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How does varactor diode help produce fm?

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abishek

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doping profile of 1n4007

how does it help produce fm ??
 

neils_arm_strong

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Re: varactor diode

varactor diode has a capacitance which depends on the applied voltage.So if a random message signal is applied as the voltage to a varactor which is a part of a tank circuit,then the frequency of the tank circuit varies in accordance with the message.Thus an FM wave can be generated.
 

electronics_kumar

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Re: varactor diode

FM can be generated by means of direct method or indirect method( form PM) ...
in the case of Direct method, circuit reactance will varied..since circuit reactance will determine frequency of output signal.....if reactance is varied w.t .r mesaage signal than output signal freq. will be varied.it is nothing but FM signal..
for varactor diode,under reverse bias its capacitance varies inversely...
Vα (1/√C)**n...n a constant dependinfg upon doping profile
if reverse bias varied inaccordance with message ,ouptut is an FM signal
 

sivani_vs

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Re: varactor diode

Varactor diode is connected across a tuned circuit, and the modulating signal is applied across it. hence the central frequency of the tuned ckt varries in accordance with the modulating signal.
 

A.Anand Srinivasan

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Re: varactor diode

varactor diode is an electrically variable capacitor in reverse bias and hence is used in varying the frequency and hence helping in FM modulation
 

E-design

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Re: varactor diode

Note that most diodes have these varactor properties. For instance, a common 1N4007 rectifier diode will change its capacitance between 5-15pF when reversed biased between 1-15V. The thing that makes this different from a purposely manufactured varactor diode is the Q factor. The 1N4007 will only work in fairly low frequency circuits.
 

electronics_kumar

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varactor diode

okk...how diode is working as ordinary diode or as varactor ...it is just doping profile ..or any thing else
 

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