oscillators-2p - Oscillator Circuits II Oscillator...

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1 Oscillator Circuits II. Oscillator Operation For self-sustaining oscillations: • the feedback signal must positive • the overall gain must be equal to one (unity gain)
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2 If the feedback signal is not positive or the gain is less than one, then the oscillations will dampen out. If the overall gain is greater than one, then the oscillator will eventually saturate. Types of Oscillator Circuits A. Phase-Shift Oscillator B. Wien Bridge Oscillator C. Tuned Oscillator Circuits D. Crystal Oscillators E. Unijunction Oscillator
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3 A. Phase-Shift Oscillator Frequency of the oscillator: (the frequency where the phase shift is 180º) Feedback gain β = 1/[1 5 α 2 – j ( 6 α α 3 ) ] where α = 1 / ( 2 π fRC) Feedback gain at the frequency of the oscillator β = 1 / 29 The amplifier must supply enough gain to compensate for losses. The overall gain must be unity. Thus the gain of the amplifier stage must be greater than 1/ β , i.e. A > 29 The RC networks provide the necessary phase shift for a positive feedback. They also determine the frequency of oscillation.
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  • Fall '11
  • UmutSezen
  • Electronic oscillator, Colpitts Oscillator, Wien Bridge Oscillator, HARTLEY OSCILLATOR, B. Wien Bridge Oscillator