Before starting this article, let's first understand what electronic components are.
Electronic components are components of electronic components and small machines and instruments, which are often composed of several parts and can be used in similar products. Often refers to some parts of electrical appliances, radios and meters and other industries, such as capacitors, transistors, spring and spring and other sub-devices, common diodes and so on.
In popular terms, the basic parts used to manufacture or assemble electronic machines can be called components, and components are independent individuals in electronic circuits.
Active and passive components
Active element refers to the element that can stimulate the active function of amplifying, oscillating, controlling current or energy distribution of electrical signal when energy supply is obtained, and even perform data calculation and processing. Active components include a wide variety of transistors, integrated circuits, video tubes and displays.
Passive components relative to active components, refers to the electrical signal can not stimulate amplification, oscillation, etc., the response to the electrical signal is passive obedience, the electrical signal according to the original basic characteristics through the electronic component. The most common resistors, capacitors, inductors, etc., are passive components.
Active components and passive components
Active components correspond to active components. If an electronic component works with an internal power supply present, the device is called an active device and requires energy to perform its specific function. Active devices themselves also consume electrical energy, and high-power active devices are usually equipped with radiators.
The passive component corresponds to the passive component. Resistors, capacitors and inductors have signals in the circuit to complete the specified function, and do not need additional excitation power, so they are called passive devices. Passive devices consume little electrical energy themselves, or convert electrical energy into different forms of other energy.
Discrete components and integrated circuits
In terms of physical structure, circuit function and engineering parameters, active devices can be divided into discrete components and integrated circuits. Discrete components are in contrast to integrated circuits.
integrated circuit (ic, integrated circuit) is a kind of transistors, resistance-capacitance and other components required in a class of circuits and wiring together, produced in a small or several small pieces of semiconductor chips or dielectric substrate, packaged as a whole, with circuit functions of electronic components.
Discrete components refer to individual electronic components such as ordinary resistors, capacitors and transistors, collectively referred to as discrete components. Discrete components are single-function, "minimal" components that no longer have other component functional units.
Circuit type components and connection type components are distinguished
Passive devices in electronic systems can be divided into circuit devices and connection devices according to the circuit function they play.
Identification of commonly used electronic components
1. Resistance
Resistors, which we are used to calling resistors, are one of the most commonly used electronic components in electronic devices. The resistance in the circuit is represented by "r" plus a number, such as: r13 indicates the resistance numbered 13. The main functions of resistance in the circuit are shunt, current limiting, voltage division, bias, filtering (used in combination with capacitors) and impedance matching.
Parameter identification: The unit of resistance is ohms (ω), the unit of magnification is: thousand ohms (kω), megohm (mω) and so on. The conversion method is: 1 megohm (mω) =1000 kilohm (kω) =1000000 euros
There are three kinds of parameter marking methods for resistance, namely direct marking method, color marking method and number marking method.
1, the digital marking method is mainly used for small size circuits such as patches, such as: 472 means 47×100ω is 4.7k; 103 means 10,000 ω (10 followed by three zeros), which is 10kω
2, the color ring annotation method is the most used, the first color ring indicates the largest digit of the resistance value, the second color ring indicates the second digit, the third color ring indicates that there should be several zeros at the end of the resistance value, and the fourth color ring indicates the error of the resistance value.
The relationship between the color code position and the magnification of the resistance is shown in the following table:
2. Capacitance
A capacitor is a component composed of two metal films close together and separated by an insulating material. The capacitor is generally represented by "c" plus a number in the circuit, such as c223 indicating a capacitor numbered 223. The characteristics of the capacitor are mainly to isolate the direct current communication.
There are also two main parameters of capacitors: nominal capacitance and allowable error.
1, the nominal capacitance, refers to the capacitance marked on the capacitor, the size of the capacitance capacity is the size of the can store electrical energy. The blocking effect of capacitance on the AC signal is called the capacitive reactance, which is related to the frequency and capacitance of the AC signal.
Capacitive reactance xc=1/2πfc
(f is the frequency of the AC signal, c is the capacitance capacity)
Identification method: The identification method of capacitance is basically the same as that of resistance, and it is also divided into three kinds: direct marking method, color marking method and number marking method. The basic unit of capacitance is expressed in farads (f), and other units are: millimetres (mf), micromethod (uf), nanomethod (nf), picomethod (pf), where 1 farad =103 millimetres =106 micromethod =109 nanomethod =1012 picomethod.
