Working in the electronics industry, I have a special connection with all kinds of electronic components . For engineers in the electronics field, electronic components are like rice—something we encounter and use every day. However, many engineers may not fully understand the intricacies involved. Here, I've listed ten commonly used electronic components by engineers in the electronics industry, along with related basic concepts and knowledge, for a quick review.
Celebrity 1: Resistance
As someone working in the electronics industry, everyone knows about resistors. Their importance is undeniable. It's often said that "resistors are the most frequently used component in all electronic circuits."
Resistance is the resistance a material exerts on the flow of electric current, hence the name "resistive material" based on this resistance. Resistance causes a change in the amount of electrons that can pass through the body; the lower the resistance, the greater the electron flow, and vice versa. Materials with no resistance or very low resistance are called electrical conductors, or simply conductors. Materials that cannot conduct electric current are called electrical insulators, or simply insulators.
In physics, resistance is used to represent the magnitude of a conductor's opposition to the flow of electric current. The greater the resistance of a conductor, the greater its opposition to the flow of current. Different conductors generally have different resistances; resistance is an inherent property of the conductor itself. A resistive element is an energy-consuming component that impedes the flow of electric current.
The resistance value of a resistive element is generally related to temperature. The physical quantity that measures the extent to which resistance is affected by temperature is the temperature coefficient, which is defined as the percentage change in resistance value when the temperature rises by 1°C.
In circuits, resistors are represented by "R" followed by a number, such as R1 representing resistor number 1. The main functions of resistors in circuits are current shunting, current limiting, voltage division, and biasing.
1. Parameter Identification: The unit of resistance is ohm (Ω), and multiplier units include kiloohms (KΩ) and megaohms (MΩ). The conversion method is: 1 megaohm = 1000 kiloohms = 1000000 ohms. There are three methods for marking resistor parameters: direct marking, color code marking, and numerical marking. a. Numerical marking is mainly used for small-volume circuits such as surface mount devices, for example: 472 represents 47 × 100Ω (i.e., 4.7K); 104 represents 100K. b. Color code marking is the most commonly used, and examples are as follows: four-color band resistors and five-color band resistors (precision resistors).
2. The color code positions and multiplier relationships of the resistors are shown in the table below: Color Significant Digits Multiplier Allowable Deviation (%) Silver / x 0.01 ± 10 Gold / x 0.1 ± 5 Black 0 + 0 / Brown 1 x 10 ± 1 Red 2 x 100 ± 2 Orange 3 x 1000 / Yellow 4 x 10000 / Green 5 x 100000 ± 0.5 Blue 6 x 1000000 ± 0.2 Purple 7 x 10000000 ± 0.1 Gray 8 x 100000000 / White 9 x 1000000000 /
Star 2: Capacitor
Capacitance (or charge capacity) refers to the amount of electric charge stored at a given potential difference; it is denoted by C, and the SI unit is the farad (F). Generally, electric charges move under the influence of an electric field. When a dielectric material is placed between conductors, it impedes the movement of charges, causing them to accumulate on the conductors; this accumulation and storage of charge is most commonly seen in two parallel metal plates. It is also the common name for a capacitor.
1. Capacitors in circuits are generally represented by "C" followed by a number (e.g., C13 represents capacitor number 13). A capacitor is a component consisting of two metal films placed close together, separated by an insulating material. The primary characteristic of a capacitor is to block direct current (DC) and pass alternating current (AC). The capacitance value indicates the amount of electrical energy it can store. The impedance of a capacitor to AC signals is called capacitive reactance, which is related to the frequency of the AC signal and the capacitance. Capacitive reactance XC = 1/2πfc (where f represents the frequency of the AC signal and C represents the capacitance). Commonly used capacitor types in telephones include electrolytic capacitors, ceramic capacitors, surface mount capacitors, monolithic capacitors, tantalum capacitors, and polyester capacitors. Please visit: Power Transmission and Distribution Equipment Network for more information.
