Wein Bridge Oscillator.
Aim: To study of wein bridge oscillator & to perform the experiment.
Apparatus:
Sr. No. Items Reqd.no. Range Remark
01. Resistor
02. Capacitor
03. CRO.
Theory: The experiment of wein bridge oscillator . Because of its simplicity and stability, wein bridge oscillator is audio frequency oscillator.
The figure shows the Wein Bridge oscillator in which the amplifier input terminals and the out put terminal. The bridge has a series RC network in one arm and a parallel RC network in the adjoining arm. In the remaining two arms of the bridge, Resistor R & Rf are connected.
The phase angle criterion for oscillation is that the total phase shift around the circuit must be 0`. This condition occurs only when the bridge is balanced, that is, at resonance. The frequency of oscillation f0 is exactly the resonant frequency of the balanced wein bridge & is given by,
F0 = = 0.159/RC. ___________(1).
Assuming that the resistors are equal in value and capacitors are equal in value in the reactive lag of wein bridge. At this frequency the gain required for subs tined oscillation is given by,
Av = 1/B = 3. that is,
1+Rf/Ri = 3. Or Rf = 2 Ri____________(2).
For the derivation of equation (1) & (2), refer to appendix C. The wein bridge oscillator is designed using equation (1) & (2).
PROCEDURE:
� Connection are made as per diagram.
� CRO is connected to the o/p terminal of the circuit.
� Supply is given at i/p terminal of the circuit.
� In both arm of R-C.
(1) R1 is constant or same value.
(2) C1 is connected in series & parallel with R1 & take reading.
(3) C2 is connected in series & parallel with R1 & take reading.
(4) C3 is connected in series & parallel with R1 & take reading.
� And the similar process for R2 & R3 are also constant & apply same process for above. Similar process for C1, C2,C3 from above, note reading.
OBSERVATION TABLE :
Sr. No. Combination
R-C Time
Period T F=1/T.
Measured. Calculated
Frequency. Observed
Frequency.Fo.
CONCLUSION:-
The wein bridge oscillator is the standard oscillator circuit for low to moderate frequencies, in the range of 5Hz above 1MHz. It is almost always used in commercial audio generators & is usually preferred for other low frequency application. It produces an almost per fact sine wave.