Construction Of Automatic Phase Changer

Doping [semi-conductor]
In semi-conductor production, doping is the process of intentionally introducing impurities into an extremely pure semi conductor to change its electrical properties. The impurities are dependent upon the type of semi conductor lightly and moderately doped semi conductors are referred to as extrinsic semi-conductor of its p-n junction.
P-n junction
A P-n junction is formed by joining p-type and n-type semi conductors together in very close contact. The term junction refers to the boundary interface where the two regions of the semi conductor meet.
Electron
The electron is a sub-atomic particle carrying a negative electric charge. It has no known components or substructure, and therefore is believed to be an elementary particle. An electron has a mass that is approximately 1/1836 that of the proton. The intrinsic angular momentum of the is as to tunnel from the valence band of the p-type material to the conduction band of the n-type material. In the atomic scale, this tunneling corresponds to the transport of valence band electrons into the empty conduction band states, as a result of the induced barrier between these bands and high electric fields that are induced due to the relatively high levels of dopings on  both sides.
The breakdown voltage can be controlled by quite accurately in the doping process. While tolerances within 0.05 % are available the most widely used tolerances are 5% and 10%.
Breakdown voltage for commonly available zener diode can vary widely from 1.2volts to 200volts. Another mechanism that produces a similar effect as in the avalanche.
Avalanche diode
An avalanche diode is a diode that is designed to go through avalanche breakdown at a specified reverse bias voltage and conduct as a type of voltage reference.
The two types of diode are in fast constructed the same way and both effects are present in diodes of this type. In silicon diodes up to about 5.6volts, the zaner effect is the predominant effect and shows a marked negative temperature. Above 5.6vo its the avalanche breakdown.
Avalanche breakdown
Avalanche breakdown is a phenomenon that can occur in both insulating and semi conducting materials. It is a form of break down which occurs in junction which have been lightly doped. Have wide depletion layers where the electric field is not strong enough to production zanier breakdown,
Modern manufacturing technicaves have produced devices with voltages lower than 5.6v with negligible temperature coefficient, but as higher voltage devices are encountered the temperature officious rises dramatically. A 75v diode has 10 times the coefficient of a 12v diode all such diodes regardless of breakdown voltage are usually marketed under the numbrella term of zener diode,