venta electrical components Germany venta model venta price

venta electrical component is a varactor diode, also known as a "variable reactance diode," which is made using the characteristic that the junction capacitance of a PN junction changes with the applied voltage when reverse-biased. As the reverse bias voltage increases, the junction capacitance decreases; conversely, the junction capacitance increases. The capacitance of a varactor diode is generally small, with a maximum value ranging from tens of pF to hundreds of pF. It is mainly used in high-frequency circuits for automatic tuning, frequency modulation, and phase adjustment, for example, as a variable capacitor in the tuning circuit of a television receiver. The main parameters are: zero-bias junction capacitance, zero-bias quality factor, reverse breakdown voltage, center reverse bias voltage, nominal capacitance, capacitance variation range (in picofarads), and cutoff frequency.

venta electrical component structure

The commonly used device is the unidirectional thyristor, also known as the ordinary thyristor. It consists of four layers of semiconductor material and has three PN junctions, with three external electrodes: the electrode drawn from the first layer of P-type semiconductor is called the anode A; the electrode drawn from the third layer of P-type semiconductor is called the gate G; and the electrode drawn from the fourth layer of N-type semiconductor is called the cathode K. As seen from the circuit symbol of the thyristor, it is a unidirectional conductive device like a diode, but with the addition of a gate G, which gives it operating characteristics completely different from those of a diode. The P1N1P2N2 four-layer, three-terminal device, based on silicon monocrystal, is internationally known as the silicon controlled rectifier because its characteristics are similar to those of a vacuum thyratron, abbreviated as thyristor T. Since thyristors were initially used in static rectification, they are also called silicon controlled rectifiers, abbreviated as SCR SCR. In terms of performance, the SCR not only has unidirectional conductivity but also possesses controllability that is more valuable than that of silicon rectifier elements (commonly known as "dead silicon"). It has only two states: conduction and blocking. An SCR can control high-power electromechanical equipment with milliampere-level current. If this power is exceeded, the switching loss of the component increases significantly, and the allowable average current decreases; in this case, the rated current should be derated. SCRs have many advantages, such as controlling high power with low power, with power amplification factors reaching hundreds of thousands of times; extremely fast response, turning on and off within microseconds; contactless operation, no sparks, no noise; high efficiency, low cost, etc. The weaknesses of SCRs include poor static and dynamic overload capacity and susceptibility to interference leading to false triggering. SCRs are mainly classified by appearance into bolt-type, flat-type, and flat-bottom types. Structure of SCR components. Regardless of the shape of the SCR, their cores consist of a four-layer P1N1P2N2 structure composed of P-type silicon and N-type silicon. It has three PN junctions (J1, J2, J3). The anode A is drawn from the P1 layer of the J1 structure, the cathode K is drawn from the N2 layer, and the gate G is drawn from the P3 layer, making it a four-layer, three-terminal semiconductor device.

venta electrical component principle

When two different conductors or semiconductors A and B form a loop with their ends connected, as long as the temperatures at the two junctions are different, with one end at temperature T (called the working end or hot end) and the other end at temperature T0 (called the free end or cold end), an electromotive force (EMF) will be generated in the loop. The direction and magnitude of this EMF depend on the materials of the conductors and the temperatures of the two junctions. This phenomenon is called the "thermoelectric effect," the loop formed by the two conductors is called a "thermocouple," the two conductors are called "thermoelectrodes," and the generated EMF is called "thermoelectric EMF." The thermoelectric EMF consists of two parts: the contact EMF between the two conductors and the temperature difference EMF of a single conductor. The magnitude of the thermoelectric EMF in a thermocouple loop depends only on the conductor materials forming the thermocouple and the temperatures of the two junctions, and is independent of the shape and dimensions of the thermocouple. Once the materials of the two thermocouple electrodes are fixed, the thermoelectric EMF is the functional difference between the temperatures t and t0 of the two junctions. This relationship is widely used in practical temperature measurement. Because the cold end t0 is constant, the thermoelectric EMF generated by the thermocouple changes only with the temperature of the hot end (measurement end), meaning a specific thermoelectric EMF corresponds to a specific temperature. We can achieve temperature measurement simply by measuring the thermoelectric EMF. The basic principle of thermocouple temperature measurement is that two conductors of different compositions form a closed loop. When there is a temperature gradient between the two ends, current flows through the loop, creating an EMF between the ends—the thermoelectric EMF. This is the so-called Seebeck effect. Two homogeneous conductors of different compositions serve as thermoelectrodes; the end with the higher temperature is the working end, and the end with the lower temperature is the free end, which is usually kept at a constant temperature. Based on the functional relationship between thermoelectric EMF and temperature, thermocouple graduation tables are created. These tables are obtained under the condition that the free end temperature is 4 °C. Different thermocouples have different graduation tables. When a third metal material is introduced into the thermocouple loop, as long as the temperatures at the two junctions of this material are the same, the thermoelectric potential generated by the thermocouple remains unchanged, i.e., it is not affected by the introduction of the third metal into the loop. Therefore, during thermocouple temperature measurement, a measuring instrument can be connected. After measuring the thermoelectric EMF, the temperature of the measured medium can be determined. Thermocouple temperature measurement requires that the temperature of the cold end (the measurement end is the hot end; the end connected to the measurement circuit via lead wires is called the cold end) remains constant, so that the thermoelectric potential is proportional to the measured temperature. If the (ambient) temperature of the cold end changes during measurement, it will seriously affect the accuracy of the measurement. Taking certain measures at the cold end to compensate for the effects caused by changes in cold end temperature is called thermocouple cold junction compensation. Special compensation wires are used to connect to the measuring instrument. Calculation methods for thermocouple cold junction compensation: (1) From millivolts to temperature: Measure the cold end temperature, convert it to the corresponding millivolt value, add it to the millivolt value of the thermocouple, and convert to temperature; (2) From temperature to millivolts: Measure the actual temperature and the cold end temperature, convert them separately to millivolt values, subtract to obtain the millivolt value, and thus determine the temperature.

venta electrical component principle

A crystal diode is a p-n junction formed by p-type semiconductor and n-type semiconductor. A space charge layer is formed on both sides of its interface, establishing a built-in electric field. When no external voltage is applied, the diffusion current caused by the carrier concentration difference across the p-n junction and the drift current caused by the built-in electric field are equal, resulting in an electrical equilibrium state. When a forward voltage bias is applied externally, the mutual cancellation of the external electric field and the built-in electric field increases the diffusion current of carriers, causing a forward current. When a reverse voltage bias is applied externally, the external electric field and the built-in electric field are further strengthened, forming a reverse saturation current within a certain reverse voltage range that is independent of the reverse bias voltage value. When the applied reverse voltage reaches a certain level, the electric field strength in the space charge layer of the p-n junction reaches a critical value, causing a carrier multiplication process. This generates a large number of electron-hole pairs, resulting in a large reverse breakdown current, known as the diode breakdown phenomenon.

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