Diode Limiter

The diode limiter also called Clipper as it is used to limit the input voltage.when the positive cycle of the input wave comes, the diode becomes forward biased (fig. 2). As the cathode now at zero volts 0 v,the anode cannot exceed 0.07 volts assuming diode is a silicon diode.

So it limited to 0.7 volts as positive cycles comes from input voltage.When negative cycle comes the diode become reverse biased and at the output load we only get the negative cycle with clipped positive cycle.

And if we put the diode in reverse we will get the positive cycle with the clipped negative cycle
as shown below in the figure.





Figure 1: Shows the input
Figure 2: positive cycle clipped.
Figure 3: Negative cycle clipped.
Figure 4: Both the positive and negatice cycles are clipped. Read More!

P Type Semiconductors

When the trivalent impurity atoms like aluminium (Al), boron (B), indium (In) and gallium (Ga) having three valence electrons are added to silicon,after forming covalent bond one hole remains in silicon which need fourth electrons.As much as impurities atoms added more holes are produced called majority carriers.
The number of holes can be controled by impurites atoms added to silicon.The majority of current carriers is P-type material.There are also some free electrons produced when electron holes are thermally treated.These electrons are the minority carriers in p-type material. Read More!

N Type Semiconductors

Doping:

The conductivity of silicon and germenium can be drastically increased by the controlled addition of impurities to the intrinsic (pure) semiconductor material. This process, called doping, increases the number of current carriers (electrons or holes).

N Type Semiconductor:

To increase the number of conduction band electrons , pentavalent impurity atoms like arsenic (As), phosphorus (P), bismith(Bi) and antimony (Sb) are added.
Each pentavalent atom leaves an extra free conduction electron after combining with the silicon atom forming covalent bond.As pentavalent atom gives an electron so called donar atom.
The number of conduction electrons can be controled by the impurities ato added to silicon.

Most of current carriers are electron,silicon doped with pentavalent atoms is an n-type semiconductor material.The electrons are called majority carriers.There are also some holes when electrons are paired when thermally processed.These holes are called minority carriers. Read More!