1 oscillator bollen. 2 agenda bollen what is oscillation analog oscillation wien bridge oscillator...
TRANSCRIPT
1
OSCILLATOR
Bollen
2
AGENDA
Bollen
What is oscillation Analog oscillationWIEN bridge oscillatorHigh pass and low pass combinedRelaxatin oscillatorRC circuit 15k and 10 nFVoltage diviver 15k and 15kComparatorSignals and outputChargeDischarge
Frequency = 1 / total timeVariationaSummary
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What is oscillation
Bollen
Circuit powered by Vcc and Vee
No input signal, only output signal
Wienbridge Oscillator; output signal is sine wave
(used for making radio frequencies)
Relaxation Oscillatoer; output signal is a “digital” block signal
(used for clock or count circuits)
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What is analog oscillationWIEN bridge oscillator
Bollen
Barkhausen criterium:
Loopgain = 1
Total phase = 0 or 360
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WIEN bridge oscillator
Bollen
Oscillator for
High frequency
Sine signals
It uses 2 filters;
High pass and low pass
For one frequency the phase = 0 degrees !!!!
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High Pass and Low Pass combinated
Bollen
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WIEN bridge oscillator
Bollen
Barkhausen criterium:
Loopgain = 1
Total phase = 0 or 360
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WIEN bridge oscillator
Bollen
21
1 22 1
1
1 1
RjwCUout
Uin R RjwC jwC
2 2
21 2 2 1 2 2 1 2 1 2 1
wR CUout
Uin w RC R C R C j w R R C C
After “short” mathematics;
21 2 1 2 1 2 1 21 0
1
2oscillation
w R R C C for R R R and C C C
fRC
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WIEN bridge oscillator
Bollen
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21
21
12
21
21
1 2 22 1 1
1
1
11
1
1
1 1 1
RjwC
RjwCUout
Uin RjwC
RjwC R
jwC
RjwC
R R RjwC jwC jwC
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WIEN bridge oscillator
Bollen
21
1 2 21 2 2
1 2 1 2 1
1
1
RjwCUout
R R RUin R RjwC jwC w C C jwC
2
11 2 1 1 2 2
2 2
1RUoutCUin jwR R C R R j RC wC
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WIEN bridge oscillator
Bollen
2
11 2 1 1 2 2
2 2
1RUoutCUin jwR R C R R j RC wC
2 2
21 2 2 1 2 2 1 2 1 2 1
wR CUout
Uin w RC R C R C j w R R C C
For phase = o degrees; imaginair part = 0
21 2 1 2 1 2 1 21 0
1
2oscillation
w R R C C for R R R and C C C
fRC
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WIEN bridge oscillator
Bollen
2 2
21 2 2 1 2 2 1 2 1 2 1
wR CUout
Uin w RC R C R C j w R R C C
For R1 = R2 = R
And C1 = C2 = C
At oscillation
IM = 0
Au = 1/3
so amplificaton should be +3
Rf = 2 Rs
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WIEN bridge oscillator
Bollen
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What is “digital” oscillationRelaxation oscillator
Bollen
RC-circuit 15k and 10nF;
charge / discharge
Voltage divider 15k and 15k;
high treshold / low treshold
Comparator
Output:
block Vcc / Vee
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RC-circuit 15k and 10nF
Bollen
Vin = Vcc = +12 for charge
And = Vee = -12 for discharge
t
RCc final final initialV V V V e
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Voltage divider 15k and 15k
Bollen
Vin = +12 volt = opamp output high or
Vin = - 12 volt = opamp output low
V treshold up = +6 V for +12 opamp output
V treshold low = -6 V for – 12 opamp output
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Comparator
Bollen
Inverting input;
Uc, capacitor voltage
Non inverting input;
Treshold voltage, high (+6 Volt)
or low (-6 volt)
Output: 0outV A V V
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Signals and output
Bollen
Blue = output signal (+12 Volt or – 12 Volt)
Green = treshold signal (+6 Volt of – 6 Volt)
Red = capacitor signal
t
RCc final final initialV V V V e
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Charge
Bollen
R = 15 k
C = 10 nF
Vfinal = +12 V
Vinitial = -6 V
Switch at Vc = +6 Volt
15 .10
arg
6
6
6 12 12 6
0,165
t
RCc final final initial
initial
c
t
k n
ch e
V V V V e
V V
switch at V Volt
e
t ms
Calculate
2nd charge track! Why?
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Discharge
Bollen
R = 15 k
C = 10 nF
Vfinal = -12 V
Vinitial = +6 V
Switch at Vc = -6 Volt
15 .10
arg
6
6
6 12 12 6
0,165
t
RCc final final initial
initial
c
t
k n
disch e
V V V V e
V V
switch at V Volt
e
t us
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Frequency = 1 / (total time)
Bollen
arg
arg
0,165
0,165
0,33
3,03
ch e
disch e
total
oscillator
t ms
t ms
t ms
f kHz
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Variations 1
Bollen
By using diodes;
Charge time
and
Discharge time
are different !!
Treshold remains the same
So … duty cylce is controlable; up time ≠ down time
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Variations 2
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Frequency
control by
changing
the voltage
divider
Vtreshold up
Vtreshold low
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Summary 1
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Analyse
yourself
..
..
..
Conclusion?
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Summary 2
Bollen
Analyse
yourself
..
..
..
Conclusion?