Oscillator Circuits
The three major oscillator circuits often used in Amateur Radio equipment are the Colpitts, Hartley and Pierce oscillators. In order for a circuit to oscillate, it must have a positive feedback loop with a gain greater than 1. The Colpitts, Hartley, and Pierce oscillator circuits are shown in the figure below. In each circuit, its feedback supply has been circled. In the Colpitts oscillator, feedback is taken from the capacitive divider. In the Hartley oscillator, it is taken from a tapped coil, and in the Pierce oscillator, a crystal feedback element is used.
Exam Questions
What are three major oscillator circuits often used in Amateur Radio equipment?
A. Taft, Pierce and negative feedback
B. Pierce, Fenner and Beane
C. Taft, Hartley and Pierce
D. Colpitts, Hartley and Pierce
What condition must exist for a circuit to oscillate?
A. It must have at least two stages
B. It must be neutralized
C. It must have a positive feedback loop with a gain greater than 1
D. It must have negative feedback sufficient to cancel the input signal
How is positive feedback supplied in a Hartley oscillator?
A. Through a tapped coil
B. Through a capacitive divider
C. Through link coupling
D. Through a neutralizing capacitor
How is positive feedback supplied in a Colpitts oscillator?
A. Through a tapped coil
B. Through link coupling
C. Through a capacitive divider
D. Through a neutralizing capacitor
How is positive feedback supplied in a Pierce oscillator?
A. Through a tapped coil
B. Through link coupling
C. Through a neutralizing capacitor
D. Through a quartz crystal