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Explain the elementaryidea of an oscillatorwith the help of blockdiagram . |
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Answer» SOLUTION :Oscillator : An oscillatoris an electronicdevice which generatesan AC signal from a DC source.Oscillatorsare used in radio /TVreceiverset, radio/TV transmitters,RADAR, smartphones and microwavesovens. No inout is applied to the oscillator,yet an output is obtained from it. An oscillator requiresan AMPLIFIER and a feeback networkwith frequencydetermining components. when a part of the outputof an amplifier is coupled to the input of theamplifier, it is calledfeedback. When the feedbacksampleis out ofphase with theinput, it is callednegative feedback.When the feedback sampleis in phasewith theinput, it is calledpositive feedback. For an oscillator, a positivefeedback is required. The block diagram of oscillatoris shownbelow :  The VOLTAGE gain of a complete system is givenby `A_(f)= (A)/(1- A beta)` Where `A_(f)` is the voltagegain withfeedback, A isvoltagegain withoutfeedback and `beta` is the feedback factor. If for some FREQUENCY `Abeta = 1`, then the systemgain becomes `oo` and the circuit beginsto oscillate at that frequency. This condition`(Abeta = 1)` is called the Barkhausen criterionfor sustainedoscillations. The frequencyof oscillations depends on the LC or RC combinations used in a feedbacknetwork. When the power supply connectedto the oscillator is turned ON,electrical noise of a widerange of a frequenciesisgeneratedin the circuit, butthe condition`Abeta =1` is satisfiedonly for a particularfrequencyand the oscillatorat that frequency . |
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