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Signal Generators. Oscillators. HW: Due Friday Nov. 9 13.4,13.14,13.23,13.27 . SIGNAL GENERATORS /OSCILLATORS. A positive-feedback loop is formed by an amplifier and a frequency-selective network. In an actual oscillator circuit, no input signal will be present.

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Signal Generators

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Signal Generators

Oscillators

November 2, 2007


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HW:

Due Friday Nov. 9 13.4,13.14,13.23,13.27

November 2, 2007


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SIGNAL GENERATORS /OSCILLATORS

A positive-feedback loop is formed by an amplifier and a frequency-selective network

In an actual oscillator circuit, no input signal will be present

November 2, 2007


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Oscillator-frequency stability

November 2, 2007


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Limiter Ckt Comparator

November 2, 2007


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Wien-bridge oscillator

without amplitude stabilization.

November 2, 2007


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Wien bridge w/ Amp. Stabil.

limiter used for amplitude control.

November 2, 2007


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Alternate Wien bridge stabil.

November 2, 2007


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Phase Shift Oscillator

November 2, 2007


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Phase Shift. Osc. W/ Stabil.

November 2, 2007


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Quad Osc. Circuit

November 2, 2007


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Active Tuned Osc.

November 2, 2007


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OPAMP based Tuned Amp. Osc.

November 2, 2007


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Colpitts and Hartley Oscillators

November 2, 2007


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Equiv. Ckt

To simplify the analysis, negtlect Cm and rp

Consider Cp to be part of C2, and include ro in R.

November 2, 2007


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Collpits Oscillator

November 2, 2007


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Piezzoelectric Crystal

November 2, 2007


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Pierce Oscillator

CMOS inverter as an amplifier.

November 2, 2007


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Bistable Operation

November 2, 2007


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Bistable

November 2, 2007


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November 2, 2007


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Hysteresis

November 2, 2007


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Noisy Signal

November 2, 2007


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Limiter

(b)L+ = VZ + VD1 + VD2 and L– = –(VZ + VD3 + VD4).

a) L+ = VZ1 + VD and L– = –(VZ2 + VD),

Limiter circuits = more precise output levels for bistable circuit.

R according to current required for the proper operation of the zener diodes.

November 2, 2007


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Astable w/ feedback

Abistable multivibrator with inverting transfer characteristics in a feedback loop with an RC circuit results in a square-wave generator.

November 2, 2007


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Astable

The circuit obtained when the bistable multivibrator is implemented with the circuit

(This circuit is called an astable multivibrator.)

c) Waveforms at various nodes of the circuit in (b).

November 2, 2007


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Ckt for triang/square wave

A general scheme for generating triangular and square waveforms.

November 2, 2007


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(a) An op-amp monostable circuit. (b) Signal waveforms in the circuit of (a).

November 2, 2007


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555 IC

internal circuit of the 555 integrated-circuit timer.

November 2, 2007


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555 for monostable

a) The 555 timer connected to implement a monostable multivibrator. (b) Waveforms of the circuit in (a).

November 2, 2007


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555 for astable

  • The 555 timer connected to implement an astable multivibrator. (b) Waveforms of the circuit in (a).

November 2, 2007


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Triangle  Sinusoid

Using a nonlinear (sinusoidal) transfer characteristic to shape a triangular waveform into a sinusoid.

November 2, 2007


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(a) A three-segment sine-wave shaper. (b) The input triangular waveform and the output approximately sinusoidal waveform.

November 2, 2007


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A differential pair with an emitter degeneration resistance used to implement a triangular-wave to sine-wave converter.

November 2, 2007


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Superdiode

when vI> 0 and the diode conducts, the op amp supplies the

load current, and the source is conveniently buffered,

an added advantage.

(a) The “superdiode” precision half-wave rectifier and (b) its almost ideal transfer characteristic.

November 2, 2007


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  • An improved version of the precision half-wave rectifier: Diode D2 is included to keep the feedback loop closed around the op amp during the off times of the rectifier diode D1, thus preventing the op amp from saturating.

  • The transfer characteristic for R2 = R1.

November 2, 2007


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