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Oscillator Circuits
49 questions By Tony R. Kuphaldt
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Question 34 of 49
How many degrees of phase shift must the feedback circuit (the square box in this schematic) introduce to the signal in order for this inverting amplifier circuit to oscillate?
Reveal answerThe feedback network in this circuit must provide 180 degrees of phase shift, in order to sustain oscillations.
Notes:Ask your students to explain why the feedback network must provide 180 degrees of phase shift to the signal. Ask them to explain how this requirement relates to the need for regenerative feedback in an oscillator circuit.
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Question 35 of 49
How many degrees of phase shift must the feedback circuit (the square box in this schematic) introduce to the signal in order for this noninverting amplifier circuit to oscillate?
Reveal answerThe feedback network in this circuit must provide 360 degrees of phase shift, in order to sustain oscillations.
Notes:Ask your students to explain why the feedback network must provide 180 degrees of phase shift to the signal. Ask them to explain how this requirement relates to the need for regenerative feedback in an oscillator circuit.
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Question 36 of 49
Identify the type of oscillator circuit shown in this schematic diagram, and explain the purpose of the tank circuit (L1 and C1):
Also, write the equation describing the operating frequency of this type of oscillator circuit.
Reveal answerThis is a Meissner oscillator circuit, and the tank circuit establishes its frequency of operation.
$$f = \frac{1}{2{\pi}\sqrt{L_1 C_1}}$$
Notes:Ask your students to describe the amount of phase shift the tank circuit provides to the feedback signal. Also, ask them to explain how the oscillator circuit’s natural frequency may be altered.
This circuit is unusual, as inductors L2 and L3 are not coupled to each other, but each is coupled to tank circuit inductor L1.
