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Explain how transistor can be used as an oscillator ? |
Answer» Solution :(i) In an oscillator, we get ac output without any external input signal.  (ii) Here L-Ccircuit in emitter-base circuit of transistorwhich is forward biased with battery `V_(B B )` . The collector emitter circuit is reverse biased with battery `V_( C C ) `. (iii) A coil `L_(1)` is inserted in collector emitter circuit . It is coupled with L. Working `:` (i) If we close the key ( K ) , weak collector current start RISING with time due to the inductance `L_(2)`. As a result,INCREASING magnetic flux is linked with `L_(1)` and `l.` brgt (ii) Due to mutual induction, anemf is induced in L which will charge the upper plate ofcapacitor ( C ) , CONSEQUENTLY there will be support to the forward of emitter base circuit. (iii) This results in an increasing in the emitter current and hence an increase in the collector current. (iv) Due to it, more increasing magnetic flux is linkedwith `L_(10` & L . (v) The aboveprocess continues till the collector current becomes maximum ( or ) saturated. (vi) The resonant frequency of tuned circuit at which the oscillator will oscillate. `v =(1)/( 2pi sqrt( LC))` |
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