Zener diode:
Zener diode,also sometime called the breakdown diode,is a P-N junction diode specially designed for operation in the breakdown region in reverse bias condition. the diode may use either zener breakdown mechanism or avalanche breakdown mechanism.
the breakdown diode may be silicon or germanium one but silicon is preferred over germanium because of higher operating tempature and current capability.
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| symbol of a zener diode |
Zener diode are connected into circuits with their cathodes as the positive terminal because they operate in the reverse-bias mode.small zener diodes are marked the same way as conventional diodes with a cathode band.The larger diodes are marked with the zener diode.
The symbol of zener diode is given figure this is similar to that of a normal diode except that the line representing the cathode is bent at both ends i.e the bar is turned into Z-shape; stand for zener.
construction of a zener diode:
Zener diode is like an ordinary P-N junction diode except that it properly doped so as to have a sharp breakdown voltage. There are several methods used in the manufacture of zener diodes, such as diffused structure ,diffused and passivated structure and alloy diffused structure.
Diffused structure zener diode consists of two N and P substrates diffused together and has metallic layers deposited on both sides to connect anode and cathode terminals as shown in figure. the drawback of such a construction is that the edge of the junction are exposed to contamination.
In passivated structure of a zener diode,the edges of the junction are covered by layer of sio2, as shown in fig 3.
similarly,all junctions are protected in alloy diffused structures as shown in figure 4.
In general, the alloy diffused structure gives better zener characteristics at lower zener voltages.on the other hand, diffused and passivated zener diode is used at higher zener voltages
construction of a zener diode:
Zener diode is like an ordinary P-N junction diode except that it properly doped so as to have a sharp breakdown voltage. There are several methods used in the manufacture of zener diodes, such as diffused structure ,diffused and passivated structure and alloy diffused structure.
Diffused structure zener diode consists of two N and P substrates diffused together and has metallic layers deposited on both sides to connect anode and cathode terminals as shown in figure. the drawback of such a construction is that the edge of the junction are exposed to contamination.
In passivated structure of a zener diode,the edges of the junction are covered by layer of sio2, as shown in fig 3.
similarly,all junctions are protected in alloy diffused structures as shown in figure 4.
In general, the alloy diffused structure gives better zener characteristics at lower zener voltages.on the other hand, diffused and passivated zener diode is used at higher zener voltages
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