chapter 12 _Signal generators and waveform-shaping circuit

Oscillating frequency is the one that the phase shift

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Oscillating frequency is the one that the phase shift of the RC network is 180 0

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SJTU Yang Hua Microelectronic Circuits The Phase-Shift Oscillator A practical phase-shift oscillator with a limiter for amplitude stabilization.
SJTU Yang Hua Microelectronic Circuits The LC-Tuned oscillator Colpitts Oscillator A parallel LC resonator connected between collector and base. Feedback is achieved by way of a capacitive divider Oscillating frequency is determined by the resonance frequency. ) ( 1 2 1 2 1 0 C C C C L + = ϖ

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SJTU Yang Hua Microelectronic Circuits The LC-Tuned oscillator Hartley Oscillator A parallel LC resonator connected between collector and base. Feedback is achieved by way of an inductive divider. Oscillating frequency is determined by the resonance frequency. ) ( 1 2 1 2 1 0 C C C C L + = ϖ
SJTU Yang Hua Microelectronic Circuits Crystal Oscillators A piezoelectric crystal. (a) Circuit symbol. (b) Equivalent circuit.

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SJTU Yang Hua Microelectronic Circuits Crystal Oscillators Crystal reactance versus frequency (neglecting the small resistance r , ). A series resonance at A parallel resonance at s s LC 1 = ϖ ) ( 1 p s p s p C C C C L + = ϖ
SJTU Yang Hua Microelectronic Circuits Homework: June 12th, 2008 12.13;12.14

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SJTU Yang Hua Microelectronic Circuits Bistable Circuit -- three basic factors The output signal only has two states: positive saturation(L + ) and negative saturation(L - ). The circuit can remain in either state indefinitely and move to the other state only when appropriate triggered .(threshold voltage) The direction of one stage moving to the other stage. A positive feedback loop capable of bistable operation.
SJTU Yang Hua Microelectronic Circuits Bistable Circuit The bistable circuit (positive feedback loop) The negative input terminal of the op amp connected to an input signal v I . β o o v R R R v v = + = + 2 1 1

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SJTU Yang Hua Microelectronic Circuits Bistable Circuit The transfer characteristic of the circuit in (a) for increasing v I . Positive saturation L + and negative saturation L - β + = L V TH
SJTU Yang Hua Microelectronic Circuits Bistable Circuit The transfer characteristic for decreasing v I . β - = L V TL

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SJTU Yang Hua Microelectronic Circuits Bistable Circuit The complete transfer characteristics.
SJTU Yang Hua Microelectronic Circuits A Bistable Circuit with Noninverting Transfer Characteristics 2 1 1 2 1 2 R R R v R R R v v o I + + + = +

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SJTU Yang Hua Microelectronic Circuits A Bistable Circuit with Noninverting Transfer Characteristics The transfer characteristic is noninverting.
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• Fall '10
• ChengJianping
• Oscillators, Electronic oscillator, Multivibrator, Microelectronic Circuits, SJTU Yang Hua

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