Ⅰ、What are the classifications of electronic components?
    Electronic components can be classified according to different classification criteria. The following are some common classification methods:
01Classified by function:
    Active components: such as transistors, integrated circuits, etc., are components capable of amplifying, switching, and controlling current or voltage.
    Passive components: such as resistors, capacitors, inductors, etc., which cannot amplify or control current or voltage and are mainly used to limit, store or transmit electrical energy.
02Classified by materials:
    Semiconductor components: such as diodes, transistors, integrated circuits, etc., utilize the characteristics of semiconductor materials to control current or voltage.
    Electronic vacuum tubes: such as electron tubes, phototubes, etc., use the electron flow in a vacuum to control current or voltage.
    Resistors: such as fixed resistors, variable resistors, etc., utilize the characteristics of resistive materials to limit current or voltage.
    Capacitors, such as electrolytic capacitors and ceramic capacitors, utilize the characteristics of dielectrics to store and release electrical energy.
    Inductors, such as coils and transformers, store and transmit electrical energy based on the principle of electromagnetic induction.
03Classified by packaging form:
    Chip packaging: such as SMD packaging, BGA packaging, etc., to make electronic components in the form of chips, which is convenient for integration and soldering.
    Through-hole packaging: such as DIP packaging, TO packaging, etc., which are inserted into sockets through pins or soldered onto circuit boards.
    Pad packaging: such as QFN packaging, LGA packaging, etc., which are soldered and connected to the circuit board through pads.
04Classified by working frequency:
    Low-frequency components: Applicable to low-frequency circuits, such as power supply circuits, audio circuits, etc.
    High-frequency components: Applicable to high-frequency circuits, such as RF circuits, communication circuits, etc.
    These are just some common classification methods. In fact, there are many classifications of electronic components. Different classification methods can be used to select appropriate components based on different needs and applications.

Ⅱ、Common electronic components
01Resistance
    Resistors are the most widely used components in all electronic circuits. As workers in the electronics industry, resistors are well-known to all, and their importance is beyond doubt.
    Resistance, because of the hindering effect of a substance on an electric current, is called the resistive substance under that effect. Resistance will cause changes in the electron flux. The smaller the resistance, the greater the electron flux, and vice versa. A substance that has no resistance or very little resistance is called an electrical conductor, or simply a conductor. Substances that cannot form electric current transmission are called electrical insulators, or simply insulators.
    In physics, Resistance is used to represent the extent to which a conductor hinders current. The greater the resistance of a conductor, the greater the hindrance it exerts on the current. Different conductors generally have different resistances. Resistance is a characteristic of the conductor itself. A resistive element is an energy-consuming component that hinders current.
    Resistance symbol: In a circuit, resistance is represented by "R" followed by a number. For example, R1 indicates the resistor with the number 1. The main functions of a resistor in a circuit include current division, current limiting, voltage division, and biasing, etc.
02Capacitor
    Capacitance refers to the amount of electric charge stored under a given potential difference. It is denoted as C, and the international unit is the farad (F).
    Generally speaking, electric charges will be subjected to force and move in an electric field. When there is a medium between conductors, it hinders the movement of electric charges, causing them to accumulate on the conductors. The most common example of the accumulation and storage of electric charge is two parallel metal plates, which is also commonly known as a capacitor.
03Inductance
    Inductance: When current passes through a coil, a magnetic field induction is formed within the coil. The induced magnetic field then generates an induced current to resist the current passing through the coil. We call the interaction between this current and the coil the inductive reactance of electricity, that is, the inductance, with the unit of "Henry" (H). This property can also be utilized to make inductive components.
    Inductors in circuits are commonly represented by "L" followed by a number. For example, "L6" indicates the inductor with the number 6. An inductance coil is made by winding insulated wires a certain number of turns on an insulated frame. Direct current can pass through a coil. The direct current resistance is the resistance of the wire itself, and the voltage drop is very small. When an alternating current signal passes through a coil, a self-induced electromotive force will be generated at both ends of the coil. The direction of the self-induced electromotive force is opposite to that of the applied voltage, hindering the passage of alternating current. Therefore, the characteristic of an inductor is to allow direct current and resist alternating current. The higher the frequency, the greater the impedance of the coil. An inductor can be combined with a capacitor to form an oscillation circuit in a circuit. Inductors generally have direct marking method and color marking method. The color marking method is similar to that of resistors. For example, brown, black, gold and gold represent an inductance of 1uH (with an error of 5%).
    The basic unit of inductance is: Henry (H). The conversion units are: 1H=103mH=106uH.
04Crystal diode
    A crystaldiode (Crystal Diode) is a semiconductor terminal device in solid-state electronic devices. The main feature of these devices is that they have nonlinear current-voltage characteristics.
    Since then, with the development of semiconductor materials and process technologies, a wide variety of crystal diodes with diverse structures and functions have been developed by using different semiconductor materials, doping distributions and geometric structures. The manufacturing materials include germanium, silicon and compound semiconductors. Crystal diodes can be used to generate, control, receive, transform, amplify signals and perform energy conversion, etc.
    Crystal diode symbol: In circuits, crystal diodes are commonly represented by "D" followed by a number, for example, D5 indicates the diode with the number 5.
05Crystal triode
    A transistor is a semiconductor device that controls current and can amplify it. Its function is to amplify weak signals into electrical signals with larger amplitude values. It is also used as a contactless switch to control various electronic circuits.
    A transistor is made by fabricating two PN junctions that are very close to each other on a semiconductor substrate. The two PN junctions divide the semiconductor block 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 methods: PNP and NPN.
    The symbol of a crystal transistor: In circuits, a crystal transistor is usually represented by "Q" followed by a number. For example, Q17 indicates the transistor with the number 17.