There are two differences:
a) the amount of feedback you allow
b) whether you wire a frequency-determining device into the circuit
First things first: ANY amplifier circuit that uses feedback, which these days is most of 'em because feedback improves the quality of an amp's output, will oscillate if there's enough feedback. This poses a real problem because the more feedback you use, the better the amp sounds. Your challenge, therefore, is to make an amp that uses not quite enough feedback to oscillate.
The other is equally critical. If you want oscillation you usually want it on a specific frequency. You can build an LC tank or a crystal into the circuit to determine the output frequency if you're building an oscillator; if you're building an amp you wouldn't do this.
Rc phase shift uses negative feedback.. Weinbridge uses both +ve and -ve feedback
difference between local oscillator and controlled oscillator
klystron can act as both an amplifier and oscillator whereas a reflex klystron can act as only an oscillator. klystron needs a buncher cavity(sometimes multiple bunchers) and a catcher cavity whereas a reflex klystron needs only one cavity. klystron bunches electrons in forward direction, whereas the other bunches in the reverse direction using a reflector plate. klystron needs i/p signal (accelerating or deccelerating potential) whereas the other dont.
The DC voltage for the amplifier (transistor or FET) runs for a series-fed oscillator through the inductance of the LC circuit. A shunt-fed oscillator uses a radio-frequency choke or a resistor to deliver DC voltage to the amplifier. For an oscillator the difference between serial-fed and shunt-fed is small. The choke resonance frequency can interact with the LC circuit resonance frequency. This problem happens only with shunt-fed. Furthermore series-fed needs less components. Therefore it is prefered for (low power) oscillators. The output circuit of an amp can be series-fed or shunt-fed, too. The additional DC current through the coil will drive a iron or ferrite core earlier into saturation. This is an disadvantage of serial-fed. At a high-voltage tube RF amp with say 2000V DC voltage, in the shunt-fed amp only the choke and the DC blocking capacity have to withstand the high voltage. This is an advantage of the shunt-fed solution.
An oscillator works in different ways in different electronic equipment. For example, there is a quartz oscillator in a quartz watch that can keep track of the time. A pendulum of a clock is an oscillator that goes back and forth using potential and kinetic energy.
The amplifier projects the audio signal into something we can comprehend. The oscillator creates a fixed or variable pitch, which is fed to the amplifier. Amplifiers are circuits which transfer an input signal into an output signal. Oscillators are autonomous circuits powered by a constant energy source. They produce a steady state signal e.g. a sinusoidal signal or a chaotic signal.
Rc phase shift uses negative feedback.. Weinbridge uses both +ve and -ve feedback
Oscillator is an electronic circuit which can generate oscillating sin signal without any oscillating input with use of positive feedback Multivibrator is a two stage RC coupled amplifier circuit which can generate squae signal without ac input
Negative feedback helps maintain stability in a system by counteracting any deviation from a set point, while positive feedback amplifies or enhances the deviation from the set point. Negative feedback loops help regulate processes in the body, such as temperature control, while positive feedback loops are less common and tend to lead to a change in the system.
All negative feedback systems, whether they be electronic, biological, or anything else, work by applying a negative feedback to the source signal, which is proportional in some way to the source signal. If the factor by which the amplifier corrects is high enough, oscillation will result (perhaps even runaway oscillation) How you make it happen depends upon the amplifier you use however -- though most work similarly enough. You could use a delay between output and feedback, or you could rely on a large amplifier gain.
oscillator frequency is different.crystal working piezo electric effect
difference between feedback and control
The main Difference between Voltage and Current Feedback Amplifiers is in the sampled(Output) signals. In Voltage feedback the sampled signal is voltage (Vf=Beta*Vo) where Vo is the sampled signal and for current feedback it is current signal (Vf=Beta*Io).
difference between local oscillator and controlled oscillator
The difference between an RC and LC is that the frequency - determining device in the RC oscillator is not a tank circuit. LC can operate with A or C biasing, while RC can only operate with A.
An ordinary amplifier can have high gain but is unstable, drifts, can oscillate, etc. An amplifier with negative feedback has lower gain but is stable, does not drift, won't oscillate, etc.
Differential Amplifier or Summing Amplifier are usually used in a closed loop control system. The error signal will be the DIFFERENCE between the setpoint value and feedback value for Differential Amplifier. Whereas for Summing Amplifier, the error signal will be the difference between the setpoint value and feedback value only if one of the value is inverted in polarity. Another reason Op Amp is used: amplify the error signal as error signals are usually very small. Hope this helps.