Common basic knowledge of electronic components

Electronic components - general knowledge of common electronic components - KIA electronic components

1、 Resistor

Short for resistance, it refers to the components with certain technical performance that play a role of resistance in the circuit, which can be used to regulate the current and voltage in the circuit, or as a load in the circuit.

1. Parameters of resistance:

A. Resistance value: refers to the value of resistance. 0 Ω - hundreds of M Ω

B. Dissipated power: refers to the maximum power that the resistance can withstand (consume) during long-term operation.

2. Material of resistance:

Commonly used materials for resistance include carbon film, metal film, metal oxide film, wire wound, cement (ceramic) wire wound semiconductor and other materials.

3. Type of resistance:

① Fixed resistance: resistance with fixed resistance value

② Trimming resistance: refers to the resistance whose value can be fine-tuned

③ Adjustable resistance: commonly known as potentiometer, refers to the resistance with continuously adjustable resistance value

④ Thermistor: refers to the resistance whose value changes with temperature

A. Positive temperature coefficient thermistor: refers to the resistance (PTC) whose resistance value increases with temperature rise

B. Negative temperature coefficient thermistor: refers to the resistance whose value decreases with the increase of temperature

⑤ Varistor: refers to the resistance whose value changes with the change of voltage.

⑥ Humidity resistance: refers to the resistance whose value changes with temperature

⑦ Photosensitive resistance: refers to the resistance whose value changes with temperature

⑧ Power representation of resistance: Generally, high-power (more than 3W) resistors are marked with their power values on the resistance housing, such as 3W, 5W, 7W, 10W, 20W, 30W, etc., while low-power (less than 3W) resistors are partially marked with power (such as 3W, 2W, 1W, etc.), and those without power are mostly low-power resistors with power less than 1W. For practical use, high-power resistors can be used to replace low-power resistors, and vice versa, they cannot be replaced, If the resistance power is not known, it can be replaced by the same or slightly larger resistance in practical application.

5. The resistance value of resistance is expressed as follows:

① Directly indicate the value and unit of resistance, such as 1.5 Ω, 160 Ω, 1 Ω, etc.

② Directly mark the resistance value and omit the unit "Ω", such as 100=100 Ω, 1=1 Ω, 22M=22M Ω.

③ Use the number of X to indicate the number of Ω, for example, 4 Ω 7, 9 Ω 1 is 9.1 Ω, 8M2 is 8.2M Ω, etc.

Some use the number of R to represent the number of Ω, such as 1R5=1.5 Ω, 3R9=3.9 Ω, etc.

④ If there are other English letters (such as J, K, M, etc.) or Roman numerals (I, II, III) or positive and negative percentages (such as ± 5%, ± 10%, ± 20%) after the resistance value, it indicates the error level of the resistance.

⑤ Digital representation method (this method is used for chip resistance, partial trimming resistance and potentiometer)

The first and second digits represent the effective number, and the third digit represents the multiplier (1 is 101, 2 is 102, 3 is 103, 4 is 104,...... 8 is 108, but 9 is 100). Multiply the effective number by the multiplier, which is the resistance value. (Unit: Ω)

⑥ Color ring representation:

6. Color ring resistance

The resistance that represents resistance and error with color ring is called color ring resistance

① Four-color ring resistance (common resistance, most used)

The first and second color rings represent the effective number, the third color ring represents the multiplier, and the fourth color ring represents the error

▲ Because of the manufacturing error of the resistance value, the measurement error of the multimeter, and the error of the human eye, it is allowed to measure the resistance value with the multimeter with a certain error, and the error within the range is considered normal.

▲ When measuring the resistance with high resistance (RX10K or 1K), the reading will obviously decrease and the measurement error will increase.

▲ For four-color ring resistance: the first two color rings represent the effective number, which is the first two digits of the resistance value, and the multiplier is the multiple of the resistance value, so read (write) the effective number of the first two color rings, and then multiply the multiplier to obtain the resistance value.

▲ During practice, the resistance value of the color ring resistance can be read out according to the color ring reading, and then tested with the multimeter resistance range. If the test value is basically the same as the reading value (error), then you can see that the color ring is basically accurate. If the measured value and the reading value differ too much, then the color of some color rings may be wrong, and you should retest and look again until it is accurate.

▲ Low resistance gear (X10 or X1) shall be used to test the small resistance value, while high resistance gear (X10K or X1K) shall be used to test the large resistance value. Medium resistance gear (such as X1K, X100, X10, etc.) can be used to test the small resistance value, but the gauge needle refers to the left and right position near the scale. At this time, it is not only easy to see the reading but also the most accurate reading.

▲ Quick reading of four-color ring resistance

② Five-color ring resistance (precision resistance, mostly used in instruments or circuits with high requirements)

The first, second, and third color rings are the effective number, the fourth color ring is the multiplier, and the fifth color ring is the error (note: this color ring is mostly gold, silver, or far away from other color rings). Multiply the effective number by the multiplier to get the resistance value (unit: Ω)

7. Judgment of resistance

① For common fixed resistance, it is normal to test its resistance value with the multimeter resistance gear, which should be basically the same as the nominal value of the resistance (that is, the resistance value indicated on the resistance) (error<± 20%). If the difference between the resistance values is too large (that is, the error is>± 20%), the resistance has changed (that is, it has become larger or smaller, and the resistance value has become larger, while the resistance value has become smaller, which is rare) and cannot be used. If the resistance value has changed to infinity (∞), the resistance has been open circuit damaged. If the resistance value has changed to zero (very rare), the resistance has been short circuit damaged.

