Analog Sinusoidal Oscillator Part 2

Electronic Instrumentation
Analog Sinusoidal Oscillators
Part 2
* In this presentation definitions and examples
from Wikipedia, HowStaffWorks and some other sources
were used
Lecturer: Dr. Samuel Kosolapov
Items to be
defined/refreshed/discussed
• Alternative Way to validate if specific circuit is
Oscillator
• Phase Shift Oscillator
• Bubba Oscillator
• Z1Z2Z3 Oscillators
• Crystal Oscillators
• VCO
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Oscillator: Output without INPUT
NO INPUT
SIGNAL
NOISE
XOUTPUT
Amplifier: A(jw)
Feedback: b(jw)
XFEEDBACK
Do not forget about
POWER Supply !!!
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Alternative Way to validate if specific circuit is Oscillator
==
We have now “standard” Analog Electronic problem:
IF
Vin’ == Vin () (but for only ONE frequency !!!)
THEN the circuit is oscillator
1. EE can be “smart”: Break loop when Zin is infinity.
2. Number of blocks can be > 2: It may be not clear which block
is amplifier, and which one is “feedback”
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Phase Shift Oscillator
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Phase Shift Oscillator
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Phase Shift Oscillator
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Phase Shift Oscillator
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Phase Shift Oscillator
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Bubba Oscillator
http://www.ti.com/lit/ml/sloa087/sloa087.pdf
The RC sections each contribute 45° phase shift,
The gain, A, must equal 4
for oscillation to occur.
The test circuit oscillated at 1.76 kHz
Rather than the ideal frequency of 1.72 kHz
when the gain was 4.17
rather than the ideal gain of 4.
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Three-point oscillator == Z1Z2Z3 Oscillator
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Z1Z2Z3 Oscillator
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Z1Z2Z3 Oscillator
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Z1Z2Z3 Oscillator
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Z1Z2Z3 Oscillator
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Z1Z2Z3 Colpitts Oscillator. Example & Design
Advantage: One transistor only is needed.
 RF up to 1 GHz can be achieved
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Z1Z2Z3. Hartley Oscillator
Simplified
Common Drain
Hartley Oscillator
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Clapp Oscillator
It was published by James Kilton Clapp in 1948
Oscillators of this kind were independently developed by several inventors,
and one developed by Gouriet had been in operation at the BBC since 1938.
Simplified Clapp
Oscillator
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Usage of Oscillator: (Simple) RF Transmitter
Warning: Building RF transmitter without special permit
is ILLEGAL
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Crystal Oscillator
Problem to be solved:
Frequency Stability
But: Crystals for f > 50 MHz
are too THIN and
mechanically fragile
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Varicap == Varactor == Voltage Controlled Capacitor
Usage: Voltage Controlled RLC
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Varicap == Varactor == Voltage Controlled Capacitor
Usage: Voltage Controlled LC
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Varicap usage: VCO == Voltage Controlled Oscillator
https://www.edgefx.in/varactor-diode-circuit-working-and-characteristics/
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Varicap : Electronic Tuning versus Mechanical Tuning
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Control Questions
• What have I learned ?
25
Literature to read
1. TBD
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