A semiconductor is a substance whose electrical properties lie between a metallic conductor and an insulator. It is typically a solid (such as germanium, silicon, and certain compounds), where changes in impurity content and external conditions (such as temperature changes, exposure to light, etc.) can cause changes in its electrical conductivity.

        Currently, semiconductor components include diodes, triodes, field effect transistors, thyristors, Darlington transistors, LEDs, and integrated blocks and chips containing semiconductor tubes.

① Diode:

        Diodes, among electronic components, the most common function of diodes is to only allow current to pass in a single direction (called forward bias), and to block it in reverse (called reverse bias). Therefore, a diode can be thought of as an electronic version of a check valve.

② Transistor:

        An electronic component consisting of three electrodes. There are two types of electronic tube triodes and semiconductor triodes. The electron tube triode consists of a screen electrode, a gate electrode, and a cathode; A semiconductor triode consists of a collector, a base, and an emitter.

③ Field Effect Tube:

        Field effect transistors belong to voltage control elements, which are similar to triodes of electronic tubes, but their construction and operating principles are completely different from those of electronic tubes. Compared to bipolar transistors, field effect transistors have the following characteristics:

        (1) Field effect transistor is a voltage control device that controls ID through UGS;

        (2) The input current of a field effect transistor is very small, so its input resistance is large.

        (3) It uses most carriers to conduct electricity, so its temperature stability is good;

        (4) The voltage amplification coefficient of the amplification circuit composed of the transistor is smaller than the voltage amplification coefficient of the amplification circuit composed of the triode;

        (5) Field effect tubes have strong radiation resistance;

        (6) The noise is low because there is no shot noise caused by minority carrier diffusion in chaotic motion.

④ Thyristors:

        The conduction conditions of the thyristor are: applying a forward voltage and having a trigger current at the gate; Its derivative devices include: fast thyristor, bidirectional thyristor, reverse conduction thyristor, light controlled thyristor, etc. It is a high-power switching semiconductor device, represented by the letter "V" and "VT" in the circuit (the letter "SCR" in the old standard).

⑤ Darlington tube

        Principle of Darlington tube: Darlington tube is also known as composite tube. It connects two transistors together appropriately to form an equivalent new transistor. This is equivalent to the amplification factor of the transistor being the product of the two. Application of Darlington tube:

        (1) Used in high-power switching circuits, motor speed regulation, inverter circuits.

        (2) Driving a small relay uses a CMOS circuit to drive a high sensitivity relay through a Darlington transistor, as shown in the upper right figure. In the dashed box is a low-power NPN Darlington transistor FN020.

        (3) Drive LED intelligent display screen

⑥ LED diode

        Light Emitting Diode (LED) is a semiconductor component. Initially, it is often used as an indicator light, display light emitting diode board, etc; With the emergence of white LEDs, they are also used for lighting.

        LED, known as the fourth generation lighting source or green light source, has the characteristics of energy conservation, environmental protection, long life, small size, and is widely used in various fields such as indication, display, decoration, backlight, general lighting, and urban nightscape.