② For trimming resistance (also known as trimming potentiometer) and adjustable resistance (also known as potentiometer), it is normal to test the resistance values at both ends of the resistor with a multimeter resistance gear, which should be basically the same as the nominal value (error<± 20%), otherwise the potentiometer is defective or damaged. At the same time, the resistance value between the center head (middle pin) of the test potentiometer and either end should be continuously adjustable from zero to the nominal value, otherwise the potentiometer is defective or damaged.

③ For positive temperature system thermistor (PTC), its resistance value should be about dozens at normal temperature, which is normal. If the resistance value is too large, the internal contact is poor. If the resistance value is infinite, it is open circuit damage. If the resistance value is basically zero, it is short circuit damage. At the same time, when the resistance is energized and heated, its resistance value will become as large (more than several hundred K Ω), which is normal.

④ For negative temperature coefficient thermistors, the resistance value tested at normal temperature should be basically the same as its nominal value (error), which is normal. If the resistance difference is too large, the resistance is poor or damaged. If the resistance value becomes infinite, the resistance is open and damaged. At the same time, the higher the resistance temperature is, the smaller the resistance value is, and the lower the temperature is, the greater the resistance value becomes. Otherwise, the negative temperature coefficient thermistor is poor or damaged.

⑤ For the varistor, because its working voltage is higher (more than tens of V), it is normal to use the multimeter resistance range to test its resistance value to be infinite (because the battery voltage in the meter is low), otherwise the varistor is poor or damaged. When the varistor is below a certain rated voltage, the resistance value is large (generally infinite), and only when it is large to or exceeds its rated voltage can its resistance value be reduced steadily.

⑥ For humidity sensitive resistance, its resistance value should be reduced (about tens of K Ω) when tested in dry air; However, when there is no strong light, its resistance becomes smaller (less than tens of Ω), which is normal. Otherwise, the photosensitive resistor is poor or damaged.

8. Fault and maintenance of resistance

① For the fixed resistance of thin film (such as carbon film, metal film, etc.) materials, if it is damaged, it cannot be repaired, but can only be replaced.

② For wire wound resistors, open circuit faults often occur. At this time, the resistance wire is burnt at a certain position, and the broken part can be used after welding. If it is a cement (wire wound) resistor, open the shell to find the broken part, repair it, and then dry it with cement. Of course, it is better to replace it.

③ For the fine-tuning resistor, it is easy to cause the failure of poor contact between the middle sliding contact and the carbon film due to oxidation. At this time, the potentiometer cleaner is used to clean it. If the cleaning is invalid, it can only be replaced.

④ For the potentiometer, it is easy to wear the carbon film and cause the poor contact of the intermediate sliding plate (center tap). At this time, the position between the central sliding plate and the carbon film can be adjusted or the potentiometer cleaner can be used to clean it.

⑤ For the positive temperature coefficient thermistor (PTC), the fault of poor contact between the resistance and the pressing piece is most likely to occur. At this time, the pressing piece can be adjusted and cleaned for repair. If the resistance body is broken, it cannot be repaired, but can only be replaced.

⑥ For the negative temperature coefficient thermistor, if it is damaged, it cannot be repaired but replaced.

⑦ For the varistor and photosensitive resistor, if it is damaged, it cannot be repaired but replaced.

⑧ For the humidity sensitive resistor, if it is damaged, it can only be replaced, which is difficult to repair. But for the humidity sensitive resistor of video recorder, video camera (DV), etc., if it is damaged and there is no component replacement, it can be replaced by a fixed resistor of about 2 kiloohm in case of emergency. At this time, the humidity detection function will be lost.

2、 Capacitor

Short for capacitance, it is composed of a dielectric layer (insulation layer) between two or two groups of balanced metal plates. It is a device that can store electric charges and has the characteristics of charging and discharging.

1. Dielectric material of capacitor

Common dielectric materials include air, ceramics, mica, polyester, polypropylene, aluminum, silver, and electrolyte.

2. Main electrical parameters of capacitor

① Capacity: refers to the capacity to store electric charges.

The basic unit of capacity is farad, which is abbreviated as method (F). The common units are milli (mF), microf (uF), nano-f (nF), microf (pF), etc.

② Withstand voltage: refers to the voltage that the capacitor can withstand when working for a long time. Withstand voltage: several V-several KV

3. Type of capacitance

① Fixed non-polar capacitance

It refers to the fixed non-polar capacitance, such as ceramic (ceramic dielectric) capacitance, mica capacitance, film capacitance (such as polyester, polypropylene, etc.)

② Fine tuning (non-polarity) capacitance

It refers to the non-polar capacitance with adjustable electrical capacity. (Note: the fine-tuning capacitance is non-polar capacitance). Such as air ceramic, thin film and other fine tuning capacitors.

③ Adjustable capacitance

It refers to non-polar capacitance with continuously adjustable (variable) electrical capacity (note: adjustable capacitance is non-polar capacitance). Such as: air, film and other adjustable capacitors. The common ones are single-connected, double-connected and four-connected adjustable (variable) capacitors.

④ Electrolytic capacitor

It refers to the capacitance using aluminum, tantalum, niobium and other electrolytes as the dielectric, which is called electrolytic capacitor. Most electrolytic capacitors are polar capacitors.

Note: Electrolytic capacitors have no fine-tuning and adjustable structure, and are all capacitors with fixed capacity.

4. Withstand voltage representation of capacitance

① Directly indicate the withstand voltage value and unit. For example: (6V, 25V, 50V, 100V, etc.)

