Wien Bridge Oscillator Wien Bridge Oscillator f o 10.28kHz j 1 U1 Vo C R C R R 3 R 4 Will oscillate at frequency f o 1 2π RC = Pick C 1nF R 1 2 π C f o 15.482 kΩ if 1 R 3 R 4 3 = Pick R 15kΩ which is a standard value Pick R 3 20kΩ R 4 10kΩ Page 170 of Lab Manual R 1 R 2 = R = C 1 C 2 = C = Transfer Function for Circuit shown in Fig 9.2.b Ts () V o V i = 1 R 3 R 4 sRC s 2 R 2 C 2 3sRC 1 = Second Order BPF Tf () 1 R 3 R 4 j2 π f R C j2 π f R C ( ) 2 3 j2 π f R C ( ) 1 1 10 3 1 10 4 1 10 5 20 10 0 100 50 0 50 100 20 log Tf () 180 π arg T f () ( ) f For the diode limiter network pick R A R B 30kΩ = V γ 0.7V = V o 5V = the peak value of the output sine wave. Solution with Eqn 9.8 yields R A 3.95kΩ = R B 26.05kΩ =
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Wien Bridge Oscillator
Wien Bridge Oscillatorfo 10.28kHz j 1
U1 Vo
C R
CR
R3
R4
Will oscillate at frequency
fo1
2π RC= Pick C 1nF
R1
2 π C fo15.482kΩ
if
1R3
R4 3= Pick R 15kΩ
which is a standard value
Pick R3 20kΩ R4 10kΩ
Page 170 of Lab Manual
R1 R2= R= C1 C2= C=
Transfer Function for Circuit shown in Fig 9.2.b
T s( )Vo
Vi= 1
R3
R4
sRC
s2
R2
C2
3sRC 1= Second Order BPF
T f( ) 1R3
R4
j 2 π f R C
j 2 π f R C( )2
3 j 2 π f R C( ) 1
1 103 1 10
4 1 105
20
10
0
100
50
0
50
100
20 log T f( ) 180
πarg T f( )( )
fFor the diode limiter network pick RA RB 30kΩ= Vγ 0.7V=
Vo 5V= the peak value of the output sine wave. Solution with Eqn 9.8 yields
RA 3.95kΩ= RB 26.05kΩ=
0
0
1
1
2
2
3
3
4
4
5
5
6
6
7
7
8
8
A A
B B
C C
D D
E E
F F
G G
VCC15V
VEE-15V
U1
R1
15kΩ
C1
1nF
C21nF
RF
22kΩ
R310kΩ
Title:
Document N:
Date: Sheet of
Revision:Size:
Wien
0001
2012-06-20 1 1
1.0A
Set ICs to Zero and use small time steps compared to a period.
Use Virtual Op Amp 5 Terminals
This is Multisim
R215kΩ
out
VCC15V
VEE-15V
U2
R4
15kΩ
C3
1nF
C41nF
R5
22kΩ
R610kΩ
R715kΩ
R83.95kΩ
R93.95kΩ
R10
26.05kΩ
R11
26.05kΩ
VEE-15V
out_3
VCC15V
D1
D2
WienPrinting Time:Wednesday, June 20, 2012, 8:39:16 PM
V(out)
Transient Analysis
Time (s)
0.00 1.50m250.00µ 1.25m500.00µ 1.00m750.00µ
Voltage (V)
-20
20
-10
10
0
(925.0564µ, 4.8770)
(1.0198m, 9.1726)
No Diode Limiter All Initial Conditions set to zero
It Clips at the dc power supply voltages. Highly undesirable.
Frequency of Oscillation
10.5548026kHz
WienPrinting Time:Wednesday, June 20, 2012, 8:43:31 PM
V(out_3)
Transient Analysis
Time (s)
0.00 1.50m250.00µ 1.25m500.00µ 1.00m750.00µ
Voltage (V)
-7.5
7.5
-5.0
5.0
-2.5
2.5
0.0
(1.0167m, 5.0859)
Diode Limiter Peak Output
5.0859 V
WienPrinting Time:Wednesday, June 20, 2012, 8:49:20 PM
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9
10
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13
14
15
16
17
18
Fourier analysis for V(out_3):
DC component: -0.031584
No. Harmonics: 9
THD: 6.76763 %
Grid size: 256
Interpolation Degree: 1
Harmonic Frequency Magnitude Phase Norm. Mag Norm. Phase
Procedure Time Completed Date Completed Verification (Must demonstrate
circuit)
Points Possible
Points Received
3. Wein Bridge 25
4. Phase Shift 25
5. Quadrature 25
Enter your critical frequency below:
fcrit
To be permitted to complete the experiment during the open lab hours, you must complete at least three procedures during your scheduled lab period or spend your entire scheduled lab session attempting to do so. A signature below by your lab instructor, Dr. Brewer, or Dr. Robinson permits you to attend the open lab hours to complete the experiment and receive full credit on the report. Without this signature, you may use the open lab to perform the experiment at a 50% penalty.
Make sure you have made all required measurements before requesting a check‐off. For all check‐offs, you must demonstrate the circuit or measurement to a lab instructor. All screen captures must have a time/date stamp.
Wein bridge and phase shift oscillators Scope capture showing open loop input and output waveforms in phase. Display Vpp and frequency
measurements. Scope capture showing closed loop output waveform. Display Vpp and frequency measurements. Scope capture showing closed loop output waveform with limiter. Display Vpp and frequency
measurements. Comparison of the measured frequency of oscillation to the design value. Adjust the circuit component
values if the measured value is not within 10% of the design value. Quadrature oscillator Scope capture showing both output waveforms. Display Vpp, frequency, and phase measurements. Scope capture of XY plot. Comparison of the measured frequency of oscillation to the design value. Adjust the circuit component
values if the measured value is not within 10% of the design value.