Vishay Roederstein electrical components German Vishay Roederstein models Vishay Roederstein prices

Vishay Roederstein electrical components include resistors, capacitors, inductors, diodes, transistors, field-effect transistors, thyristors, transformers, relays, sensors...; electronic devices include analog circuits (operational amplifiers, comparators, signal conditioners), logic circuits (flip-flops, counters, decoders, registers, transceivers, NOT gates, AND gates, OR gates, NAND gates, NOR gates, XOR gates), microcontrollers, memory, digital potentiometers, signal conversion circuits (A/D converters, D/A converters, voltage/frequency converters), communication circuits (various interface circuits), monitoring and reset circuits (power supply monitoring, program monitoring)..., too numerous to mention.

Vishay Roederstein electrical component principles

An NPN bipolar transistor can be viewed as two diodes joined together with a common anode. In the normal operating state of a bipolar transistor, the base-emitter junction is forward-biased, while the base-collector junction is reverse-biased. When no external voltage is applied, the electron concentration in the N region of the emitter junction is greater than that in the P region, and some electrons will diffuse into the P region. Similarly, some holes in the P region will also diffuse into the N region. Thus, a space charge region forms at the emitter junction, generating an internal electric field directed from the N region to the P region. This field hinders further diffusion, achieving dynamic equilibrium. At this point, if a forward voltage is applied to the emitter junction, the dynamic balance between carrier diffusion and the internal electric field in the depletion layer is broken, causing thermally excited electrons to inject into the base region. In an NPN transistor, the base region is P-doped, where holes are the majority carriers; therefore, electrons in this region are called "minority carriers." Electrons injected from the emitter into the base region partly recombine with the majority carriers (holes) there. On the other hand, due to the low doping level and thin physical dimensions of the base region, and because the collector junction is reverse-biased, most electrons reach the collector region via drift motion, forming the collector current. To minimize recombination before electrons reach the collector junction, the base region must be made sufficiently thin so that the time required for carrier diffusion is shorter than the lifetime of minority carriers in the semiconductor, and the base thickness must be much smaller than the electron diffusion length. In modern bipolar transistors, the typical base region thickness is a few tenths of a micrometer. It should be noted that although both the collector and emitter are N-doped, their doping levels and physical properties differ; therefore, a bipolar transistor must be distinguished from a configuration of two diodes connected in series in opposite directions.

Vishay Roederstein electrical component principles

A photodiode is a semiconductor device that converts optical signals into electrical signals. Its core is also a PN junction. Compared with ordinary diodes, the structural difference is that the PN junction area is made as large as possible to facilitate incident light reception, the electrode area is kept as small as possible, and the junction depth of the PN junction is very shallow, generally less than 5 micrometers. Photodiodes operate under reverse bias. Without illumination, the reverse current is very small, known as dark current. When illuminated, photons carrying energy enter the PN junction and transfer energy to bound electrons in covalent bonds, causing some electrons to break free from the covalent bonds, thereby generating electron-hole pairs, known as photo-generated carriers. Under the influence of reverse voltage, they participate in drift motion, significantly increasing the reverse current. The greater the light intensity, the larger the reverse current. This characteristic is called "photoconductivity." The current generated by a photodiode under general illumination is called photocurrent. If a load is connected in the external circuit, the load receives an electrical signal that varies correspondingly with changes in light. Photodiodes are widely used photosensitive devices in electronic circuits. Like ordinary diodes, photodiodes have a PN junction. The difference is that the photodiode housing has a transparent window to receive light for photoelectric conversion. In circuit diagrams, the text symbol is generally VD.

Vishay Roederstein electrical component classification

Thyristors have various classification methods: (1) Classification by turn-off, conduction, and control methods: Thyristors can be divided into conventional thyristors, bidirectional thyristors, reverse-conducting thyristors, gate turn-off thyristors, BTG thyristors, temperature-controlled thyristors, and light-controlled thyristors, among others. (2) Classification by pins and polarity: Thyristors can be divided into two-terminal thyristors, three-terminal thyristors, and four-terminal thyristors based on their pins and polarity. (3) Classification by package type: Thyristors can be divided into three types based on their packaging: metal-packaged thyristors, plastic-packaged thyristors, and ceramic-packaged thyristors. Among these, metal-packaged thyristors are further divided into bolt-type, flat-type, and round-case types, among others; plastic-packaged thyristors are divided into types with heat sinks and without heat sinks. (4) Classification by current capacity: Thyristors can be divided into high-power thyristors, medium-power thyristors, and low-power thyristors based on current capacity. Typically, high-power thyristors mostly use metal case packaging, while medium- and low-power thyristors mostly use plastic or ceramic packaging. (5) Classification by turn-off speed: Thyristors can be divided into conventional thyristors and high-frequency (fast) thyristors based on their turn-off speed. (6) Zero-crossing triggering - generally for power regulation, i.e., triggering occurs when the phase of the sinusoidal AC voltage crosses zero. Triggering must occur at the zero-crossing point to conduct the thyristor. (7) Non-zero-crossing triggering - the thyristor can be triggered to conduct regardless of the AC voltage phase. Commonly, this is phase-shift triggering, i.e., changing the output percentage by altering the conduction angle (phase angle) of the sinusoidal AC voltage.

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