Energy Band Theory of Crystals: Energy Band Theory of Crystals – As discussed above, it is revealed that most metals and semiconductors are crystalline in structure and a crystal is made up of a space array of atoms or molecules (strictly speaking, ions) in regular repetition in three dimensions of some fundamental structural unit. For […]
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What is Crystalline Structure? What is Crystalline Structure? – Solids are characterized by incompressibility, rigidity and mechanical strength. This indicates that the molecules, atoms or ions that make up a solid are closely packed, i.e., they are held together by strong forces and cannot move at random. On the contrary, gases are characterized by a
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Compound Semiconductor Materials: Most of the compound semiconductor materials are formed from the combinations of group III and group V elements. A portion of the periodic table listing the more common semiconductors is given in Table 6.2. A list of some semiconductor materials is given in Table 6.3. Two element compounds are called the binary
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Elemental Semiconductor Materials: Group IV includes five elements viz., Carbon (C), Silicon (Si), Germanium (Ge), Tin (Sn) and lead (Pb). The elements of this subgroup show marked similarity as well as gradation in properties with rise of atomic number and on these grounds, their inclusion in the same subgroup is perfectly justified. Following are the
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Thyratron Working Principle: Thyratron is a hot cathode gas filled triode. Normally it is filled with a small amount of inert gas such as argon, hydrogen, neon or mercury vapour. The fast acting devices do not use mercury vapour as the mercury vapour has the disadvantage of characteristics varying with temperature and it takes time
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Construction of Phanotron: The constriction of a gas-filled diode or phanotron is similar to a vacuum diode except that the size of its electrodes is larger so as to conduct heavy currents. As far as the symbolic representation of the gas-filled tubes is concerned, they are usually represented by a dot in the circle with
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Cold Cathode Gas Filled Diode: The cutaway view of a Cold Cathode Gas Filled Diode is shown in Fig. 5.24. It essentially consists of two electrodes, namely cathode and anode, mounted fairly close together in a glass envelope. The anode is in the form of a thin wire, while cathode is of cylindrical metallic surface
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Explain Conduction in Gas: Explain Conduction in Gas – The introduction of small amount of gas into the electron evacuated tubes entirely changes the operating characteristics—materially giving in general a greatly diminished voltage drop and correspondingly increased current. When the cathode of a vacuum tube is heated to its emitting temperature electrons are driven off
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Classification of Gas Filled Tubes: Vacuum tubes are no doubt, extensively used in communication control and industrial electronic circuits, but these can carry small plate currents (typically from 1 mA to 100 mA). For certain applications much large currents (from 1 A to 100 A) are required. Gas-filled electron tubes are generally used for such
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Construction and Working of Vacuum Pentode: In order to retain the advantages of screen grid and eliminate the harmful effects of attracting the electrons due to secondary emission by the screen grid, an additional third grid, known as suppressor grid, may be inserted between the screen grid and the plate. The tube having five electrodes, a
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