How do diodes work?

Question

I know what they do, only allow electricity to flow one way through them, but what goes on inside a diode, in laymans terms please.

Answer 1

Imagine a 3-dimensional array (crystal structure) of Silicon atoms. By themselves they are considered an inuslator -- not a good conductor of electrons. This is because all of the electrons in the outer shell of the Silicon are well bonded to each of its neighbors in all 3 dimensions. They just don't want to move when an external electric field (battery) is applied.

But if you add a few Phosphorus atoms in place of the Silicon atoms (like one Phosphorus for every billion Silicon atoms), then you have a few extra electrons just hanging around that are free to move, because Phosphorus has 6 valence electrons instead of 5 like Silicon (other possible 6-valence atoms would be Arsenic and Antimony). This 'doped' (with Phosphorus) Silicon crystal is now an N-type silicon crystal.

Now, take some more pure Silicon crystal and dope it with Aluminum or Boron, (with only 4 valence electrons) and you have P-type silicon. In P-type silicon current can still 'flow' by action of 'holes' or places by the Boron atoms where there is a lack of an electron.

OK... now place the P-type crystal next to the N-type crystal. Without even hooking up a battery to this diode, the extra electrons from the N side are going to physically move across to the P side where the holes are and fill them up, so you end up with a region that looks just like pure silicon (the non-conductor) -- 5 valence electrons around each atom in the 3-D crystal lattice.

Now, if you apply a voltage in the forward direction, current will begin to flow, because all those mobile electrons and holes from the dope atoms are still mobile. After the forward voltage reaches approximately 1/2 volt, a lot of current will start to flow.

If you reverse the battery, the electrons and holes will be sucked away from the middle (like charges oppose, opposite charges attract) and it will take a great amount of energy to overcome the created gap in the middle of the junction (the reverse breakdown or zener voltage). In other words, no current flows (until you reach the zener point).

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Answer 2

lots of info with pictures and diagrams at this site

In electronics, a diode is a component that restricts the directional flow of charge carriers. Essentially, a diode allows an electric current to flow in one direction, but blocks it in the opposite direction. Thus, the diode can be thought of as an electronic version of a check valve. Circuits that require current flow in only one direction typically include one or more diodes in the circuit design.

Early diodes included "cat's whisker" crystals and vacuum tube devices (called thermionic valves in British English). Today the most common diodes are made from semiconductor materials such as silicon or germanium.

Answer 3

You have to know about p-n juction semi-conductors. They have electrical properties that allow flow in one direction but not the other.
Most modern diodes are based on semiconductor p-n junctions. In a p-n diode, conventional current can flow from the p-type side (the anode) to the n-type side (the cathode), but cannot flow in the opposite direction.

Answer 4

Actually,

diodes is one way current so its check current path
so if path is correct , its act like key

path is correct key is on current can go through also key is off

and u can use it in many things like in notifications