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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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slide1

Signal Generators

Oscillators

November 2, 2007

slide2
HW:

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

November 2, 2007

signal generators oscillators
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

wien bridge oscillator
Wien-bridge oscillator

without amplitude stabilization.

November 2, 2007

wien bridge w amp stabil
Wien bridge w/ Amp. Stabil.

limiter used for amplitude control.

November 2, 2007

phase shift oscillator
Phase Shift Oscillator

November 2, 2007

quad osc circuit
Quad Osc. Circuit

November 2, 2007

active tuned osc
Active Tuned Osc.

November 2, 2007

equiv ckt
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

collpits oscillator
Collpits Oscillator

November 2, 2007

piezzoelectric crystal
Piezzoelectric Crystal

November 2, 2007

pierce oscillator
Pierce Oscillator

CMOS inverter as an amplifier.

November 2, 2007

bistable operation
Bistable Operation

November 2, 2007

bistable
Bistable

November 2, 2007

hysteresis
Hysteresis

November 2, 2007

noisy signal
Noisy Signal

November 2, 2007

limiter
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

astable w feedback
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

astable
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

ckt for triang square wave
Ckt for triang/square wave

A general scheme for generating triangular and square waveforms.

November 2, 2007

555 ic
555 IC

internal circuit of the 555 integrated-circuit timer.

November 2, 2007

555 for monostable
555 for monostable

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

November 2, 2007

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

November 2, 2007

triangle sinusoid
Triangle  Sinusoid

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

November 2, 2007

slide33

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

November 2, 2007

slide34

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

November 2, 2007

superdiode
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

slide36

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