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# Lecture Notes - Chapter 9

## Oscillators

(These Lecture Notes are for courses using the book the Complete Electronics Self-Teaching Guide with Projects. Instructors of courses using that text are permitted to use these Lecture Notes as-is or adapt them for their use).

• Understanding Oscillators
• Discuss the three sections of an oscillator.
• Introduce the term: negative feedback (figure 9.3).
• Introduce the term: positive feedback (figure 9.4).
• Positive feedback can cause an amplifier to oscillate even when there is no external input.
• Introduce the term: resonant load (figure 9.8).
• Feedback
• Discuss the feedback method used in a Colpitts oscillator (figure 9.11 (1)).
• Discuss the feedback method used in a Hartley oscillator (figure 9.11 (2)).
• Discuss the feedback method used in an Armstrong oscillator (figure 9.11 (3)).
• The Colpitts Oscillator
• Discuss the Colpitts oscillator circuit (figure 9.15).
• Feedback is taken from a connection between the two capacitors in the resonant circuit.
• Review the equation used to calculate the resonance frequency of a Colpitts oscillator.
• Review the equation used to determine the fraction of the output voltage used as feedback in the Colpitts oscillator.
• Project 9.1: The Colpitts Oscillator
• Discuss the objective of the project.
• Review the circuit diagrams (figure 9.18 and 9.19).
• Review the test setup (figure 8.21).
• Discuss how to calculate the frequency from the measured period.
• The Hartley Oscillator
• Discuss the Hartley oscillator circuit (figure 9.27).
• Feedback is taken from a tap partway down the coil, or if two inductors are used, a connection between the two inductors in the resonant circuit.
• Project 9.2: The Hartley Oscillator
• Discuss the objective of the project.
• Review the circuit diagram (figure 9.30).
• Review the test setup (figure 9.32)
• The Armstrong Oscillator
• Discuss the Armstrong oscillator circuit (9.35).
• Simple Colpitts Oscillator Design Procedure
• Review the equation to determine the value of C1.
• Discuss the calculation to determine the value of C2.
• Discuss the calculation to determine the value of RC.
• Discuss the calculation to determine the value of CC and CB.

This page includes material extracted, by permission of the publisher, Wiley Publishing, from Complete Electronics Self-Teaching Guide with Projects, ISBN: 9781118217320.