# Basic knowledge of the top ten most commonly used electronic components

For engineers in the electronics industry, electronic components, like the rice people eat, need to be touched and used every day. But the truth is, many engineers may not fully understand what's going on inside. Here are ten electronic components commonly used by engineers, along with basic concepts and knowledge. Let's learn about it.

A: the resistance
People say "resistors are the most used component of any electronic circuit. "Resistance, because the material has an obstruction effect on the current, in this effect is called resistance material. Resistance causes a change in electron flux. The lower the resistance, the greater the flux of electrons, and vice versa. Substances with little or no resistance are called conductors, or conductors for short. Substances that cannot form current transmission are called electrical insulators, or insulators for short.

In physics, resistance is used to show how much resistance a conductor has to a current. The greater the resistance of a conductor, the more the conductor obstructs the current. The resistance of different conductors is usually different. Resistance is a property of the conductor itself. Resistance unit is a kind of energy - consuming unit that impedes the movement of water.

The resistance value of a resistive element is generally temperature-dependent. The physical quantity used to measure the effect of temperature is the temperature coefficient, which is defined as the percentage change in the resistance value as the temperature increases by 1℃.

The resistor is represented by "R" plus a number in the circuit. For example, R1 represents the resistor numbered 1. The main functions of resistors in a circuit are shunt, current limiting, voltage divider, offset, etc.

2: capacitance
Capacitance is the amount of charge stored at a given potential difference; The SI unit is Farah (F). Generally, electric charges move in an electric field under the action of a force. When there is a medium between the conductors, it will hinder the movement of charge and cause charge to accumulate on the conductor; The most common example of cumulative charge storage is two parallel metal plates, which are also known as capacitors.

Capacitance is usually represented by a "C" plus a number in the circuit. Capacitance is a component consisting of two metal films that are close together and separated by an insulating material. The main characteristic of capacitance is its separation from DC and AC phases. Capacitance is the amount of electrical energy that can be stored. The resistance of capacitor to AC signal is called capacitor reactance, which is related to the frequency and capacitance of ac signal. The types of capacitors commonly used in telephones are electrolytic capacitors, ceramic capacitors, chip capacitors, monolithic capacitors, tantalum capacitors and polyester capacitors.

Three: crystal diode
Semiconductor terminal devices in solid state electronic devices. The main characteristic of these devices is nonlinear current-voltage characteristics. Since then, with the development of semiconductor materials and technology, a variety of crystal diodes with various structures and different functions have been developed by using different semiconductor materials, doping distribution and geometric structure. Manufacturing materials include germanium, silicon and compound semiconductors. Crystal diodes can be used to generate, control, receive, transform, amplify signals and convert energy.

The main characteristic of a diode is unidirectional conductivity, that is, the conduction resistance is small under the forward voltage and is maximum or infinite under the reverse voltage. Because of the above characteristics, diodes are often used in cordless telephone rectification, isolation, voltage regulation, polarity protection, coding control, FM noise reduction and other circuits. When the digital multimeter is used to measure the diode, the positive pole of the red meter connected to the diode and the negative pole of the black meter connected to the diode is the positive electrode conduction resistance of the diode, and the pointer multimeter pen connection method is just the opposite.

Four: regulated diode
Zener diode, this diode is a semiconductor device with high resistance up to the critical reverse breakdown voltage.

Zener diode is characterized by the breakdown, zener diode voltage at both ends is basically unchanged. When the voltage regulator is connected to the circuit, if the voltage of the power supply fluctuates, or for other reasons causes the voltage at various points in the circuit to change, the voltage at both ends of the load will remain basically the same.

Five: inductance
When a coil passes an electric current, a magnetic field is induced in the coil, which generates an induced current against the current passing through the coil. We call the interaction between the current and the coil the inductance, or inductance, in Henry (h). It can also be used to make inductance components.

