GROUP MEMBERS

☺ISMAIL SHAHID SHAHKAR(12)

☺FAIZ UL ISLAM KHAKSAR(22)

☺HUSSAIN MUHAMMAD IRSHAD(50)

*TOPIC*

☺WIEN BRIDGE OSCILLATOR

*HISTORICAL BACKGROUND*

☺A Wien bridge oscillator is a type of electronic oscillator that generates sine waves.

☺It can generate a large range of frequencies.

☺The circuit is based on an electrical network originally developed by Max Wien in 1891.

☺ Wien did not have a means of developing electronic gain so a workable oscillator could not be realized.

☺The modern circuit is derived from William Hewlett's 1939 Stanford University master's degree thesis.

☺Hewlett, along with David Packard co-founded Hewlett-Packard.

☺Their first product was the HP200A, a precision sine wave oscillator based on the Wien bridge. The 200A was one of the first instruments to produce such low distortion.

*EXPLANATION*☺It is the most popular type of oscillators

used in audio frequency ranges (20-20KHz).

☺These are simple in design, compact in size, remarkably stable in its frequency output.

☺The maximum frequency output of a typical W.B. oscillator is about 1MHz.

☺Wien bridge oscillator is infact a phase-shift oscillator which produces a total phase-shift of 360º or 0º.

*CIRCUIT*

*DIAGRAM*

WIEN BRIDGE OSCILLATOR CIRCUIT IMPLEMENTED ON P-SPICE

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*MATHEMATICAL*

* DERIVATION*

From the ckt it is obvious that the bridge will be balanced only when;

23 4 1

2 2 1

3 2 4 1 2 21

43 2 4 1 2 2

1

4 4 2 23 2 4 1 4 1 2 2

1 1

4 2 23 2 4 1

1

1

1

1

0

R jR R R

j R C C

jR R R R j R C

C

R jR R R R j R C

C

R j R R CR R R R R R j R C

C C

R R CR R R R

C

4 2 23 2 4 1

1

32 1

1 4 2

44 1 2 2

1

24 1 2 2 1 4

24 1 2 2 1 4

0

0

R R CR R R R

C

RC R

C R R

RR R R C

C

R R R C C R

R R R C C R

2

1 2 1 2

1 2 1 2

1 2

1 2

1

1

2

1

2

R R C C

fR R C C

C C C

R R R

fRC

*2nD METHOD*

1

2

1

2

1

2

c

c

c

XfC

fX C

X R

fRC

*LEAD LAG CIRCUIT*

*ADVANTAGES*☺Provides a stable low distortion

sinusoidal output over a wide range of frequency.

☺The frequency range can be selected simply by using decade resistance boxes.

☺The frequency of oscillation can be easily varied by varying capacitances C1 and C2 simultaneously.

☺The overall gain is high because of two transistors.

*DISADVANTAGES*

☺The circuit needs two transistors and a large number of other components.

☺The maximum frequency output is limited because of amplitude and the phase-shift characteristics of amplifier.

*PRACTICAL IMPLEMENTATION*

*THANX*

(THE END)