Diode

 

diode_g_1DIODE : Facts about a simple diode are »

(1) In Eletronics diode is a two terminal semiconductor component that conduct current in one direction ( primarily)

(2) It has very low resistance ( ideally zero) to flow the current in one direction(forward) ,and high resistance (ideally infinite) to flow the current in other direction(backward)

(3) A semiconductor diode is made by simply sandwitching N type and P type semiconductor , a simple diode has p-n junction

(4) The first semiconductor diode , called cat whisker diode that developed around 1906

(5) Today most diode made by silicon crystal (Si)

(6) Eletronic symbol of diode represented as shown in figure        download

(7) A diode has two terminal called as anode and cathode

(8) A diode can be used as :-

(A) Rectifiers  (B) Signal limiter (C) Switches (D) Voltage regulator (E)  Signal modulator (F) Signal mixer and many more

(9) A diode shows a very low resistance in one direction ( forward) and very high resistance in other direction ( backward) for current flow ,due to this property a diode can be used as switch

(10)  n type semiconductor formed by intrinsic semiconductor doped with a pentavalent impurity ( P,As ,Sb Bi)

(11)  p type semiconductor formed by intrinsic semiconductor doped with a trivalent impurity (Al,B Ga)

(12) Working Principle of Diode :-The n side will have large number of electrons and very few holes (due to thermal excitation) whereas the p side will have high concentration of holes and very few electrons. Due to this a process called diffusion takes place. In this process free electrons from the n side will diffuse (spread) into the p side and combine with holes present there, leaving a positive immobile (not moveable) ion in the n side. Hence few atoms on the p side are converted into negative ions. Similarly few atoms on the n-side will get converted to positive ions. Due to this large number of positive ions and negative ions will accumulate on the n-side and p-side respectively. This region so formed is called as depletion region. Due to the presence of these positive and negative ions a static electric field called as “barrier potential” is created across the p-n junction of the diode. It is called as “barrier potential” because it acts as a barrier and opposes the flow of positive and negative ions across the junction.

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