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wilhelm huber electrical component is a current-limiting element. After connecting a resistor in the circuit, the resistance value is fixed, typically with two pins, and it can limit the current magnitude through the branch to which it is connected. Resistors with unchangeable resistance values are called fixed resistors. Those with variable resistance values are called potentiometers or variable resistors. An ideal resistor is linear, meaning the instantaneous current through the resistor is proportional to the applied instantaneous voltage. Variable resistors used for voltage division. On the exposed resistive body, one or two movable metal contacts are tightly pressed. The contact position determines the resistance between either end of the resistive body and the contact. It is a two-terminal device where terminal voltage and current have a definite functional relationship, reflecting the ability to convert electrical energy into other forms, represented by the letter R, with the unit Ohm Ω. Actual devices such as light bulbs, heating wires, and resistors can all be represented as resistor elements. The resistance value of a resistive element is generally related to temperature, material, length, and cross-sectional area. The physical quantity measuring the extent to which resistance is affected by temperature is the temperature coefficient, defined as the percentage change in resistance value when the temperature rises by 1 ℃. The main physical characteristic of resistance is the conversion of electrical energy into thermal energy; it can also be said to be a dissipative element, generating internal energy when current passes through it. Resistors usually serve the functions of voltage division and current shunting in circuits. For signals, both AC and DC signals can pass through resistors.

wilhelm huber electrical component parameters

The main parameters of transistors include current amplification factor, dissipation power, frequency characteristics, maximum collector current, maximum reverse voltage, and reverse current. Amplification factor: The DC current amplification factor, also known as the static current amplification factor or DC amplification ratio, refers to the ratio of the transistor collector current to the base current when there is no changing signal input in the static state. AC amplification factor: The AC amplification factor, also known as the AC current amplification factor or dynamic current amplification factor, refers to the ratio of the change in transistor collector current to the change in base current under AC conditions. Dissipation power: Dissipation power, also known as the maximum allowable collector dissipation power PCM, refers to the maximum collector dissipation power when the transistor parameter changes do not exceed the specified allowable values. Dissipation power is closely related to the transistor's maximum allowable junction temperature and maximum collector current. When using a transistor, its actual power consumption must not exceed the PCM value, otherwise, the transistor will be damaged due to overload. When the transistor's operating frequency exceeds the cutoff frequency, its current amplification factor value will decrease as the frequency increases. The maximum oscillation frequency refers to the frequency at which the transistor's power gain drops to 5. Typically, the maximum oscillation frequency of high-frequency transistors is lower than the common-base cutoff frequency, while the characteristic frequency is higher than the common-base cutoff frequency and lower than the common-collector cutoff frequency. Maximum current: The maximum collector current refers to the maximum current allowed to pass through the transistor collector. Maximum reverse voltage: The maximum reverse voltage refers to the highest operating voltage allowed to be applied to the transistor during operation. It includes the collector-emitter reverse breakdown voltage, collector-base reverse breakdown voltage, and emitter-base reverse breakdown voltage. Collector reverse breakdown voltage refers to the maximum allowable reverse voltage between the collector and emitter when the transistor base is open. Base reverse breakdown voltage refers to the maximum allowable reverse voltage between the collector and base when the transistor emitter is open. Emitter reverse breakdown voltage refers to the maximum allowable reverse voltage between the emitter and base when the transistor collector is open. The reverse current between the bases, also known as the collector junction reverse leakage current, refers to the reverse current between the collector and base when the transistor emitter is open. The reverse breakdown current between the emitters refers to the reverse leakage current between the collector and emitter when the transistor base is open, also known as the penetration current. The smaller this current value, the better the transistor performance.

wilhelm huber electrical component principle

An NPN type 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 on the emitter junction, generating an internal electric field directed from the N region to the P region. This field hinders the further occurrence of the aforementioned diffusion process, thereby achieving dynamic equilibrium. At this point, if a forward voltage is applied to the emitter junction, the dynamic equilibrium between the carrier diffusion motion and the internal electric field in the depletion layer will be broken, causing thermally excited electrons to inject into the base region. In an NPN type transistor, the base region is P type doped, where holes are the majority dopants, so electrons in this region are called "minority carriers." Electrons injected from the emitter into the base region partly recombine with the majority carriers (holes) here. 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 will reach the collector region via drift motion, forming the collector current. To mitigate electron recombination before reaching the collector junction, the base region of the transistor must be made sufficiently thin so that the time required for carrier diffusion is shorter than the lifetime of semiconductor minority carriers, and the base thickness must be much smaller than the electron diffusion length. In modern bipolar transistors, the typical thickness of the base region is a few tenths of a micron. It should be noted that although both the collector and emitter are N type doped, their doping levels and physical properties are not identical. Therefore, a bipolar transistor must be distinguished from a configuration of two diodes connected in series in opposite directions.

wilhelm huber electrical component applications

Thermistors can also be used as electronic circuit components for temperature compensation in instrument circuits and cold-junction temperature compensation for thermocouples. Utilizing the self-heating characteristics of NTC thermistors enables automatic gain control, constituting RC oscillator amplitude stabilization circuits, delay circuits, and protection circuits. When the self-heating temperature is much higher than the ambient temperature, the resistance value is also related to the heat dissipation conditions of the environment. Therefore, this characteristic of thermistors is often utilized in flow meters, gas analyzers, and thermal conductivity analysis to create specialized detection elements. PTC thermistors are mainly used for overheat protection of electrical equipment, contactless relays, constant temperature control, automatic gain control, motor starting, time delay, automatic degaussing of color TVs, fire alarms, and temperature compensation. Main disadvantages: (1) The relationship between resistance value and temperature is severely nonlinear; (2) Poor consistency and interchangeability of components; (3) Components are prone to aging and have poor stability; (4) Except for special high-temperature thermistors, the vast majority of thermistors are only suitable for the 0～153 ℃ range, which must be noted during use.

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