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SEHILL electrical components are semiconductor triodes, also known as bipolar junction transistors or crystal triodes. They are semiconductor devices that control current. Their function is to amplify weak signals into electrical signals with larger amplitudes, and they are also used as contactless switches. The triode is one of the basic semiconductor components, featuring current amplification capability, and is a core component in electronic circuits. A triode is formed by creating two closely spaced PN junctions on a single semiconductor substrate. These two PN junctions divide the entire semiconductor into three parts: the middle part is the base region, and the two sides are the emitter region and the collector region. There are two arrangement types: PNP and NPN.

SEHILL electrical component principle

Like ordinary diodes, light-emitting diodes (LEDs) consist of a PN junction and exhibit unidirectional conductivity. When a forward voltage is applied to an LED, holes injected from the P region into the N region and electrons injected from the N region into the P region recombine with electrons in the N region and holes in the P region, respectively, within a few micrometers near the PN junction, producing spontaneous radiation fluorescence. The energy states of electrons and holes differ among various semiconductor materials. The amount of energy released during electron-hole recombination varies; the greater the energy released, the shorter the wavelength of the emitted light. Commonly used LEDs emit red, green, or yellow light. The reverse breakdown voltage of an LED is greater than 13 volts. Its forward volt-ampere characteristic curve is very steep, so a current-limiting resistor must be connected in series to control the current through the diode. The core part of an LED consists of a wafer made of P-type semiconductor and N-type semiconductor. Between the P-type and N-type semiconductors lies a transition layer called the PN junction. In the PN junction of certain semiconductor materials, when injected minority carriers recombine with majority carriers, excess energy is released in the form of light, thereby directly converting electrical energy into light energy. When a reverse voltage is applied to the PN junction, minority carriers are difficult to inject, so no light is emitted. When it operates in the forward state (i.e., a forward voltage is applied across its terminals), current flows from the LED anode to the cathode, causing the semiconductor crystal to emit light of various colors ranging from ultraviolet to infrared. The intensity of the light is related to the current.

SEHILL electrical component types

For different application scenarios, the purpose of using varistors varies, and the voltage/current applied to the varistor differs accordingly. Therefore, the requirements for varistors also vary. Distinguishing these differences is crucial for correct usage. Based on the purpose of use, varistors can be divided into two main categories: (1) protection varistors and (2) circuit function varistors. Protection resistors: (1) Distinguish whether the varistor is for power supply protection or for signal line and data line protection, as they must meet different technical standard requirements. (2) Based on the different continuous operating voltages applied to the varistor, varistors used across power lines can be classified into AC type or DC type. Varistors exhibit different aging characteristics under these two types of voltage stress. (3) Based on the different abnormal overvoltage characteristics withstandable by the varistor, varistors can be classified into three types: surge suppression type, high-power type, and high-energy type. 1. Surge suppression type varistors refer to varistors used to suppress transient overvoltages such as lightning overvoltage and switching overvoltage. The occurrence of such transient overvoltages is random and non-periodic, and the peak current and voltage values can be very high. The vast majority of varistors belong to this category. 2. High-power type varistors refer to varistors used to absorb periodic continuous pulse groups, such as varistors connected in parallel to switching power supply converters. Here, the impulse voltage occurs periodically with a known period, and the energy value can generally be calculated. Although the peak voltage is not very high, the average power is considerable due to the high frequency of occurrence. 13. High-energy type varistors refer to varistors used to absorb magnetic energy in large inductive coils such as generator excitation coils and lifting electromagnet coils. For such applications, the main technical indicator is energy absorption capacity. The protective function of varistors can be repeated multiple times in most application scenarios, but sometimes they are designed as "one-time" protective devices similar to current fuses. For example, varistors with short-circuit contacts connected in parallel to the loads of certain current transformers.

SEHILL electrical component principle

Crystal triodes are divided into two types based on material: germanium tubes and silicon tubes. Each type has two structural forms: NPN and PNP. However, the most commonly used triodes are silicon NPN and germanium PNP. (Here, N means negative; N-type semiconductor is formed by adding phosphorus to high-purity silicon to replace some silicon atoms, generating free electrons for conduction under voltage stimulation. P means positive; boron is added to replace silicon, creating a large number of holes to facilitate conduction.) Apart from the difference in power supply polarity, their working principles are identical. The following introduces only the current amplification principle of NPN silicon tubes. An NPN tube consists of 7 pieces of N-type semiconductor sandwiching a piece of P-type semiconductor. The PN junction formed between the emitter region and the base region is called the emitter junction, while the PN junction formed between the collector region and the base region is called the collector junction. The three leads are called the emitter e, base b, and collector c, respectively. When the potential at point b is higher than the potential at point e by a fraction of a volt, the emitter junction is in a forward-biased state. When the potential at point C is higher than the potential at point b by several volts, the collector junction is in a reverse-biased state, and the collector power supply Ec must be higher than the base power supply Eb. During triode manufacturing, the majority carrier concentration in the emitter region is intentionally made higher than that in the base region. Meanwhile, the base region is made very thin, and the impurity content is strictly controlled. Thus, once the power is connected, due to the forward bias of the emitter junction, the majority carriers (electrons) in the emitter region and the majority carriers (holes) in the base region easily diffuse across the emitter junction toward each other. However, since the former's concentration is significantly higher than the latter's, the current passing through the emitter junction is basically an electron flow, referred to as the emitter electron flow.

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