Resistance: The blocking effect of the conductor on the current is called resistance. It is represented by the symbol R. The unit is ohm, kiloohm, and megaohm, which are represented by Ω, KΩ, and MΩ, respectively.
Model name of the resistor: The model of the domestic resistor consists of four parts (not applicable to sensitive resistors) 1 main name 2 material 3 classification 4 serial number
Classification of resistors: 1 wire wound resistor 2 thin film resistor: carbon film resistor, synthetic carbon film resistor, metal film resistor, metal oxide film resistor, chemical deposition film resistor, glass glaze film resistor, metal Nitride film resistor 3 solid resistor 4 sensitive resistor: varistor, thermistor, photoresistor, force-sensitive resistor, gas-sensitive resistor, humidity-sensitive resistor.
Resistor resistance indication method:
1. Straight-marking method: The resistance value is marked on the surface of the resistor by the number and unit symbol, and the allowable error is directly expressed by the percentage. If the resistance is not marked, the deviation is ±20%.
2. Text symbol method: A regular combination of Arabic numerals and text symbols is used to represent the nominal resistance value, and the allowable deviation is also represented by a text symbol. The number before the symbol indicates the integer resistance, and the following numbers represent the first decimal resistance and the second decimal resistance. The text symbol text symbol indicating the allowable error: DFGJKM allowable deviation is: ±0.5%±1%±2%±5%±10%±20%
3. Digital method: A three-digit digital representation of the nominal value on the resistor. From left to right, the first and second digits are valid values, and the third digit is the index, which is the number of zeros. The unit is Europe. Deviations are usually indicated by text symbols.
4, color standard method: the nominal resistance and allowable deviation are marked on the surface of the resistor with different color bands or points. Most of the foreign resistors use the color standard method.
Black-0, Brown-1, Red-2, Orange-3, Yellow-4, Green-5, Blue-6, Purple-7, Gray-8, White-9, Gold-±5%, Silver-±10 %, colorless - ± 20%
When the resistance is four-ring, the last ring must be gold or silver, the first two digits are significant digits, the third digit is the power square, and the fourth digit is the deviation.
When the resistance is five rings, the distance between the last ring and the front four rings is larger. The first three digits are significant figures, the fourth digit is the power square, and the fifth digit is the deviation.
Identification of the resistance of the chip resistor: (On the surface of the usual chip resistors, the numbers are identified or represented by letters. The resistance method is as follows.
1. The first and second digits represent the real number of resistors.
2. If the number starting from the third digit is 0, it means tens of ohms (between 10 and 99 ohms): 100 is a resistance of 10 ohms, and 990 is a resistance of 99 ohms.
3. The number starting at the third place is 1 and represents a few hundred ohms (between 100 and 999 ohms). For example, 101 is 100 ohms, 151 is 150 ohms, and 951 is 950 ohms.
4. If the number starting from the third place is 2, it means several thousand ohms (between 1000 and 9999 ohms). For example, 102 is 1K, 152 is 1.5K, and 992 is 9.9K.
5. If the number starting from the third place is 3, it means tens of K (between 10K and 99K). For example, 103 is 10K, 223 is 22K, and 993 is 99K.
6. If the number starting from the third digit is 4, it means several hundred K (between 100K and 999K). For example, 104 is 100K, 204 is 200K, and 854 is 850K.
7. If the number starting from the third digit is 5, it means a few M (between 1M and 9.9). For example, 105 is 1M, 155 is 1.5M, and 955 is 9.5M.
8. If the number starting from the third digit is 6, it means ten M (between 100K and 999K). For example, 106 is 10M\566 and 56M.
9. For the four digits, the first three digits are real numbers, and the fourth digit is a multiple. The 1001 is 1K, the 1002 is 10K, and the 1005 is 10M.
Electronic component knowledge - capacitorCapacitance: A physical quantity that characterizes the ability of a capacitor to hold a charge. The amount of electricity we need to increase the potential difference between the two plates of a capacitor by one volt is called the capacitance of the capacitor. The sign of the capacitor is C. Capacitance is one of the most widely used electronic components in electronic devices. It is widely used in blocking, coupling, bypassing, filtering, tuning loops, energy conversion, control circuits and so on. Capacitance is expressed by C. The capacitance units are Farad (F), Microfarad (uF), and Pefara (pF). 1F=10*6uF=10*12pF
1 Farad (F) = 1000000 microfarad (μF) 1 microfarad (μF) = 1000 nanofarads (nF) = 1,000,000 picofarads (pF)
Capacitor Model Nomenclature: The model of a domestic capacitor is generally composed of four parts (not applicable to pressure sensitive, variable, vacuum capacitors). Names, materials, categories, and serial numbers are represented in turn.