Inductance is usually indicated in a circuit by an "L" followed by a number. Induction coils are made by winding insulated wires around an insulating skeleton. Dc can pass through the coil, dc resistance is the resistance of the wire itself, the voltage drop is very small; When ac signals pass through the coil, self-induced electromotive force is generated at both ends of the coil. The direction of the self-induced electromotive force is opposite to the direction of the applied voltage, blocking the passage of the exchange. Thus, inductance is characterized by dc impedance. The higher the frequency, the greater the coil impedance.

Six: varactor diode
Varactor diodes, also known as "variable reactance diodes". It is a diode composed of a PN junction capacitor (barrier capacitor) and its reverse bias Vr. Its structure is shown in the figure below.

The tube varactance diode is a special kind of diode, which is designed according to the principle that the junction capacitance of the "PN junction" in the ordinary diode changes with the change of the applied reverse voltage. Varactric diodes are mainly used in high frequency modulation circuits of mobile phones or fixed-line phones in cordless phones where low frequency signals are modulated to high frequency signals for transmission. In the operating state, the diode modulation voltage is usually applied to the negative electrode, so that the internal junction capacitance of the diode varies with the modulation voltage. Varsity diode failure, mainly for leakage or poor performance :(1) leakage occurs, the high-frequency modulation circuit does not work or modulation performance deterioration. (2) When the performance of the varactor diode deteriorates, the operation of the high frequency modulation circuit is unstable, and the modulated high frequency signal is sent to and received by the other party to produce distortion. When one of the above occurs, the same type of varactor diode should be replaced.

Seven: crystal triode
Crystal triode is one of the basic components of semiconductor. It has current amplification function and is the core component of electronic circuit. Triodes are made of two PN junctions very close to each other on a semiconductor substrate. The two PN junctions divide the bulk semiconductor into three parts, with the base region in the middle and the emitter and collector region on both sides, arranged as PNP and NPN.

Transistors are often represented in a circuit by "Q" plus a number. The transistor is a special device which contains two PN junctions and has the ability of amplification.

Eight: field effect tube
The acronym field effect transistor is FET. Conductors involve most conduction, also known as unipolar transistors. It is a voltage controlled semiconductor device. It has high input resistance (108~109 ω), low noise, low power consumption, large dynamic range, easy integration, no secondary breakdown, wide safety work area, etc. It has become a powerful bipolar and power transistor. Competitors.

Fets have the advantages of high input impedance and low noise, and have been widely used in various electronic devices. Especially when the field-effect transistor is used as the input stage of the entire electronic device, the performance of ordinary transistors is difficult to achieve.

Fets are divided into junction type and insulated door type, and their control principles are the same.

Ix. Sensors
A sensor is a physical device or biological organ that can detect and sense external signals, physical conditions (such as light, heat, humidity) or chemical components, and transmit the detected information to other devices or organs.

The definition of sensor in national standard GB 7665-87 is: "a device or device that can sense the specified measured component and convert it into usable signals according to certain rules, usually consisting of a sensitive element and a conversion element". Meet the requirements of information transmission, processing, storage, display, recording and control. This is the first step to realize automatic detection and automatic control.

In the new Webster dictionary, "sensor" is defined as "a device that receives power from one system and usually transmits it in another form to a device in a second system." According to this definition, the function of a sensor is to convert one form of energy into another form of energy, so many scholars also call a sensor a sensor.

Ten: transformer
Transformer is a device that changes ac voltage using electromagnetic induction principle. The main components are a coil, two coil and iron core. In electrical equipment and wireless circuits, it is commonly used for voltage lifting, impedance matching and safety isolation.

In a generator, a potential can be induced in the coil, whether the coil is moved through a magnetic field or through a fixed coil. In both cases, the value of magnetic flux is constant, but the amount of magnetic flux intersecting the coil is variable, which is the principle of mutual inductance. A transformer is a device that uses electromagnetic mutual inductance to convert voltage, current, and impedance. The functions of the transformer mainly include: voltage conversion; Current conversion, impedance conversion; Isolation; Voltage regulation.