(Note: electrolytic capacitor generally adopts this method, and other capacitors are seldom used)

② Mark the withstand voltage value directly and omit the unit (V). For example, 25 means 25V, 63 means 63V, 100 means 100V, etc

③ The withstand voltage value is represented by numbers and letters, consisting of a number and a letter. The number represents the multiplier of withstand voltage 10, and the letter represents the effective number of withstand voltage. Multiplying the effective number by the multiplier is the withstand voltage value of this capacitor.

(Note: This method is more common for polyester capacitors, and less for other capacitors)

Example: 1A=10V 2A=100V 2B=125V

2C=160V 3D=2KV 3G=4KV

1E=25V 2F=315V 4W=45KV

④ Use color to indicate pressure resistance

Some ceramic dielectric capacitors have colors to indicate their withstand voltage values, that is, different colors on the surface indicate different withstand voltage values

⑤ Some imported ceramic dielectric (ceramic) capacitors with a horizontal line below the capacity are 50V withstand voltage, and those without a horizontal line are 500V withstand voltage.

⑥ The withstand voltage unit of some capacitors is WV for V, such as 50WV for 50V, 350WV for 350V, etc.

⑦ If the withstand voltage value is not indicated by the above method, the capacitance can be considered as a low-voltage capacitance with withstand voltage of 25V (or less).

5. Capacitance representation

① Directly indicate the value and unit of capacity, such as 5PF, 33PF, 100PF, 22nf, 0.01uF, 47uF, 22F, etc.

(Note: most electrolytic capacitors use this method)

② Directly indicate the value of capacity, and the unit is u, n, p to indicate uF, nF, pF, for example, 47u is 47Uf.

③ The number of X stands for the number of X, such as 8P2, 8.2Pf, 6n8, 6.8Nf, 4u7, 4.7uF, etc.

④ Generally, the capacitance value is expressed by the zero point or the dot without indicating the unit. Its capacity value unit is a few tenths of uF, such as 0.01 or 0.01 uF.

⑤ The capacitance value is an integer without indicating the unit. Its unit is PF (note: the last digit of three digits is not zero). For example, 3 is 3PF, 15 is 15PF, 120 is 120PF, etc.

⑥ Digital representation: expressed with three digits (note: the last digit is zero), the first and second digits represent the effective number, and the third digit represents the multiplier (1 is 101, 2 is 102, 3 is 103... 8 is 108, but 9 is 100). Multiply the effective number by the multiplier, which is the capacitance, and its unit is PF.

⑦ Color ring (color bar) representation

Same as color ring resistance, but in PF

⑧ The capacitance capacity unit of the manufacturer is in capital English MDF or MF for uF. For example, 25MDF means 25uF, 100MF means 100uF.

⑨ Some capacitors with letters or positive and negative percentage after the capacitance value are the error level of the capacitance.

Note: The capacitance error level of most manufacturers is expressed by the above letters, but there are also other letters or characters for individual manufacturers. The error level is not listed here.

6. Polarity differentiation of electrolytic capacitors with polarity

① For the aluminum electrolytic capacitor without cutting the leg, the long leg end is positive and the short leg end is negative.

② The positive and negative poles (either positive or negative, or only positive or negative) of the polar capacitor are required to be marked before leaving the factory, which can be directly seen from the shell of the capacitor.

③ Use the multimeter resistance range to test the positive and negative poles (for reference only). Use the highest range range range (RX1K or 10K) of the multimeter resistance range to test the positive and negative leakage resistance (i.e. high insulation resistance) of the polar electrolytic capacitor, while the reverse leakage resistance is large (i.e. low insulation resistance). When testing, the needle first swings to the right (the larger the capacity, the greater the needle swing), and then slowly moves back to the left. If the meter needle can return to infinity (the starting position on the left of the scale), the capacitance basically has no leakage. If the meter needle cannot return to infinity and stops at a certain scale, then the resistance value at this time is the leakage resistance (insulation resistance), which is tested repeatedly (the probe should be replaced) to test its positive and negative leakage (insulation resistance). In case of low leakage (i.e. high insulation resistance), the electrode connected with the black lead is the positive electrode of the electrolytic capacitor and the red lead is the negative electrode. Otherwise, the polarity of the probe is just the opposite.

Note: The black lead is connected to the positive pole of the electrolytic capacitor and the red lead is connected to the negative pole to test the forward leakage resistance.

The red lead is connected to the negative electrode of the electrolytic capacitor and the black lead is connected to the positive electrode to test the negative leakage resistance.

7. Capacitance withstand voltage test

The withstand voltage of the capacitor can be directly seen from the appearance of the capacitor without testing, but it can also be directly tested with a withstand meter if there is one.

8. Capacitance test

① For the qualified capacitor, its capacity is the mark value on the capacitor shell, which can be seen directly without testing.

② If there is a capacitance meter (some digital multimeter can also test the capacitance capacity, but only small capacitance capacity can be tested, not large capacitance capacity). Then the capacitance can be directly measured with a capacitance meter.

③ Some pointer multimeters can also measure their capacitance when connected in series with a certain voltage value of alternating current, but the error is relatively large, which is not recommended.

④ The capacity of the capacitance can also be roughly measured by using the ordinary mechanical pointer multimeter. The method is to use the resistance range of the multimeter (high resistance range for small capacity, and low resistance range for large capacity). If the probe is replaced and tested several times, the larger the electrical capacity, the greater the swing amplitude of the needle, and the smaller the capacity, the smaller the swing amplitude of the needle. Compare the swing amplitude of the needle with its standard capacitance, The capacity of the capacitor can be estimated (note: in general, the capacity of the capacitor used does not need to be particularly accurate, and its capacity can be used normally only within a certain range. In general, the capacitance can be roughly tested when using an ordinary pointer multimeter).