Polarity discrimination method of electrolytic capacitor: It can be measured with a multimeter. Discharge the electrolytic capacitor first, then connect the test leads to the two ends. The swing is large, but it should be noted that the positive pole of the pointer table is the capacitor. The negative pole, the digital meter is reversed, and, between the two measurements, the capacitor must be discharged. (2) Use the length of the pin to distinguish the positive and negative long legs from positive and the short legs to negative; the black block with the mark on the capacitor is negative. There are two semicircles on the position of the capacitor on the PCB, and the pin corresponding to the semicircle of the color is the negative pole.
Classification of capacitors:
According to their polarity, they are divided into two categories: polar capacitors (such as electrolytic capacitors) and non-polar capacitors.
According to the structure, there are three categories: fixed capacitors, variable capacitors, and trimmer capacitors.
According to electrolyte classification: organic dielectric capacitors, inorganic dielectric capacitors, electrolytic capacitors and air dielectric capacitors.
According to the purpose: high frequency bypass, low frequency bypass, filtering, tuning, high frequency coupling, low frequency coupling, small capacitors.
Capacitor capacity indication:
1. Straight standard method: directly marked with numbers and unit symbols. For example, 01uF means 0.01 microfarad, and some capacitors use "R" to indicate a decimal point. For example, R56 represents 0.56 microfarad.
2, the text symbol method: a regular combination of numbers and text symbols to indicate capacity. For example, p10 represents 0.1pF, 1p0 represents 1pF, 6P8 represents 6.8pF, and 2u2 represents 2.2uF.
3, color standard method: the color ring or color point represents the main parameters of the capacitor. The color code of the capacitor is the same as the resistance.
Capacitor deviation glyph: +100%-0--H, +100%-10%--R, +50%-10%--T, +30%-10%--Q, +50%-20% --S, +80%-20%--Z.
Commonly used capacitors: aluminum electrolytic capacitors, tantalum electrolytic capacitors, film capacitors, ceramic capacitors, monolithic capacitors, paper capacitors, trimmer capacitors, ceramic capacitors, glass glaze capacitors, mica and polystyrene dielectric capacitors.
Electronic component knowledge - inductor※Inductor: The inductor coil is wound around the insulating tube by one turn of the wire. The wires are insulated from each other, and the insulating tube can be hollow. It can also contain iron core or magnetic powder core, which is called inductance. Although not used much in electronic production, they are equally important in circuits. Inductors, like capacitors, are also energy storage components that convert electrical energy into magnetic energy and store energy in a magnetic field. The inductor is denoted by the symbol L, and its basic unit is Henry (H), which is commonly used in millihenry (mH).
Inductor classification:
Classified by inductance: fixed inductance, variable inductance.
Classified by winding structure: single layer coil, multilayer coil, honeycomb coil.
Classified according to the properties of the magnetizer: air core coil, ferrite coil, iron core coil, copper core coil.
Classified according to the nature of the work: antenna coil, oscillating coil, choke coil, trap coil, deflection yoke.
Inductor action characteristics: It often works with capacitors to form LC filters, LC oscillators, etc. In addition, people also use the characteristics of the inductor to manufacture the choke, transformer, relay, etc.; the characteristics of the inductor are exactly opposite to the characteristics of the capacitor, which has the characteristic of preventing the passage of alternating current and allowing direct current to pass.
There are many inductive coils on the radio, almost all of which are made of an air-wound coil wrapped in an enameled wire or wound on a skeleton core and a core. There are antenna coils (which are made of enameled wire wound on magnetic bars), intermediate frequency transformers (commonly known as mid-week), input and output transformers, and so on.