2. Identification Methods: The identification methods for capacitors are basically the same as those for resistors, including direct marking, color coding, and numerical marking. The basic unit of capacitance is the farad (F). Other units include millifarads (mF), microfarads (uF), nanofarads (nF), and picofarads (pF). Where: 1 farad = 10³ millifarads = 10⁶ microfarads = 10⁹ nanofarads = 10¹² picofarads. Larger capacitors have their capacitance value directly marked on the capacitor, such as 10uF/16V. Smaller capacitors have their capacitance value represented by letters or numbers. Letter representation: 1m = 1000uF, 1P² = 1.2pF, 1n = 1000pF. Numerical representation: Generally, three digits are used to represent the capacitance; the first two digits represent significant figures, and the third digit is the multiplier. For example: 102 means 10 × 102pF = 1000pF; 224 means 22 × 104pF = 0.22uF. 3. Capacitor capacitance error table: Symbol FGJKLM. Allowable error: ±1% ±2% ±5% ±10% ±15% ±20%. For example: A ceramic capacitor labeled 104J indicates a capacitance of 0.1uF and an error of ±5%.
Star 3: Crystal Diode
A crystal diode is a two-terminal semiconductor device in solid-state electronic devices. These devices are primarily characterized by nonlinear current-voltage characteristics. Subsequently, with the development of semiconductor materials and processing technology, various crystal diodes with diverse structures and functions have been developed using different semiconductor materials, doping distributions, and geometries. Manufacturing materials include germanium, silicon, and compound semiconductors. Crystal diodes can be used to generate, control, receive, convert, and amplify signals, and perform energy conversion.
In circuits, crystal diodes are often represented by "D" followed by a number, such as D5, which represents diode number 5.
1. Function: The main characteristic of a diode is unidirectional conductivity, meaning that its on-resistance is very small under forward voltage and extremely large or infinite under reverse voltage. Because of these characteristics, diodes are commonly used in cordless phones for rectification, isolation, voltage regulation, polarity protection, encoding control, FM modulation, and noise reduction circuits. The crystal diodes used in telephones can be categorized by their function as: rectifier diodes (such as 1N4004), isolation diodes (such as 1N4148), Schottky diodes (such as BAT85), light-emitting diodes (LEDs), and Zener diodes.
2. Identification Methods: Identifying diodes is simple. For low-power diodes, the N-terminal (negative) is usually marked with a colored ring on the diode's exterior. Some diodes also use special diode symbols to indicate the P-terminal (positive) or N-terminal (negative). Others use the symbols "P" and "N" to determine the diode's polarity. The positive and negative terminals of an LED can be identified by the length of its leads: the longer lead is positive, and the shorter lead is negative.
3. Testing Precautions: When using a digital multimeter to test a diode, connect the red probe to the positive terminal of the diode and the black probe to the negative terminal. The resistance value measured under these conditions is the forward conduction resistance of the diode. This is exactly the opposite of the probe connection method for an analog multimeter.
4. The voltage rating of commonly used 1N4000 series diodes is compared as follows: Model 1N4001 1N4002 1N4003 1N4004 1N4005 1N4006 1N4007 Voltage Rating (V) 50 100 200 400 600 800 1000 Current (A) All are 1.
Star 4: Zener Diode
A Zener diode (also called a Zener diode) is a semiconductor device that has a high resistance up to the critical reverse breakdown voltage.
Zener diodes are often represented in circuits by "ZD" followed by a number, such as ZD5, which represents Zener diode number 5.
1. The voltage regulation principle of a Zener diode: The characteristic of a Zener diode is that after it breaks down, the voltage across its terminals remains essentially constant. Therefore, when a Zener diode is connected to a circuit, if the power supply voltage fluctuates or other factors cause voltage variations at different points in the circuit, the voltage across the load will remain essentially constant.
