Vishay Techno electrical components, German Vishay Techno models, Vishay Techno prices

Vishay Techno electrical components are instruments that measure by converting high primary current to low secondary current based on the principle of electromagnetic induction. A current transformer consists of a closed iron core and windings. Its primary winding has very few turns and is connected in series with the circuit where the current needs to be measured. Therefore, the full line current often flows through it. The secondary winding has more turns and is connected in series with measuring instruments and protection circuits. When the current transformer is in operation, its secondary circuit is always closed, so the impedance of the measuring instrument and the protection circuit series coil is very small, and the operating state of the current transformer is close to a short circuit. The current transformer converts high primary current to low secondary current for measurement; the secondary side must not be open-circuited. The principle of the current transformer is based on electromagnetic induction. A current transformer consists of a closed iron core and windings. Its primary winding has very few turns and is connected in series with the circuit where the current needs to be measured, so the full line current often flows through it. The secondary winding has more turns and is connected in series with measuring instruments and protection circuits. When the current transformer is in operation, its secondary circuit is always closed, so the impedance of the measuring instrument and the protection circuit series coil is very small, and the operating state of the current transformer is close to a short circuit.

Vishay Techno electrical component parameters

(1) Nominal capacitance is the capacitance marked on the capacitor. However, there is a deviation between the actual capacitance of the capacitor and the nominal capacitance; the accuracy class corresponds to the allowable error. General capacitors commonly use classes I, II, and III, while electrolytic capacitors use classes IV, V, and VI to indicate capacitance accuracy, selected according to the application. The capacitance value of an electrolytic capacitor depends on the impedance presented during operation under AC voltage. The capacitance value changes with variations in operating frequency, temperature, voltage, and measurement method. The unit of capacitance is F (Farad). Since a capacitor is a "container" for storing electric charge, there is the issue of "capacity" size. To measure the ability of a capacitor to store electric charge, the physical quantity of capacitance is defined. A capacitor can only store electric charge under the action of an applied voltage. Different capacitors may store different amounts of charge under voltage action. Internationally, it is uniformly specified that when a DC voltage of 1 volts is applied to a capacitor, the amount of charge it can store is the capacitance of that capacitor (i.e., the charge per unit voltage), represented by the letter C. The basic unit of capacitance is the Farad (F). (2) Rated voltage is the maximum DC voltage that can be continuously applied to the capacitor at the minimum and rated ambient temperatures. If the operating voltage exceeds the withstand voltage of the capacitor, the capacitor will break down, causing damage. In practice, as the temperature rises, the withstand voltage value will decrease. (3) Insulation resistance. When DC voltage is applied to a capacitor, leakage current is generated; the ratio of the two is called insulation resistance. When the capacitance is small, its value mainly depends on the surface state of the capacitor. Generally, the higher the insulation resistance, the better. (4) Loss. The energy consumed due to heating per unit time when a capacitor is under the action of an electric field is called loss. Loss is related to frequency range, dielectric medium, conductance, and the resistance of the metal parts of the capacitor. (11) Frequency characteristics. As the frequency increases, the capacitance of general capacitors tends to decrease. When the capacitor operates below its resonant frequency, it exhibits capacitive behavior; when it exceeds its resonant frequency, it exhibits inductive behavior, at which point it is no longer a capacitor but an inductor. Therefore, it is essential to avoid operating the capacitor above its resonant frequency.

Vishay Techno electrical component applications

Metal waveguides and metal resonant cavities are widely used in decimeter waves, centimeter waves, and longer millimeter waves. Since the cross-section of the waveguide and the dimensions of the resonant cavity are close to the wavelength, the dimensions of metal waveguides and resonant cavities are too small and difficult to manufacture. It is even more impossible to apply metal waveguides or resonant cavities in the infrared or visible light bands, where the wavelength is on the order of micrometers. For this reason, dielectric waveguides and dielectric resonators have rapidly developed and gained widespread application. Although the dimensions of dielectric waveguides and dielectric resonators are also on the order of the wavelength, they are easy to fabricate into tiny sizes using microfabrication techniques. For example, optical fibers and optical waveguides with cross-sectional dimensions on the order of micrometers belong to dielectric waveguides. The field in a metal waveguide can be regarded as caused by the reciprocal reflection of plane waves between conductor surfaces, and the field in a dielectric waveguide can also be regarded as caused by the total reflection of electromagnetic waves between dielectric interfaces. Therefore, a dense medium surrounded by a sparse medium forms a dielectric waveguide. In an ideal metal waveguide, the electromagnetic field forms a standing wave transversely, and outside the waveguide boundary, it approximates an ideal conductor with no electromagnetic field. In a dielectric waveguide, the electromagnetic field forms a standing wave transversely, but an electromagnetic field still exists outside the dielectric waveguide, which decreases exponentially transversely, known as the evanescent field. In a metal waveguide filled with a homogeneous medium, the TE mode and TM mode can individually satisfy the short-circuit boundary conditions of the waveguide walls, so the TE mode and TM mode can always be separated, and both can propagate in the metal waveguide. When a metal waveguide is filled with more than two media, or partially filled with dielectric, the electromagnetic field must satisfy not only the boundary conditions on the conductor walls but also the continuity conditions at the media interfaces. In the case of uniform filling with more than two media, only the hybrid HEM mode of TE and TM can exist. After understanding the above content, we can further explore dielectric resonators. As early as 1939, the concept and theory of dielectric resonators were proposed, but due to the lack of suitable dielectric materials, this theory remained dormant for more than 20 years without practical development. By the 20th century, in the 60s, the successful development of high-permittivity ceramics such as rutile ceramic (ε≈80100) brought dielectric resonators back into attention. However, the high temperature coefficient of rutile ceramic limited its practical application. In the 20th century, in the 70s, barium titanate and zirconium titanate ceramics were developed. Their high permittivity, low loss, and low temperature coefficient made dielectric resonators practical. Dielectric resonators have advantages such as small size, light weight, high quality factor, and good stability. They are particularly suitable for application in microstrip circuits, microwave integrated circuits, and millimeter-wave bands, receiving significant attention and developing rapidly. When the permittivity is very high, the interface between the dielectric and air approximates an open circuit, and the reflection coefficient of electromagnetic waves at the interface is close to 5. At this point, the surface of the dielectric resonator can be regarded as an open-circuit wall, i.e., a magnetic wall. Thus, the dielectric resonator becomes a closed system with homogeneous boundary conditions, i.e., an equivalent open-circuit wall (magnetic wall) resonant cavity.

Vishay Techno electrical component principles

In addition to the function of converting optical signals into electrical signals like a photodiode, a phototransistor also has the function of amplifying electrical signals. The appearance of a phototransistor is not much different from that of a general transistor. Generally, a phototransistor only leads out two terminals—the emitter and the collector—while the base is not led out. The casing also has a window to allow light to enter. To increase illumination, the base region area is made large, while the emitter region is small, so incident light is mainly absorbed by the base region. During operation, the collector junction is reverse-biased, and the emitter junction is forward-biased. In the absence of light, the current flowing through the tube is the dark current Iceo = (1 + β) Icbo (very small), which is smaller than the penetration current of a general transistor; when illuminated, a large number of electron-hole pairs are excited, causing the base current Ib to increase. The current flowing through the tube at this moment is called photocurrent, and the emitter current Ie = (7 + β) Ib. It can be seen that a phototransistor has higher sensitivity than a photodiode.

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