Commonly used inductors: single layer coil, honeycomb coil, ferrite core and iron powder core coil, copper core coil, color code inductor, choke (choke), deflection coil
Transformer: It consists of a core and a copper coil wire wound around an insulating skeleton. The insulated copper wire is wound around the plastic skeleton, and each skeleton needs to be wound and input and output two sets of coils. The middle of the coil is insulated with insulating paper. After winding, many core sheets are inserted in the middle of the plastic skeleton. This makes it possible to significantly increase the inductance of the coil. The transformer uses electromagnetic induction to transmit electrical energy from one of its windings to the other. The transformer has an important function in the circuit: coupling the AC signal to block the DC signal, and changing the voltage ratio of the input and output; using the transformer to make the impedance at both ends of the circuit well matched to obtain the maximum transmission signal power.
Relay: It is an electromechanical switch. It uses an enamelled copper wire to wrap a few hundred to several thousand turns on a round iron core. When a current flows through the coil, the round iron core generates a magnetic field and the upper side of the round iron core The iron plate with the contact piece is sucked to open the first contact and turn on the second switch contact. When the coil is de-energized, the core loses its magnetic properties, and due to the elastic action of the contact copper piece, the iron plate leaves the iron core and resumes connection with the first contact. Therefore, it is possible to control the switches of other circuits with a small current. The entire relay is protected by a plastic or plexiglass dust cover, and some are fully sealed to prevent electro-oxidation.
Electronic component knowledge - semiconductor devicesSemiconductor: It is a substance with special properties. It is not completely conductive like a conductor, and it is not electrically conductive like an insulator. It is somewhere in between, so it is called a semiconductor. The two most important elements of semiconductors are silicon (read "gui") and é”— (read "zhe").
Semiconductor classification: Semiconductors are mainly divided into diodes, transistors, thyristors, and integrated circuits.
Diode classification: Zener diodes for voltage regulation, switching diodes for digital circuits, varactor diodes for tuning, and photodiodes, etc. The most commonly seen are LEDs, rectifier diodes... diodes are used in circuits. "D" indicates; the LED is indicated by "LED"; the Zener diode is indicated by "Z".
Diode polarity discrimination:
(1) Ordinary diode: Generally, the polarity is indicated on the outer casing of the diode. Most use a ring of different colors to indicate the negative, and some are directly marked with a "-".
(2) The polarity discrimination of the LED can be judged from the internal structure of the pin and the tube. If the pin is not cut, it is generally believed that the long leg of the LED is positive, the short pin is negative, and the vertical The polarity discrimination of electrolytic capacitors is consistent. From the internal structure of the die, the die is composed of two parts of the large and small lobes. The large lobes have a conical crater for concentrating to increase the brightness. The middle part is connected by a thin metal wire to the two small lobes. Connected to the long-leg positive electrode, the short-legged negative electrode is connected to the large-valve portion of the die.
(3) The multimeter ohm file is used to judge that when the forward conduction is small, the resistance value is small, and the black meter pen is connected to the positive pole of the diode. By the way, he called "black and small, red and big negative."
Detection of common diodes: The polarity of the diode is usually marked on the package. If there is no mark, the forward and reverse resistance can be measured by the multimeter resistance file (usually R&TImes; 100 or &TImes; 1K)
Detection of ordinary light-emitting diodes:
(1) The pointer type multimeter with &TImes; 10kΩ block can be used to roughly judge whether the LED is good or bad. Normally, the forward resistance of the diode is tens to 200 kΩ, and the value of the reverse resistance is âˆ. If the forward resistance value is 0 or ∞, and the reverse resistance value is small or 0, it is easily damaged. This kind of detection method can't see the illumination of the LED tube in real time, because &TImes; 10kΩ block can not provide a large forward current to the LED.
(2) It can accurately measure the light and electric characteristics of LEDs with 3V regulated source or two series of dry cells and multimeter (pointer or digital). To do this, connect the circuit as shown in Figure 10. If the measured VF is between 1.4 and 3V, and the brightness of the light is normal, it can be said that the light is normal. If VF=0 or VF≈3V is measured and does not emit light, the luminous tube is broken.
Detection of infrared light-emitting diodes: Due to infrared light-emitting diodes, it emits infrared light of 1 to 3 μm, which is invisible to the human eye. Usually, the emission power of a single infrared light-emitting diode is only a few mW, and the angular distribution of the luminous intensity of different types of infrared LEDs is also different. The forward voltage drop of an infrared LED is generally 1.3 to 2.5V. Because the infrared light emitted by the human eye is invisible, the detection method of the visible light LED can only determine whether the positive and negative electrical characteristics of the PN junction are normal, and it is impossible to determine whether the illumination condition is normal or not. For this reason, it is best to prepare a photosensor (such as a 2CR, 2DR type silicon photocell) as a receiver. Use a multimeter to measure the change in voltage across the battery. To determine whether the infrared LED emits infrared light after adding an appropriate forward current.
