manual

1. PHASE SHIFT AND WEIN BRIDGE OSCILLATOR
AIM:
1. To design, construct and to obtain the oscillations of Wein Bridge
oscillator.
APPARATUS REQUIRED: COMPONENTS REQUIRED:
S.
No.
Apparatus Range Qty
1 RPS (0-30)V 1
2 CRO 1
3 DCB 3
4 Bread board 1
5
Connecting
wires
THEORY:
WEIN BRIDGE OSCILLATOR:
The circuit diagram of Wein Bridge oscillator is essentially a two-stage
amplifier with an RC bridge circuit. RC bridge circuit (Wein Bridge) is a Lead Lag
network. The Phase shift across the network lags with increasing frequency and
leads with decreasing frequency. By adding Wein bridge feedback network the
oscillator becomes sensitive to a signal of only one particular frequency. This
particular frequency is that at which Wein Bridge is balanced and for which the
phase shift is 0°.If Wein Bridge feedback network is not employed and output of
transistor T2 is fed back to transistor T1 for providing regeneration required for
producing oscillations, the transistor T1 will amplify signals over a wide range of
frequencies and thus direct coupling would result in poor frequency stability.
Thus by employing Wein Bridge feedback network frequency stability is
increased.
The circuit is set in to oscillation by any random change in base current of
transistor T1 , that may be due to noise inherent in the transistor or variation in

2. voltage of DC supply. This variation in base current is amplified in collector circuit
of transistor T1 but with a phase shift of 180 °. The output of transistor T1 is fed to
the base of second transistor T2 through capacitor C4 .Now a still further amplified
and twice phase reversed signal appears at the collector of the transistor
T2.Having been inverted twice , the output signal will be in phase with the signal
Design:
WEIN BRIDGE OSCILLATOR:
VOUT2
20KΩ
200KΩ
500Ω
2N 2222 Q1
+12V
0.02uF
0.0047uF
2.2K
Ω
Q2
4.7KΩ15KΩ
0.0047uF
4.7KΩ
2N 2222
2.2K
Ω
1K
Ω
3.6K
Ω
WEIN BRIDGE OSCILLATOR:
1. Connections are made as per the circuit diagram (ii) .
2. Collector voltage signal of transistor T2 is monitored in the CRO.

3. 3. The frequency is calculated from the waveform obtained.
4. The graphs are plotted for VCE2 Vs Time .
TABULAR COLUMN:
WEIN BRIDGE OSCILLATOR:
COLLECTOR
VOLTAGE
(VCE) VOLTS
COLLECTOR
VOLTAGE
(VCE) VOLTS
Amplitude
Time
Period
MODEL CALCULATION:
WEIN BRIDGE OSCILLATOR:
T =
f = 1 / T =

4. MODEL GRAPH:
PHASE SHIFT OSCILLATOR
WEIN BRIDGE OSCILLATOR:
RESULT:
1. Thus the RC Phase shift oscillator is designed, constructed and its
oscillations about _____ KHz .is obtained.
2. Thus the Wein Bridge oscillator is designed, constructed and its
oscillations about _____ KHz .is obtained.
VCE
(Volts)
t (ms)
VBE
(Volts)
t (ms)
VCE
(Volts)
t (ms)