An oscillator is an amplifier that uses positive feedback to generate an output waveform without any external input signal. Positive feedback occurs when part of the output is fed back to the input in phase with the original signal. For oscillations to occur, the total phase shift around the feedback loop must be 180 degrees and the product of the open loop gain and feedback must equal unity, as stated by Barkhausen's criterion. The document discusses the basic theory, concept of positive feedback, and conditions for oscillations in an oscillator circuit.

1. Contents
• Definition
• Basic theory of oscillation
• Concept of positive feedback
• Barkhausen Criterion
• Condition for oscillation
• Conclusion and References
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OSCILLATORS

2. 2
Definition:
• An oscillator is an amplifier, which uses a positive feedback and
without any external input signal, generates an output waveform at a
desired frequency.
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3. 3
Basic Theory of Oscillators:
•The feedback is a property which allows to feedback
the part of the output, to the same circuit as its input.
•Such a feedback is said to be positive whenever the part
of the output that is feedback to the amplifier as its input,
is in phase with the original input signal applied to the
amplifier.
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4. 4
Concept of Positive Feedback
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5. 5
Barkhausen Criterian:
Block Diagram of Oscillator Circuit
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6. Conditions for Oscillations:
Barkhausen Criterion states that,
•The total phase shift around 180 deg.
•Product of open loop gain and its feedback is
unity
Aβ=1
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7. • Conclusion
From this presentation conclude that condition for
oscillator and some basic criterion.
• References
Thomas L.Floyd, “Electronic devices” Conventional
current version, Pearson prentice hall.
David A. Bell, “Electronic devices and circuits”, Oxford
University higher education.
Donald A Neamen, “Electronic Circuit Analysis and
Design” Tata McGraw Hill.
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