Note: When the high resistance gear is used to test the large capacity, the gauge needle will be marked with an over-scale line and it is difficult to compare the capacity. At this time, the capacity can only be compared by reducing the range test to the limit that the gauge needle is not marked with an over-scale.

▲ If the capacity is too small (less than 0.01uF), there is the highest resistance range for testing to see that the needle swing is normal. For these capacitors, it is difficult to compare their capacity with the resistance range, and only the capacitance meter is used for testing

▲ If the meter needle stops at zero ohm during the test and cannot return, then the capacitance has been short circuited and damaged, and its capacity cannot be tested

9. Capacitive reactance

The equivalent resistance of capacitance to alternating current is called capacitive reactance.

10. Characteristics of capacitance

It has the characteristics of high frequency resistance low frequency and AC resistance DC.

a) Purpose of capacitor

It can be used for filtering, coupling, decoupling, bypass, tuning, resonance and other purposes.

b) Judgment of capacitance

Use a multimeter to judge the resistance gear (high resistance gear must be used for small capacity and low resistance gear can be used for large capacity) When testing the capacitance (the probe should be replaced for many times or the capacitance should be tested after short circuit discharge), the larger the swing amplitude of the probe is, and the swing of the probe should slowly return to normal (that is, the capacitance is good only in this way). If the swing amplitude of the meter needle is too small and does not swing at all when compared with the capacitance with good capacity, the capacity of the capacitance has become smaller or failed to be damaged. At the same time, the swing of the meter needle should be slowly returned (the return speed of small capacity is fast, while the return speed of large capacity is slow). If the needle returns to a certain position and stops, the current resistance is the leakage resistance of the capacitor. The larger the leakage resistance is, the better it is (preferably infinite). If the leakage resistance is too small, the leakage resistance of the capacitor is too large and the performance is poor. If the leakage resistance is basically zero (that is, the meter needle stops at zero ohm on the scale), the capacitor has been short-circuited (broken) and damaged. It is normal to see the swing of the meter needle at the highest level of the resistance range for capacitors with small capacity. However, if the capacitor has leakage or breakdown short circuit, it may be tested (note: for leakage or breakdown short circuit of such capacitor, it can be considered that the capacitor has poor performance or damage and should not be used)

① For non-polar capacitance with a capacity greater than 1uF, it should be obvious that it is normal to move back to infinity quickly after the meter needle swings to the right when testing with the RX1K or 10K gear of the resistance gear of the multimeter. If it cannot be returned to the infinite position, the capacitor has leakage and it is better not to use it. If the leakage resistance is basically zero, the capacitor has been broken through and damaged by short circuit.

② For non-polar capacitance with a capacity greater than 0.01uF (10uF) but less than 1uF, use the highest range of resistance gear (preferably RX10K gear, some capacitance in X1K gear is difficult to observe). During the test, it should be able to see that the meter needle swings slightly (that is, the meter needle swings very small), and then quickly return to the infinity position and set it as normal, and there should be no leakage or short circuit, otherwise the capacitance is poor or damaged.

③ For non-polar capacitance with capacity less than 0.01uF (10nF, i.e. 10000pF), it is normal to use the highest range of the resistance range of the multimeter (for example, it is difficult to see the needle swing during the test (because the capacity is too small, the capacitance has been charged when the probe just touches the capacitance, but the needle can not swing). If it is suspected that the capacity of these capacitors becomes smaller or fails to be damaged, it can only be judged by using the capacitance meter test or the substitution method (substitution method) in practical application, that is, using a good one to replace the suspected damaged one). These capacitors must not have leakage power and short circuit during the test, otherwise it can be considered that the capacitors have been damaged and cannot be used again.

④ For the polar electrolytic capacitor, due to its large capacity, the appropriate gear range can be selected according to the size of the capacity for testing (that is, the small capacity can be used in high gear and the large capacity can be used in low gear, for example, X10K or X1K gear can be used below 10uF, X1K or X100 gear can be used around 100uF, X100 or below 1000uF can be used, RX10 or above 1000uF can be used, and the above gear selection is for reference). The larger the capacity, the greater the needle swing. (Compare the range at the same gear position) and the needle should slowly return to normal after swinging. If the meter needle returns to a certain scale position and stops but cannot return to infinity (i.e., the starting position of the meter needle scale), it indicates that the capacitance has leakage. The smaller the leakage (i.e., the larger the leakage resistance), the better. If the leakage is too large (i.e., the smaller the leakage resistance), the poor performance of the capacitance is. If the leakage resistance is basically zero, the capacitance has been broken down and damaged. At the same time, the electrolytic capacitor has the characteristics of small forward leakage (large leakage resistance) and large reverse leakage (small leakage resistance). Therefore, the normal forward leakage of the test can be small, while the reverse leakage size can not be considered. Also, for the polar electrolytic capacitor, if the storage time is too long, its leakage will also become larger, as long as it is used for a period of time or even tested for many times, its leakage will also become smaller.

3、 Inductor

Referred to as inductance, commonly known as coil, is an inductive component made of coil.

1. Type of inductor

① Air-core inductance: refers to the inductance formed by winding the coil on the hollow support or directly.

② Magnetic core inductance: refers to the coil winding on the magnetic core (i.e. there is a magnetic core inside the coil).