Transistor: A triode is an electronic component consisting of two PN structures with three poles, a base (B) collector (C), and an emitter (E).
Transistor action: The triode mainly acts as a current amplification and switching function in the circuit; it also acts as an isolation.
Triode Name: Chinese Semiconductor Device Model Nomenclature
The semiconductor device model consists of five parts (field effect device, semiconductor special device, composite tube, PIN tube, laser device type, only the third, fourth, and fifth parts).
The first part: the number of effective electrodes of the semiconductor device is represented by numbers. 2-diode, 3-triode
The second part: the material and polarity of the semiconductor device are indicated by Chinese pinyin letters. When indicating a diode: AN type bismuth material, BP type bismuth material, CN type silicon material, DP type silicon material. For the triode: A-PNP type tantalum material, B-NPN type tantalum material, C-PNP type silicon material, D-NPN type silicon material.
The third part: the internal type of the semiconductor device is represented by the Chinese phonetic alphabet. P-common tube, V-microwave tube, W-stabilized tube, C-parameter tube, Z-rectifier tube, L-rectifier stack, S-tunnel tube, N-damper tube, U-optoelectronic device, K-switch tube , X-low frequency small power tube (F "3MHz, Pc "1W", G-high frequency small power tube (f" 3MHz, Pc "1W), D-low frequency high power tube (f "3MHz, Pc" 1W), A-high frequency high power tube (f"3MHz, Pc"1W), T-semiconductor thyristor (controlled rectifier), Y-body effect device, B-avalanche tube, J-step recovery tube, CS-FET , BT-semiconductor special device, FH-composite tube, PIN-PIN tube, JG-laser device.
Part IV: Numbers are represented by numbers. Part 5: Specification numbers are indicated by Chinese Pinyin letters.
For example: 3DG18 represents NPN type silicon material high frequency triode
Triode classification1) NPN and PNP triodes with silicon/germanium material according to material and polarity. 2) According to the power, there are small power triode, medium power triode, high power triode.
3) According to the application, there are high and medium frequency amplification tubes, low frequency amplification tubes, low noise amplification tubes, photoelectric tubes, switch tubes, high back pressure tubes, Darlington tubes, and triode tubes with damping.
4) According to the working frequency, there are low frequency triode, high frequency triode and ultra high frequency triode. 5) According to the production process, there are plane type triode, alloy type triode, and diffusion type triode.
6) According to the different shape and package, it can be divided into metal package triode, glass package triode, ceramic package triode, plastic package triode and so on.
Transistor pin polarity: plug-in pin diagram (1), patch pin diagram (2) The figure below is 9014. Generally, the small and medium power transistors are obeyed in order from left to right (provided that the small and medium power plastic triodes are oriented toward themselves, and the three pins are placed downwards, then ebc from left to right)
Field effect transistor: The MOS field effect transistor is a metal-oxide-semiconductor type field effect transistor, which is abbreviated as MOSFET (Metal-Oxide-Semiconductor Field-Effect-Transistor), and is an insulated gate type.
The basic working principle of a metal oxide semiconductor field effect transistor is to induce a conductive channel in the semiconductor to operate by the electric field effect of the semiconductor surface. When the gate G voltage VG is increased, the majority carriers of the p-type semiconductor surface are gradually reduced and depleted, and the electrons gradually accumulate to the inversion. When the surface reaches the inversion, the electron accumulation layer will form a conductive channel between the n+ source region S and the n+ drain region D. When VDS ≠0, a large current IDS flows between the source and drain electrodes. The gate-source voltage required to bring the semiconductor surface to a strong inversion is called the threshold voltage VT. When VGS VT takes different values, the conductivity of the inversion layer will change, and different IDS will be generated under the same VDS to realize the control of the source-drain current IDS by the gate-source voltage VGS.
