected to the positive terminal to form a frequency selective feedback network

• Causes Oscillations to Occur



Introduction

• Amplifies the signal with the two negative feedback resistors



Design Procedure• Two RC network

must have equal resistor and capacitor values.

• R1=R2=R• C1=C2=C• R4= 2*R3



Design Procedure

• When the Wien’s Bridge is balanced Gain must be 3.

• The gain can be found by:

3

43

R

RRGain

33

3*23

R

RRGain



Time

0s 0.2ms 0.4ms 0.6ms 0.8ms 1.0msV(R5:2)

-4.0V

0V

4.0V

G = 3

Time

0s 0.2ms 0.4ms 0.6ms 0.8ms 1.0msV(R5:2)

-4.0V

0V

4.0V

G = 2.9

Time

0s 100us 200us 300us 400us 500us 600usV(R5:2)

-20V

0V

20V

G = 3.05



Calculations• The values calculated are:• R1=R2=R = 10KΩ, • C1=C2=C= 0.22µF • R3 = 10KΩ. • R4 = 2*R3= 20KΩ

Hzk

fRC

34.7222.0*10**2

1

2

1

310

2010

K

KKGain



Circuit Diagram for Practical and Simulation



Steady Oscillation• Diode is added to the circuit diagram to make

the oscillation steady.• The Diode network keeps Gain around 3.• The Gain(G) is still equal to 3.



Simulation Output



Practical Output

Input Voltage

Output Voltage



Critical AnalysisSimulation Result• Simulation Frequency =

71.94Hz• Theoretical Frequency=

72.34Hz

Practical Result

%55.0

10034.72

94.7134.72(%)

Error

• Practical Frequency= 71.43Hz

• Theoretical Frequency= 72.34Hz

%26.1

10034.72

43.7134.72(%)

Error



Critical Analysis

• The error is caused due to:1. Use of non-ideal Op-Amp.2. The values of resistors were not exact.3. Due to resistance offered by connecting wires.



Precautions

• Precautions to be taken:1. While using diode keep gain slightly greater than

3.2. Check Op-Amp and other device for its

functioning.3. Check the connections.



Conclusion

• No input yet produces output.• Can output large range of frequencies.• The gain of amplifier must be around 3.• With proper configuration oscillation can go on

indefinitely.• Due to limitation of Op-Amp frequencies above

1MHz cannot be achieved.• There is no phase shift.© Copyright Reserved


References

• John. (2009, October) Circuits Today. [Online]. http://www.circuitstoday.com/wien-bridge-oscillator

• Wayne Storr. (200_) Electronics Tutorials. [Online]. http://www.electronics-tutorials.ws/oscillator/wien_bridge.html

• G. Ramakant, Op-Amps and Linear Integrated Circuits, 4th ed. India: Prentice Hall of India Pvt. Ltd., 2006.

• Robert Boylestead and L. Nashelsky, Electronics Devices and Circuit Theory, 6th ed. New Delhi, India: Prentice-Hall of India pvt Ltd, 2001.

• M. M. S. Anand, Electronic Instruments and Instrumentation Technology, 7th ed. New Delhi, India: PHI Learning Private Limited, 2001.

• D. D. Ronde.(May,2002), Wien’s Bridge Oscillator© Copyright Reserved


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wien’s bridge oscillator using op-amp

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