③ Copper core inductance: refers to the inductance of the coil wound on the copper core.

④ Iron core inductance: refers to the inductance of the coil wound on the iron core.

⑤ Inductance with tap: refers to the inductance with one or more taps drawn from the coil.

2. Inductance

Refers to the amount of inductance capacity, which is called inductance. The basic unit of inductance is Henry (H) for short, and the common units are milliohm (mH) and microohm（ μ H) Etc.

1H=103 mH=106 μ H

3. Inductive reactance (XL)

It refers to the blocking effect of inductance on AC (equivalent resistance). XL=2 л fL

4. Characteristics of inductance

It has the characteristics of DC resistance to AC and low frequency resistance to high frequency.

5. Self-induction of inductance

When the current passing through the inductive coil changes, the coil will produce a self-induced electromotive force to block the change of current. This effect is called self-induction of the inductor.

6. Mutual inductance

When two coils close to each other pass through a changing current, the other will also induce the induced electromotive force, which is called the mutual inductance of inductance. The transformer is made according to the principle of mutual inductance.

7. Purpose of inductor

It can be used for filtering, wave blocking, current limiting, transformation, tuning, vibration elimination and other functions.

8. Expression of inductance

① Directly indicate the value and unit of inductance. For example: 10mH, 150 μ H。

② The number of X stands for the number of X. For example, 1H2 is 1.2H, 3m3 is 3.3mH, 8 μ 2 i.e. 8.2 μ H。

③ Represented by color ring or color dot: represented by four-color ring (color dot), the first two-color ring (color dot) represents the effective number, the third color ring (color dot) represents the multiplier, and the fourth color ring represents the error. (Same as four-color ring resistance)

Grey red brown gold is 82X101 ± 5%

④ Expressed in turns

Some inductive coils do not indicate their inductance, but directly indicate the number of coils (turns) that should be wound by the inductive coil, such as 3T=3 turns (turns), 19T=19 turns, etc.

⑤ Many inductance coils are made by the manufacturer. There is neither inductance nor the number of coils. In practical applications, only the same coil can be replaced or rewound according to the original specification.

9. Judgment of inductance (coil)

The resistance range of the multimeter can be used to roughly test the quality of the inductive coil. The method is to compare the DC resistance at both ends of the coil with the normal value or the same coil. If the resistance value is basically the same (error ≤ ± 10%), the coil can be considered as good. If the resistance value difference is too large, the coil is bad. If the resistance value becomes infinite, the coil is open circuit damaged. If the resistance value becomes zero, the coil is short circuit damaged.

10. Fault and maintenance of inductance coil

① In case of short circuit or local short circuit fault of the inductive coil, the coil shall be disassembled and rewound according to the original specification to repair.

② In case of internal poor contact or open circuit fault of the inductive coil, the coil can be carefully disassembled for inspection. The poor contact (mostly at the coil joint) or open circuit can be repaired by re-welding firmly, or by re-winding with new wire according to the original specification.

③ In most cases, if there is a fault in the inductance coil, it is recommended to replace it if there is a new spare part, and repair it only if there is no new spare part.

4、 Transformer

Transformer is a multi-coil device that can transform AC voltage, current and impedance.

1. Relationship between AC voltage, current and impedance of transformer transformation:

N1 and N2 are the number of turns of the first stage; U1 and U2 are the voltage of the primary stage; I1 and I2 are the initial current respectively; Z1 and Z2 are the impedances of the primary stage. Primary coil (N1) is also called original coil; The secondary coil (N2) is also called the secondary coil.

The ratio of the number of turns of the primary stage of the transformer is proportional to the voltage of the primary stage, inversely proportional to the current of the primary stage, and directly proportional to the square root of the impedance of the primary stage. Expressed by formula:

2. Type of transformer

① High-frequency transformer: refers to the transformer used to transform high-frequency electrical signals. Such as antenna coil, oscillation transformer, etc.

② Intermediate frequency transformer: (commonly known as medium frequency transformer): refers to the transformer used to transform the medium frequency signal in the superheterodyne radio receiver.

③ Low-frequency transformer: refers to the transformer used to transform low-frequency electrical signals, such as audio transformer.

④ Power transformer: refers to the transformer used to convert AC mains power.

⑤ Autotransformer: refers to the transformer that can be shared by primary and secondary coils.

3. Judgment of transformer

The quality of the transformer can be roughly judged by using the resistance range of the multimeter. The method is to measure the DC resistance of each coil of the transformer and compare it with the normal value or a good transformer. If the resistance value of all coils is normal, the transformer can be considered as good; If one or more coils are defective or damaged. At the same time, it is normal to test the insulation resistance between different coils or between each coil and the shell (iron core) to be infinite, otherwise the transformer is also defective or damaged.

4. Fault and maintenance of transformer

① For the transformer with temperature fuse connected in series with the primary coil of the transformer, if the primary open circuit occurs, it is mostly caused by the temperature fuse fusing, which can be solved by replacing a temperature fuse. If there is no replacement of this fuse, it can also be solved by short-circuiting this fuse.

② For general transformers, if the coil is damaged, it can be repaired by rewinding according to the parameters of the original coil.

③ In most cases, it is recommended to replace the damaged transformer when it is difficult to repair or the repair project is too large.

