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 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 . Example & Design

Advantage: One only is needed.  RF up to 1 GHz can be achieved

16 Z1Z2Z3.

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 Problem to be solved: Frequency Stability

But: Crystals for f > 50 MHz are too THIN and mechanically fragile

20 Varicap == Varactor == Voltage Controlled

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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