Field effect classification: FETs mainly include junction field effect transistors (JFETs) and insulated gate field effect transistors (IGFETs). The substrate (B) of the insulated gate field effect transistor is connected to the source (S), and its three electrodes are a gate (G), a drain (D) and a source (S), respectively. The transistor is divided into an NPN and a PNP tube, and its three poles are a base (b), a collector (c), and an emitter (e). The G, D, and S poles of the FET have similar functions to the b, c, and e poles of the transistor. The difference between the insulated gate effect transistor and the junction field effect transistor is that their conduction mechanism and current control principle are fundamentally different. The junction transistor uses the width variation of the depletion region to change the width of the conductive channel to control the drain current, and the insulation. The gate field effect transistor controls the current by changing the conductive channel by the electric field effect of the semiconductor surface and the amount of the electric induction charge. The difference in their properties makes the junction field effect transistor often used in the amplifier input stage (previous stage), and the insulated gate field effect transistor is used in the final stage of the power amplifier (output stage). The FET works the same as the triode, except that they are voltage-controlled components, one is a current-controlled component, and the FET has only one PN junction, as shown in Figure 1-1.
Precautions and detection methods for field effect classification: MOS FETs are more "squeaky". This is because its input resistance is very high, and the gate-source capacitance is very small, it is easily charged by external electromagnetic field or static electricity, and a small amount of charge can form a relatively high voltage on the interelectrode capacitance (U =Q/C), the tube is damaged. Therefore, each pin is twisted together at the factory, or installed in the metal foil, so that the G pole and the S pole are at the same potential to prevent accumulation of static charge. When the tube is not in use, all leads should be shorted. Care should be taken when measuring and taking appropriate anti-static measures. Before measuring, short the body to ground before touching the MOSFET pins. It is best to connect a wire to the ground on the wrist to keep the human body and the earth at the same potential. Then separate the pins and remove the wires. Set the multimeter to R × 100, first determine the grid. If the resistance of one foot and the other foot is infinite, it is proved that this foot is the gate G. The exchange meter weight measurement, the resistance value between SD should be several hundred ohms to several thousand ohms, of which the smaller the resistance value, the black meter is connected to the D pole, the red meter is connected to the S pole. The 3SK series produced in Japan, the S pole is connected to the tube, and it is easy to determine the S pole. The G pole is suspended, the black meter is connected to the D pole, the red meter is connected to the S pole, and then the G pole is touched with a finger, and the needle should have a large deflection. The dual gate MOS field effect transistor has two gates G1, G2. In order to distinguish, the G1 and G2 poles can be respectively touched by the hand, and the G2 pole is deflected by the hand to the left side. At present, some MOSFET tubes have a protection diode between the GS poles, and it is not necessary to short-circuit each pin at ordinary times. For other related understandings, I will not elaborate, as long as everyone can know.
Integrated circuit: An integrated circuit is a device with a special function that integrates components such as transistors, resistors, and capacitors on a silicon substrate. The English is abbreviated as IC, also known as a chip. It is represented by "U" in the circuit.
Integrated circuit classification: Integrated circuits are divided into two major factions, analog and digital, according to different functional uses, and the specific functions are numerous, and their applications cover all aspects of human life. Integrated circuits are classified into large-scale, medium-scale and small-scale based on internal integration. Its packaging comes in many forms. "Dual in-line" and "single inline" are the most common. Soft-packaged ICs for consumer electronics, and chip-packaged ICs for precision products.
※Notes on the use of integrated circuits: Most ICs use CMOS components as the core integration. For CMOS ICs, special attention should be paid to preventing electrostatic breakdown ICs. It is best not to solder them with ungrounded soldering irons. Also use the IC to pay attention to its parameters, such as operating voltage, heat dissipation, etc. The digital IC uses a working voltage of +5V, and the analog IC operates at different voltages.
Integrated circuit models: There are various types of integrated circuits, and their naming also has certain rules. It is usually composed of a prefix, a number, and a suffix. The prefix indicates the manufacturer and category of the integrated circuit, and the suffix is ​​generally used to indicate the package form, version code, etc. of the integrated circuit. Commonly used integrated circuits such as the low power audio amplifier LM386 are available in a variety of different suffixes. LM386N is a product of National Semiconductor Corporation, LM stands for linear circuit, and N stands for plastic dual in-line. The specific package is not much to explain, as long as we can recognize it. Other single integrated circuits: voltage regulator IC, music IC, voice IC...
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