5. Parameters and calculation of transformer

① Core sectional area (S): S=tongue width × Stacking thickness

② Relationship between core sectional area (S) and transformer power (P): S=1.25

③ Number of coils per volt (N): refers to the number of coils (turns) that should be wound per volt

F is the AC frequency, S is the cross-sectional area of the iron core, and Bmax is the magnetic induction intensity

④ Primary turns (N1) and secondary turns (N2)

N1=U1N (U1 is primary voltage); N2=U2N (U2 is the secondary voltage)

⑤ Wire diameter (d): refers to the wire diameter of the winding coil (mm).

I is the current of the wire (I=P/U)

Primary wire diameter d1=; Secondary wire diameter

5、 Semiconductor (crystal) diode (D)

Short for diode, it is a double-layer semiconductor device, composed of a PN junction, with the characteristics of unidirectional conduction.

1. PN junction

① P-type semiconductor: refers to the impurity semiconductor whose holes are mostly carriers.

② N-type semiconductor: refers to the impurity semiconductor with most carriers.

③ PN junction: The space formed at the interface of P-type semiconductor and N-type semiconductor is called PN junction.

④ Characteristics of PN junction: It has unidirectional conductivity.

2. Main electrical parameters of diode

① Forward current: refers to the electric current that is allowed to pass when the guide is turned on.

② Reverse breakdown voltage: refers to the electrical high voltage when the PN junction is reverse breakdown, that is, the withstand voltage of the diode.

③ Forward conduction voltage: refers to the voltage required for the forward conduction. Germanium material (PN junction): 0.2V (0.2-0.3V); Silicon material (PN junction): 0.6V (0.5-0.7V); The compound material is about 2V (1-3V).

④ Junction capacitance: refers to the capacitance formed by PN junction, which is called junction capacitance.

3. Purpose of diode

It can be used for rectification, voltage stabilization, switching, damping, tuning and other purposes.

4. Diode polarity judgment

① For general diodes, one end with a mark (such as color circle) is negative and the other end is positive.

② For LED, if the pin is not cut, the long pin is positive and the short pin is negative.

③ For diodes, the positive and negative poles can be seen directly from their internal structure.

④ Use the resistance range of the multimeter to judge: when testing the forward and reverse resistance of the diode with the resistance range of the multimeter, judge according to the characteristics of small forward resistance and large reverse resistance of the PN junction of the diode. During the test, the black lead with low resistance is connected to the positive pole, while the red lead is connected to the negative pole.

5. Judgment of diode (PN junction)

When testing the forward and reverse resistance of the diode with the resistance range of the multimeter, the smaller the forward resistance of the diode (PN junction) is, the better the reverse resistance is. If the forward and reverse resistance of the diode are very small or large, the tube has been broken down, short circuit or open circuit damage.

6、 Semiconductor triode

The triode is a three-layer semiconductor device that can amplify and switch signals. It is composed of two PN junctions.

1. Structure of triode

The triode is divided into PNP type and NPN type structures.

E or e represents emitter, B or b represents base, C or c represents collector, BC junction (bc junction): collector junction

BE junction (be junction): emission junction

2. Main electrical parameters of triode

① PCM: refers to the maximum dissipation power of the collector, that is, the maximum power of the triode. PCM<1W is small power tube; PCM>1W is high-power tube; The PCM=1W or so is medium power tube.

② ICM: refers to the maximum current of the collector, that is, the maximum current of the triode.

③ Bvceo: refers to the maximum reverse breakdown voltage between the collector and the emitter when the base is open, which is the withstand voltage of the triode.

④ Iceo: refers to the maximum reverse leakage current between the collector and emitter when the base is open, that is, the penetration current of the triode.

⑤ FT: refers to the characteristic frequency, that is, the frequency when the amplification factor in its emitter amplifier circuit drops to 1.

FT ≤ 3MHz is low frequency tube; FT>3MHz refers to high frequency tube; FT>hundreds of MHz is called UHF tube

⑥ HFE: DC amplification factor of triode (DC amplification factor)

HFE=(Ic is collector current, IB is base current)

⑦ β Value: refers to the AC magnification of the triode

( Δ IC is the change of collector current, Δ IB is the change of base current)

3. Differentiation between PNP type and NPN type

When measuring the positive and negative resistance between the pins of the triode with the resistance range of the multimeter, if the resistance of the red probe connected to one electrode and the black probe connected to the other two electrodes is relatively small, then this tube is PNP tube (P tube for short), and the electrode connected to the red probe is the base electrode; If the black probe is connected to a fixed electrode at one time and the red probe is connected to the other two electrodes, the resistance is relatively small, then this tube is NPN tube (referred to as N tube) and the black probe is connected to the base electrode.

4. Differentiation of three electrodes of triode

After the PNP and NPN tubes are determined according to the above method and the base electrode is found, the remaining two electrodes can be determined by the following method: the multimeter is set at RX1K of the resistance range, and the red and black probes are connected to the remaining two electrodes respectively. If the PNP tube is used, a resistance of about 100K is connected between the electrode and the base electrode of the red probe (this resistance can be replaced by fingers). If there is a significant change in the needle, the electrode of the red probe is the collector, The electrode connected to the black pen is the emitter; If this tube is NPN type tube, the polarity of the probe is just opposite, and the test method is the same as PNP type tube.

5. Amplification principle of triode

If the base current has a small change, the collector current will have a large change, that is, use a small current to control the large current to achieve current amplification, which is the amplification principle of the triode.

