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# PPT - Oscillator Electrical Engineering (EE) Notes | EduRev

## Electronic Devices

Created by: Cs Toppers

## Electrical Engineering (EE) : PPT - Oscillator Electrical Engineering (EE) Notes | EduRev

``` Page 1

CHAPTER 2:
OSCILLATOR
Page 2

CHAPTER 2:
OSCILLATOR
INTRODUCTION
?
convert dc energy to ac energy at a very high frequency.
?
If the feedback signal is large enough and has correct phase,
there will be an output signal even though there is no external
input signal.
?
The criterion is that the signal fed back to the input of the
amplifier must be in phase. In-phase feedback is also called
positive feedback, or regenerative feedback.
?
It is an unstable amplifier.
Page 3

CHAPTER 2:
OSCILLATOR
INTRODUCTION
?
convert dc energy to ac energy at a very high frequency.
?
If the feedback signal is large enough and has correct phase,
there will be an output signal even though there is no external
input signal.
?
The criterion is that the signal fed back to the input of the
amplifier must be in phase. In-phase feedback is also called
positive feedback, or regenerative feedback.
?
It is an unstable amplifier.
?
Electronic oscillators are divided into:
?
Sinusoidal (or harmonic) oscillators-which produce
an output having sine waveform
?
Non-sinusoidal (or relaxation) oscillator-the output is
square, rectangular or saw-tooth or pulse shape.
?
Oscillators are widely applied in many digital devices,
Signal generator, Touch-tone telephone, musical
instrument and radio/television transmitter and etc.
Page 4

CHAPTER 2:
OSCILLATOR
INTRODUCTION
?
convert dc energy to ac energy at a very high frequency.
?
If the feedback signal is large enough and has correct phase,
there will be an output signal even though there is no external
input signal.
?
The criterion is that the signal fed back to the input of the
amplifier must be in phase. In-phase feedback is also called
positive feedback, or regenerative feedback.
?
It is an unstable amplifier.
?
Electronic oscillators are divided into:
?
Sinusoidal (or harmonic) oscillators-which produce
an output having sine waveform
?
Non-sinusoidal (or relaxation) oscillator-the output is
square, rectangular or saw-tooth or pulse shape.
?
Oscillators are widely applied in many digital devices,
Signal generator, Touch-tone telephone, musical
instrument and radio/television transmitter and etc.
BLOCK DIAGRAM
Closed loop transfer function with positive feedback:
If,   ßA= 1 + j0 or   ßA = 1?0
o
Page 5

CHAPTER 2:
OSCILLATOR
INTRODUCTION
?
convert dc energy to ac energy at a very high frequency.
?
If the feedback signal is large enough and has correct phase,
there will be an output signal even though there is no external
input signal.
?
The criterion is that the signal fed back to the input of the
amplifier must be in phase. In-phase feedback is also called
positive feedback, or regenerative feedback.
?
It is an unstable amplifier.
?
Electronic oscillators are divided into:
?
Sinusoidal (or harmonic) oscillators-which produce
an output having sine waveform
?
Non-sinusoidal (or relaxation) oscillator-the output is
square, rectangular or saw-tooth or pulse shape.
?
Oscillators are widely applied in many digital devices,
Signal generator, Touch-tone telephone, musical
instrument and radio/television transmitter and etc.
BLOCK DIAGRAM
Closed loop transfer function with positive feedback:
If,   ßA= 1 + j0 or   ßA = 1?0
o
?
Barkhausen  criterion :
?
The feedback factor or loop gain . The gain is
infinite, this represent the condition for oscillation.
?
The net phase shift around the loop 0° (or an
integral multiple of 360° ). In other word, feedback
should be positive.
?
The amplifier gain must be greater than the loss in
the feedback path.
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