2. Fault Characteristics: The main faults of Zener diodes are open circuit, short circuit, and unstable voltage regulation. Of these three faults, the first manifests as an increase in power supply voltage; the latter two manifest as a drop in power supply voltage to zero volts or unstable output. Commonly used Zener diode models and their voltage regulation values are shown in the table below: Model 1 N4728 1 N4729 1 N4730 1 N4732 1 N4733 1 N4734 1 N4735 1 N4744 1 N4750 1 N4751 1 N4761 Voltage Regulation Value 3.3V 3.6V 3.9V 4.7V 5.1V 5.6V 6.2V 15V 27V 30V 75V.
Star 5: Inductor
Inductance: When current flows through a coil, a magnetic field is induced within the coil. This induced magnetic field, in turn, generates an induced current that opposes the current flowing through the coil. This interaction between the current and the coil is called inductive reactance, or inductance, and its unit is the "Henry". This property can also be used to make inductive components.
Inductance is commonly represented in circuits by "L" followed by a number, such as L6, which indicates inductor number 6. An inductor coil is made by winding insulated wire a certain number of turns around an insulated frame. Direct current (DC) can pass through the coil; the DC resistance is simply the resistance of the wire itself, resulting in a very small voltage drop. When an alternating current (AC) signal passes through the coil, a self-induced electromotive force (EMF) is generated across the coil. This EMF is in the opposite direction to the applied voltage, impeding the passage of AC. Therefore, the characteristic of an inductor is that it passes DC and blocks AC; the higher the frequency, the greater the coil impedance. Inductors can be used in conjunction with capacitors to form resonant circuits. Inductors are generally marked using either a direct marking method or a color code method, similar to that used for resistors. For example, brown, black, gold, gold indicates a 1uH inductor (5% tolerance).
The basic unit of inductance is the Henry (H). Conversion units are: 1H = 10³mH = 10⁶uH.
Star Item 6: Varactor Diode
A varactor diode, also known as a "variable reactance diode," is a type of diode that utilizes the relationship and principle between the PN junction capacitance (barrier capacitance) and its reverse bias voltage Vr. Its structure is shown in the figure on the right.
A varactor diode is a special type of diode designed based on the principle that the junction capacitance of the "PN junction" inside a regular diode changes with the applied reverse voltage. In cordless phones, varactor diodes are mainly used in the high-frequency modulation circuit of the mobile phone or landline to modulate low-frequency signals onto high-frequency signals and transmit them. In operation, the modulation voltage of the varactor diode is generally applied to the negative terminal, causing the internal junction capacitance of the varactor diode to change with the modulation voltage. When a varactor diode malfunctions, it mainly manifests as leakage or deterioration in performance: (1) When leakage occurs, the high-frequency modulation circuit will not work or the modulation performance will deteriorate. (2) When the varactor performance deteriorates, the high-frequency modulation circuit will be unstable, causing distortion in the high-frequency signal sent to the other party and received by the other party. If any of the above situations occur, a varactor diode of the same model should be replaced.
Star 7: Transistor
A transistor is one of the basic semiconductor components, providing current amplification and serving as a core element in electronic circuits. A transistor is made by creating two closely spaced PN junctions on a semiconductor substrate. These two PN junctions divide the semiconductor into three parts: the middle part is the base region, and the two outer parts are the emitter and collector regions. There are two common transistor arrangements: PNP and NPN.
Transistors are often represented in circuits by "Q" followed by a number, such as Q17, which represents transistor number 17.
1. Characteristics: A transistor (or simply transistor) is a special device containing two PN junctions and possessing amplification capability. It comes in two types: NPN and PNP. These two types of transistors can complement each other in terms of operating characteristics; the so-called "paired transistors" in an OTL circuit are PNP and NPN transistors used together. Commonly used PNP transistors in telephones include models such as A92 and 9015; NPN transistors include models such as A42, 9014, 9018, 9013, and 9012.