6. Judge the quality of triode

The smaller the forward resistance of the two PN junctions (emitter junction and collector junction, i.e. be junction and bc junction) of the triode tested with the resistance range of the multimeter (about a few K Ω when measured with the Rx1K range), the better, while the larger the reverse resistance (more than a few K Ω when measured with the Rx1K range, and most of the tubes are infinite), the better, If the forward resistance of two or one of the PN junctions is too large (for example, the Rx1K test has more than dozens of Ohms) or the reverse resistance is too small (for example, the Rx1K test is less than dozens of Ohms), the tube performance is poor. If the forward and reverse resistance of two or one of the PN junctions are very small (for example, basically zero) or both are large (for example, basically infinite), the tube is damaged due to two or one PN junction breakdown or open circuit. At the same time, the greater the positive and negative resistance between the collector and the emission analyzer (preferably infinite, but some tubes are more than tens of K Ω), the better the trap. If the resistance of the tube is too small, the penetration current of the tube is too large and the performance is poor. If the resistance is basically zero, the tube has been broken down between the collector and the generator, and the amplification capacity (HFE value) of the triode can also be measured with the HFE gear or estimated with the resistance gear. The amplification capacity is also different for different types and purposes of the tube, but it should have amplification capacity (the HFE value should be more than several times, and the tube without amplification capacity cannot be used.)

7. Fault and maintenance of triode

① In case of poor performance or damage of the triode, the triode cannot be repaired and can only be replaced with a new or good triode.

② When the triode is damaged, replace it with the same type of tube as far as possible. If there are no pipes of the same type, pipes with the same or similar performance parameters shall be selected.

③ When selecting the substitute pipe, its parameters Icm, Pcm, Bvceo and other parameters should be equal to or greater than the original type of pipe.

④ Low-frequency tubes can only be used in low-frequency circuits, while high-frequency tubes can be used not only in high-frequency circuits but also in low-frequency circuits. Therefore, in practical application, high frequency tube can replace low frequency tube, and vice versa.

7、 Nomenclature of semiconductor devices

1. China

It consists of numbers --- letters --- letters --- numbers --- (letters)

① The first number represents the number of electrodes, such as 2 - diode, 3 - triode

② The second letter indicates the material and polarity, such as: A - germanium material PNP type B - germanium material NPN type

C - silicon material PNP type D - silicon material NPN type E - compound material

③ The third letter indicates the type of device, such as:

G - high frequency low power tube A - high frequency high power tube

X - low frequency low power tube D - low frequency high power tube

K -- switch tube W -- voltage stabilizing tube P -- common tube E -- rectifier tube N -- damping tube B -- varactor tube

④ The fourth number indicates the registration number

⑤ The fifth letter uses letters A, B, C, D, etc. to indicate the improved version of the prototype

For example: 2AP9 -- germanium ordinary diode 2CW56 -- silicon zener diode 3DG6B -- silicon NPN type high frequency low power transistor is an improved type 3AX31 of 3DG6 -- germanium PNP type low frequency low power transistor 3BX31 -- germanium NPN type low frequency low power transistor 3CD511 -- silicon PNP type low frequency high power transistor 3DD15 -- silicon NPN type low frequency high power transistor

2. Japan

It consists of numbers - letters - letters - numbers - (letters)

① The first number is expressed as: 0 -- phototransistor; 1 - Diode and rectifier; 2 - triode and controllable rectifier.

② The second letter "S" refers to semiconductor devices.

③ The third letter indicates the type of device. The first item is 0, and the third item is not available for 1.

A - pnp high frequency B - PNP low frequency C - NPN high frequency D - NPN low frequency

J-P channel FET K-N channel FET

④ The fourth number indicates the registration number.

⑤ The fifth letter is used to distinguish the prototype from the variant. The letters A, B, C, D, etc. are used to indicate the improved version of the prototype.

For example, 2SC1815, 2SA1015, 2SC1942, 2SD3298A, 2SD1555, 2SK134, etc. Note: For the convenience of marking, the "2S" in front of the Japanese model triode is often omitted, such as A1015, C1815, C3298A, D1555, etc.

3. Europe

It consists of letters - letters - numbers - (letters).

① The first letter indicates the type of device used.

A -- germanium material B -- silicon material

② The second letter indicates the type of device.

A -- detector, switch, mixer triode; B -- varactor diode; C - low frequency low power tube; F - high frequency small power tube; D - low frequency low power tube; L - high-frequency high-power tube; S - low power switch tube; U - high-power switch tube; E - voltage stabilizing tube; Y -- Rectifier tube.

③ The third number represents the registration number.

One letter and two digits are used for special devices to indicate the registration number; The three-digit number of the universal device indicates the registration number.

④ The fourth letter, through the letters A, B, C, D, etc., indicates the improved version of the prototype or the mark of grading by a certain number.

For example, BF198 is a general-purpose device, silicon NPN type high-frequency low-power transistor; BUY71 is a special device, silicon NPN high-power switching triode.

4. United States

It consists of numbers - letters - numbers - (letters).

① The first number and the second letter "N" are expressed as: 1N - diode and rectifier; 2N -- triode and controllable rectifier; 3N -- quadrupole.

② The third number represents the registration number.

③ The fourth letter, A, B, C, D, etc., represents the improved version of the prototype. For example, 1N4007, 2N3055, etc.

5. Digital triode of Samsung, such as 9011901290139014901590169018.

8、 Integrated Circuit (IC)

Integrated circuit is a kind of micro electronic device or component. The transistor, diode, resistor, capacitor, inductor and other components needed in a circuit and wiring are interconnected by a certain process to be made on a small or several small semiconductor chips or dielectric substrates, and then packaged in a shell to become a micro-structure with the required circuit functions; All the components have formed a whole in structure, so the volume of the whole circuit has been greatly reduced, and the number of lead-out wires and welding points has also been greatly reduced, thus making the electronic components a big step towards miniaturization, low power consumption and high reliability.

