Instead, a diode will have negligible resistance in one direction (to allow current flow), and very high resistance in the reverse direction (to prevent current flow). A point contact diode (with glass encapsulation) and a Schottky diode. In this the semiconductor crystal acts as cathode and metal wire acts as anode. This diode is built of n – type semiconductor and few conducting metals placed to be in contact with the semiconductor. A diode is constructed by fabricating p and n regions in Si as shown schematically on Figure 3(a). pressure contact used in the point-contact diode compared with the deposited contact in the Schottky diode. This is also known as Cat’s whisker which is a type of point contact diode. Although in the real world, diodes can not achieve zero or infinite resistance. At the point of contact of the P-Type and N-Type regions, the holes in the P-Type attract electrons in the N-Type material. The pressure contact in the point-contact diode can damage the junction, depending on the amount of pressure exerted on the contact, while the Schottky diode lends itself to better control and more repeatable fabrication. Hence the electron diffuses and occupies the holes in the P-Type material. 3. Zener Diodes with glass or black resin encapsulation. It is just a device under this condition. These are some of the most common types of diodes used in designing and operation of electronic circuits. p region n region + Vd - Id (a) Id To summarize, there is no flow of current in an unbiased pj junction diode. In other words, this operating point (Q point) is the intersection where the optimum forward voltage and forward current converge, and it is also the point where the diode operates at its optimum. 5. Point contact diodes are used for low voltage signal & in microwave mixer & detectors. 16. Point contact diodes – The construction of this diode is simpler and are used in analog applications and as a detector in radio receivers. A selection of light emitting diodes. Mode of operation Its operation depends on the pressure of contact between semiconductor crystal and point. At this point, the conduction band and valence band no longer overlap and the tunnel diode operates in the same manner as a normal p-n junction diode. The barrier potential is exactly balanced by the contact potential at the metal-semiconductor contacts at the ends of diode terminals. 4. The Importance of a Q point to Circuit Operation. A diode is effectively like a valve for an electrical circuit.. Semiconductor diodes are the most common type of diode. Another way of expressing a Q point is by addressing it as biasing. This is the reason, the voltmeter is unable to measure the barrier potential of diode. In this a metal wire is present which is pressed against the semiconductor crystal. Crystal Diode. 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