Direct marking method: large capacity capacitor, its capacity value is directly marked on the capacitor, such as 2200uf /10v.
Letter representation: 152m=1500pf.
Digital representation: Generally use three digits to indicate the size of the capacity, the first two digits indicate the significant number, and the third digit is the multiplier. For example, 102 indicates that 10 x 102 PF is 1000 PF.
2, the allowable error is divided into three levels, and the representation of the resistor error is the same. Trimmer capacitors and variable capacitors mark their minimum and maximum capacities, such as 7/270p
Three, inductance
The inductor coil is made by winding the insulated wire around the insulated skeleton for a certain number of turns. Dc can pass through the coil, the DC resistance is the resistance of the wire itself, the voltage drop is very small; When the AC signal passes through the coil, the coil ends will generate a self-induced electromotive force. The direction of the self-induced electromotive force is opposite to the direction of the applied voltage, which hinders the passage of AC, so the characteristic of the inductor is to pass DC to prevent AC, and the higher the frequency, the greater the coil impedance. The inductor can form an oscillating circuit with the capacitor in the circuit.
Inductance is commonly represented by "l" plus a number in the circuit, such as: l3 indicates the inductance numbered 3.
Inductance generally has a direct marking method and a color marking method, the color marking method is similar to resistance. The basic unit of inductance is: hen (h), and the conversion unit is: 1h=103mh=106uh.
Fourth, crystal diode
The main characteristic of the diode is one-way conductivity, that is, under the action of forward voltage, the on-resistance is very small; Under the action of reverse voltage, the on-resistance is very large or infinite. The crystal diode detects radio waves in the radio, converts alternating current into pulsating direct current in the power supply conversion circuit, and acts as a contactless switch in the digital circuit, all of which make use of its unidirectional conductive characteristics.
Crystal diodes can be divided into: rectifier diode, isolation diode, Schottky diode, light-emitting diode and voltage regulator diode.
1. Identification method:
The identification of the diode is very simple, the n pole (negative electrode) of the small power diode, most of them use a color ring on the surface of the diode, some diodes also use a special symbol for the p pole (positive electrode) or the n pole (negative electrode), and there are symbols for "p" and "n" to determine the polarity of the diode. The positive and negative poles of the LED can be identified from the length of the pin, with the long foot being positive and the short foot being negative.
2. Main parameters
The rated forward working current refers to the maximum forward current value that the diode is allowed to pass when it is working continuously for a long time. Because the current through the tube will make the tube core heat, the temperature rises, the temperature exceeds the allowable limit (silicon tube is about 140, germanium tube is about 90), it will cause the tube core to overheat and damage.
The highest reverse operating voltage, when the reverse voltage added to both ends of the diode is high to a certain value, the tube will be broken down and the unidirectional conductivity will be lost. In order to ensure the safety of use, the maximum reverse operating voltage is specified.
Reverse current refers to the reverse current flowing through the diode under the specified temperature and maximum reverse voltage. The smaller the reverse current, the better the one-way guiding electrical performance of the tube. It is worth noting that the reverse current is closely related to temperature, and about every 10 years the temperature increases, the reverse current doubles.
Five, the transistor
The transistor has the function of amplifying and switching in the circuit. We use the transistor to amplify the weak signal current in the circuit or make an automatic switch to control the on-off of household appliances. The transistor is commonly represented by "q" plus a number in the circuit, such as: q1 indicates the triode numbered 1.
Commonly used transistor packaging form metal packaging and plastic packaging two categories, the pin arrangement has a certain rule. The three poles of the transistor are called the base (b), the collector (c), and the emitter (e), and the arrows on the emitter indicate the direction of the current flowing through the transistor.
Six, integrated circuit
Integrated circuit is the diode, transistor and resistor capacitor and other components in accordance with the requirements of the circuit structure, made on a small piece of semiconductor material to form a complete circuit with certain functions, and then packaged, its text symbol is IC.
Integrated circuits were developed rapidly with the development of electronic technology in the late 1960s. Compared with circuits assembled with discrete components, integrated circuits have many advantages such as fewer components, light weight, small size, good performance and power saving, so the integration of electronic products has become an inevitable trend in the development of electronic technology.
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