fli electrical components Germany fli model fli price

fli electrical components are electronic devices made from semiconductor materials (silicon, selenium, germanium, etc.). A diode has two electrodes: the positive electrode, also called the anode; and the negative electrode, also called the cathode. When a forward voltage is applied across the two terminals of the diode, the diode conducts; when a reverse voltage is applied, the diode cuts off. The conduction and cutoff of the diode are equivalent to the closing and opening of a switch. Diodes have unidirectional conductivity; when conducting, the current flows from the anode through the device to the cathode. The diode is one of the earliest semiconductor devices developed, and its applications are very widespread. Especially in various electronic circuits, by reasonably connecting diodes with components such as resistors, capacitors, and inductors to form circuits with different functions, it is possible to achieve AC rectification, demodulation of modulated signals, limiting and clamping, and voltage stabilization of power supply voltages.

fli electrical component structure

The structure and materials of new high-voltage Schottky diodes differ from those of traditional Schottky diodes. Traditional Schottky diodes are formed by metal-semiconductor contact. Metals such as aluminum, gold, molybdenum, nickel, and titanium can be used, while the semiconductor is typically silicon or gallium arsenide. Since electrons have higher mobility than holes, N-type semiconductor material is selected as the substrate to obtain good frequency characteristics. To reduce the junction capacitance of the Schottky diode and increase the reverse breakdown voltage without causing excessive series resistance, a high-resistance N- thin layer is usually epitaxially grown on an N+ substrate. It is well known that there are a large number of conductive electrons inside metal conductors. When metal contacts a semiconductor (with the distance between them only on the order of atomic size), the Fermi level of the metal is lower than that of the semiconductor. At the sub-levels corresponding to the conduction band of the semiconductor inside the metal, the electron density is lower than the electron density in the conduction band of the semiconductor. Therefore, after contact, electrons diffuse from the semiconductor to the metal, causing the metal to become negatively charged and the semiconductor positively charged. Since metal is an ideal conductor, the negative charge is distributed only within a thin layer on the surface with atomic-scale thickness. For N-type semiconductors, the donor impurity atoms that lose electrons become positive ions and are distributed over a larger thickness. The result of electron diffusion from the semiconductor to the metal forms a space charge region, a built-in electric field, and a potential barrier, with the depletion layer located only on the N-type semiconductor side (the entire barrier region falls on the semiconductor side). The direction of the built-in electric field in the barrier region points from the N-type region toward the metal. As thermionic emission increases the built-in field, the drift current, which is opposite to the diffusion current, increases, finally reaching dynamic equilibrium and forming a contact potential barrier between the metal and the semiconductor, known as the Schottky barrier. When the external voltage is zero, the electron diffusion current equals the reverse drift current, achieving dynamic equilibrium. When forward bias is applied (i.e., positive voltage to the metal, negative voltage to the semiconductor), the built-in field is weakened, the barrier on the semiconductor side is lowered, and a forward current from the metal to the semiconductor is formed. When reverse bias is applied, the built-in field is strengthened, the barrier height increases, and a small reverse current from the semiconductor to the metal is formed. Therefore, like SBD and PN junction diodes, it is a nonlinear device with unidirectional conductivity.

fli electrical component principle

In addition to the function of converting optical signals into electrical signals like photodiodes, phototransistors also have the function of amplifying electrical signals. The appearance of a phototransistor is not much different from that of a general transistor. Generally, a phototransistor has only two leads—the emitter and the collector—with the base not brought out. The casing also has a window to allow light to enter. To increase light exposure, the base area is made large, while the emitter area is small, so that 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 general transistors; when illuminated, a large number of electron-hole pairs are generated, causing the base current Ib to increase. The current flowing through the tube at this moment is called the photocurrent, and the emitter current Ie = (2 + β) Ib. It can be seen that phototransistors have higher sensitivity than photodiodes.

fli electrical component principle

The construction of a mercury switch is very simple. The exterior is a sealed cylindrical insulating housing containing approximately one-fifth mercury. Two wires led out from the inside are fixed at one end of the housing. This constitutes a mercury switch. Due to gravity, the mercury droplet flows to the lower part of the container. If it simultaneously contacts both electrodes, the switch closes the circuit, turning the switch on. The shape of the container also affects the conditions under which the mercury droplet contacts the electrodes.

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