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Wednesday, October 5, 2011

WEIN BRIDGE OSCILLATOR Electronic devices and circuits lab manual


WEIN BRIDGE OSCILLATOR
AIM: To study and calculate frequency of. Wein Bridge Oscillator.

APPARATUS:
Transistor                (BC 107)           2 No
Resistors                 10K               4 No
                                               1 K               3 No
                                               2.2 K            2 No
                                              33 K             
                                              6.8 K           
Capacitors                          10               2 No
                                              100             
                                              0.01            2 No
RPS                         (0 – 30 V)        
Potentiometer                                              
Bread Boar
CRO
Connecting wires
         
CIRCUITDIAGRAM: 


THEORY:
                      The wein bridge oscillator is a standard circuit for generating low frequencies in the range of 10 Hz to about 1MHz.The method used for getting +ve feedback in wein bridge oscillator  is to use two stages of  an   RC-coupled amplifier. Since one stage of the RC-coupled amplifier introduces a phase shift of 180 deg, two stages will introduces a phase shift of 360 deg. At the frequency of oscillations f the +ve feedback network shown in fig makes the input & output in the phase. The frequency of oscillations is given as
                                             f =1/2π√R1C1R2C2
 In addition to the positive feedback

PROCEDURE:
1.    Connections are made as per the circuit diagram
2.    Feed the output of the oscillator to a C.R.O by making adjustments in the   Potentiometer connected in the +ve feedback loop, try to obtain a stable sine  Wave.
3.    Measure the time period of the waveform obtained on CRO. & calculate the    Frequency of oscillations.
4.    Repeat the procedure for different values of capacitance.

OBSERVATION:
Given R=10kΩ, C=0.01μF
fT =  1/ 2pRC
fP =  =
Amplitude,V0 =
MODEL WAVE FORM:


RESULT:
        The frequency of the wein bridge oscillator is calculated and is verified  

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