2. Transistors are mainly used in amplifier circuits for amplification. There are three common connection methods in common circuits. For ease of comparison, the characteristics of the three transistor connection methods are listed in the table below for your reference. Name | Common Emitter Circuit | Common Collector Circuit (Emitter Follower) | Common Base Circuit | Input Impedance | Medium (hundreds to thousands of ohms) | Large (tens of kilohms and above) | Small (several ohms to tens of ohms) | Output Impedance | Medium (thousands to tens of kilohms) | Small (several ohms to tens of ohms) | Large (tens of kilohms to hundreds of kilohms) | Voltage Amplification Factor | Large (less than 1 and close to 1) | Large | Current Amplification Factor | Large (tens) | Large (tens) | Small (less than 1 and close to 1) | Power Amplification Factor | Large (approximately 30-40 dB) | Small (approximately 10 dB) | Medium (approximately 15-20 dB) | Frequency Characteristics | High Frequency Difference | Good | Continued Table | Applications | Intermediate stage of multi-stage amplifiers, low-frequency amplification input stage, output stage, or impedance matching; high-frequency or wideband circuits and constant current source circuits.
Star 8: Field Effect Transistor
A field-effect transistor (FET) is a type of unipolar transistor that conducts electricity using majority carriers. It is a voltage-controlled semiconductor device. It boasts advantages such as high input resistance (10⁸–10⁹ Ω), low noise, low power consumption, wide dynamic range, ease of integration, no secondary breakdown, and a wide safe operating area. It has become a strong competitor to bipolar transistors and power transistors.
1. Field-effect transistors (FETs) have advantages such as high input impedance and low noise, and are therefore widely used in various electronic devices. In particular, using FETs as the input stage of an entire electronic device can achieve performance that is difficult to achieve with conventional transistors.
2. Field-effect transistors (FETs) are divided into two main categories: junction type and insulated-gate type, but their control principles are the same.
3. Comparison of Field-Effect Transistors and Transistors
(1) Field-effect transistors are voltage-controlled devices, while transistors are current-controlled devices. Field-effect transistors should be selected when only a small amount of current can be drawn from the signal source; while transistors should be selected when the signal voltage is low and a larger amount of current can be drawn from the signal source.
(2) Field-effect transistors (FETs) conduct electricity using majority carriers, so they are called unipolar devices, while transistors conduct electricity using both majority and minority carriers. They are called bipolar devices.
(3) Some field-effect transistors have interchangeable source and drain terminals, and the gate voltage can be positive or negative, making them more flexible than transistors.
(4) Field-effect transistors can operate under very small current and very low voltage conditions, and their manufacturing process can easily integrate many field-effect transistors on a silicon wafer. Therefore, field-effect transistors have been widely used in large-scale integrated circuits.
Star Nine: Sensors
A sensor is a physical device or biological organ that can detect and sense external signals, physical conditions (such as light, heat, and humidity) or chemical composition (such as smoke), and transmit the detected information to other devices or organs.
The national standard GB7665-87 defines a sensor as: "A device or apparatus that can sense a specified measurand and convert it into a usable signal according to a certain rule, usually composed of a sensing element and a conversion element." A sensor is a detection device that can sense the information being measured and convert that information into an electrical signal or other required form of information output according to a certain rule, to meet the requirements of information transmission, processing, storage, display, recording, and control. It is the primary link in realizing automatic detection and automatic control.
The new Webster's Dictionary defines a "sensor" as:
"To receive power from one system and then send that power to devices in a second system in another form."
According to this definition, the role of a sensor is to convert one form of energy into another, so many scholars also use "transducer" to refer to "sensor".
Star 10: Transformer
A transformer is a device that uses the principle of electromagnetic induction to change alternating current voltage. Its main components are a primary coil, a secondary coil, and an iron core (magnetic core). In electrical equipment and wireless circuits, it is commonly used for voltage step-up/step-down, impedance matching, and safety isolation. In a generator, whether the coil moves through a magnetic field or the magnetic field moves through a stationary coil, an electromotive force is induced in the coil. In both cases, the value of the magnetic flux remains unchanged, but the number of magnetic fluxes linked to the coil changes; this is the principle of mutual induction. A transformer is a device that uses electromagnetic mutual induction to transform voltage, current, and impedance. The main functions of a transformer include: voltage transformation; current transformation; impedance transformation; isolation; and voltage stabilization (magnetic saturation transformer).
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