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CHAPTER 2
OSCILLATORS
LEARNING OBJECTIVES
Upon completion of this chapter you will be able to:
1. List the two broad classifications of oscillators (wave generators).
2. Identify the three frequency-determining devices for sine-wave oscillators.
3. Describe the differences between series-fed and shunt-fed oscillators.
4. Explain how the crystal is equivalent to the series and parallel LC circuit.
5. Identify the Armstrong oscillator.
6. Identify the Hartley oscillator.
7. Identify the Colpitts oscillator.
8. Identify the resistive-capacitive oscillator.
9. Determine the frequency of a resistive-capacitive oscillator.
10. Explain the operation of a pulsed oscillator.
11. Determine how many cycles are present in the output of a pulsed oscillator.
12. Explain how frequency multiplication takes place.
INTRODUCTION
WAVE GENERATORS play a prominent role in the field of electronics. They generate signals from
a few hertz to several gigahertz (109 hertz). Modern wave generators use many different circuits and
generate such outputs as SINUSOIDAL, SQUARE, RECTANGULAR, SAWTOOTH, and
TRAPEZOIDAL waveshapes. These waveshapes serve many useful purposes in the electronic circuits
you will be studying. For example, they are used extensively throughout the television receiver to
reproduce both picture and sound.
One type of wave generator is known as an OSCILLATOR. An oscillator can be regarded as an
amplifier which provides its own input signal. Oscillators are classified according to the waveshapes they
produce and the requirements needed for them to produce oscillations.
CLASSIFICATION OF OSCILLATORS (GENERATORS)
Wave generators can be classified into two broad categories according to their output waveshapes,
SINUSOIDAL and NONSINUSOIDAL.
