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
2 Oscillator: Output without INPUT
NO INPUT SIGNAL NOISE XOUTPUT
Amplifier: A(jw)
Feedback: b(jw) Do not forget about POWER Supply !!! XFEEDBACK
3 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”
4 Phase Shift Oscillator
5 Phase Shift Oscillator
6 Phase Shift Oscillator
7 Phase Shift Oscillator
8 Phase Shift Oscillator
9 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.
10 Three-point oscillator == Z1Z2Z3 Oscillator
11 Z1Z2Z3 Oscillator
12 Z1Z2Z3 Oscillator
13 Z1Z2Z3 Oscillator
14 Z1Z2Z3 Oscillator
15 Z1Z2Z3 Colpitts Oscillator. Example & Design
Advantage: One transistor only is needed. RF up to 1 GHz can be achieved
16 Z1Z2Z3. Hartley Oscillator
Simplified Common Drain Hartley Oscillator
17 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
18 Usage of Oscillator: (Simple) RF Transmitter Warning: Building RF transmitter without special permit is ILLEGAL
19 Crystal Oscillator Problem to be solved: Frequency Stability
But: Crystals for f > 50 MHz are too THIN and mechanically fragile
20 Varicap == Varactor == Voltage Controlled Capacitor
Usage: Voltage Controlled RLC
21 Varicap == Varactor == Voltage Controlled Capacitor
Usage: Voltage Controlled LC
22 Varicap usage: VCO == Voltage Controlled Oscillator https://www.edgefx.in/varactor-diode-circuit-working-and-characteristics/
23 Varicap : Electronic Tuning versus Mechanical Tuning
24 Control Questions
• What have I learned ?
25 Literature to read
1. TBD
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