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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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FAQs on PPT: Oscillator - Analog and Digital Electronics - Electrical Engineering (EE)

1. What is an oscillator?
An oscillator is an electronic circuit or device that generates a periodic, repetitive waveform, usually in the form of an electrical signal. It produces a continuous output signal with a specific frequency and amplitude.
2. How does an oscillator work?
An oscillator works by using positive feedback to sustain oscillations. It typically consists of an amplifier or an active element (such as a transistor or an operational amplifier), along with a feedback network. The feedback network ensures that a portion of the output signal is fed back to the input with the appropriate phase and amplitude, causing the circuit to continuously oscillate.
3. What are the applications of oscillators?
Oscillators have numerous applications in various fields. Some common applications include generating clock signals in digital systems, generating radio frequency signals in wireless communication systems, providing stable reference frequencies for precision instruments, and generating signals for audio synthesis in music production.
4. What are the different types of oscillators?
There are several types of oscillators, including: - LC Oscillators: These use inductors and capacitors to determine the frequency of oscillation. - RC Oscillators: These use resistors and capacitors to control the oscillation frequency. - Crystal Oscillators: These use a quartz crystal resonator to provide highly stable and accurate frequencies. - Voltage-Controlled Oscillators (VCOs): These allow the frequency to be adjusted by varying a control voltage. - Phase-Locked Loop (PLL) Oscillators: These use a feedback loop to synchronize the oscillator frequency with an external reference signal.
5. How can I troubleshoot oscillator problems?
If you are encountering issues with an oscillator, here are a few troubleshooting steps you can follow: 1. Check the power supply: Ensure that the oscillator is receiving the correct voltage and that the power supply is stable. 2. Inspect the connections: Verify that all the connections and components in the oscillator circuit are properly connected and intact. 3. Test the components: Use a multimeter or an oscilloscope to measure the resistors, capacitors, and other components for proper values. 4. Replace the oscillator component: If everything else seems fine, it might be necessary to replace the oscillator component itself. 5. Seek professional help: If the problem persists, it is advisable to consult an experienced technician or engineer for further assistance.
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