16 March 2010

AF AND RF CHOKES(COIL)

There are two types of chokes mostly used ratio.

   1. Audio-Frequency chokes
   2. Radio-Frequency chokes



AUDIO-FREQUENCY CHOKES:
                                                                                       The Importance offered by an inductance is directly proportional to the frequency,and in the audio range of 20 Hz to 10 KHz,the value of inductance required is relatively high.So,in order to increase the inductance at audio frequencies,the coils are wound on a core of ferromagnetic material.The losses due to eddy currents are minimized by making the core from number of very thin sheets which are insulated from each other.These are called lamination or stampings and may be in number of standard shapes and sizes.




                                                                  AF Choke

RADIO-FREQUENCY CHOKES: 
                                                           These are designed to operate at high frequencies above audio range and are referred to either as intermediate frequency chokes or radio frequency chokes.In this type of inductor it is desirable that the coil should have as high an inductance as possible to a wide band of frequencies.The losses are not so important as in tuning coils, but in order to keep the self capacitance low,two types of winding are used,one of which is the single layer solenoid,but made very thin to keep the capacitance small.to single layer winding is used for high radio frequencies other winding is multilayer which is used for low radio frequencies.

 
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