The integrated circuit has the advantages of small size, light weight, less lead wires and welding points, long service life, high reliability, good performance, and low cost, which is convenient for large-scale production. It is not only widely used in industrial and civil electronic equipment such as radio recorder, television, computer, etc., but also widely used in military, communication, remote control, etc. Using integrated circuits to assemble electronic equipment, its assembly density can be tens to thousands of times higher than that of transistors, and the stable working time of the equipment can also be greatly improved.

It is represented in the circuit by the letter "IC" (also the letter symbol "N", etc.).

1. Classification of integrated circuits

（1） Classification by functional structure

According to their functions and structures, integrated circuits can be divided into analog integrated circuits, digital integrated circuits and digital/analog hybrid integrated circuits.

Analog integrated circuits, also known as linear circuits, are used to generate, amplify and process various analog signals (signals whose amplitude changes with time, such as audio signals of semiconductor radios, tape signals of video recorders, etc.). Their input signals are proportional to their output signals. Digital integrated circuits are used to generate, amplify and process various digital signals (signals with discrete values in time and amplitude, such as VCD, DVD playback audio signals and video signals).

（2） Classification by manufacturing process

According to the manufacturing process, integrated circuits can be divided into semiconductor integrated circuits and thin film integrated circuits.

Film integrated circuits are classified into thick film integrated circuits and thin film integrated circuits.

（3） Classification by integration level

According to the degree of integration, integrated circuits can be divided into small-scale integrated circuits, medium-scale integrated circuits, large-scale integrated circuits, ultra-large-scale integrated circuits, ultra-large-scale integrated circuits and large-scale integrated circuits.

（4） Classified by conductive type

According to the conductive type, integrated circuits can be divided into bipolar integrated circuits and unipolar integrated circuits, both of which are digital integrated circuits

The manufacturing process of bipolar integrated circuits is complex and the power consumption is large. The representative integrated circuits include TTL, ECL, HTL, LST-TL, STTL and other types. The manufacturing process of unipolar integrated circuits is simple, and the power consumption is low. It is easy to make large-scale integrated circuits. The representative integrated circuits include CMOS, NMOS, PMOS and other types.

（5） Classification by use

According to the purpose, integrated circuits can be divided into integrated circuits for television, audio, video player, video recorder, computer (microcomputer), electronic organ, communication, camera, remote control, language, alarm and various special integrated circuits.

（6） By application field

Integrated circuits can be divided into standard general integrated circuits and special integrated circuits according to application fields.

（7） By shape

According to the shape, integrated circuits can be divided into round (metal case transistor packaging type, generally suitable for high power), flat (good stability, small size) and dual in-line type

2. Package type of integrated circuit

① In-line package

In-line packaging integrated circuit is a kind of integrated circuit packaging form in which the pins are inserted into the printed board and then welded. It mainly includes single-line packaging and dual-line packaging. Single-inline package includes Single-inline package (SIP for short) and Zig-ZagInlinePackage (ZIP for short). The integrated circuit of single in-line package has only one row of pins, and the integrated circuit of single in-line package is installed in two rows. The dual-inline package, also known as DIP package, has two rows of pins. Suitable for perforation installation of PCB; Easy to wiring PCB; Easy installation. The structural forms of DIP mainly include multilayer ceramic DIP package, single-layer ceramic DIP package, lead frame package, etc.

② . Chip packaging

With the improvement of production technology, the volume of electronic products is becoming smaller and smaller, and the larger size of in-line packaged integrated circuits can no longer meet the needs. Therefore, the designer has developed a kind of integrated circuit with SMD package. The integrated circuit pin of this package is very small and can be directly welded on the printed wire of the printed circuit board. The integrated circuits of SMT package mainly include thin QFP (TQFP), thin pin pitch QFP (VQFP), narrow QFP (SQFP), plastic QFP (PQFP), metal QFP (MetalQFP), tape QFP (TapeQFP), J-pin small form factor package (SOJ), thin small form factor package (TSOP), very small form factor package (VSOP), narrow S OP (SSOP), thin narrow SOP (TSSOP) and small form factor integrated circuit (SOIC) and other derivative packages.

③ . BGA package (Ball Grid ArrayPackage)

Also known as ball grid array package, the BGA package pins are distributed under the package in the form of round or columnar solder joints. The integrated circuits adopting this packaging form mainly include CPU and high density, high performance and multi-function integrated circuits such as North-South Bridge.

The advantage of BGA packaging integrated circuit is that although the number of pins increases, the pin spacing does not decrease but increases, thus improving the assembly yield; The thickness and weight are reduced compared with the previous packaging technology; The parasitic parameters are reduced, the signal transmission delay is small, and the use frequency is greatly increased; The assembly can be coplanar welded with high reliability.

④ . Thick film packaging thick film

The integrated circuit is a kind of modular integrated circuit that integrates the special integrated circuit chip and the relevant capacitance and resistance components on a substrate, and then uses the standard packaging form outside, and leads out the pins.

3. Judgment of integrated circuit

① Measuring internal resistance method

Use the R of the resistance range of the multimeter × Measure the forward and reverse resistance of each pin to ground or between each pin in gear 1K when the IC is not in the circuit, and compare it with the normal value or good IC. If the resistance value is basically the same (error ≤ ± 10%), the IC can be considered as good; If the resistance values of some or all pins differ too much, the IC is defective or damaged.

② Measuring in-circuit resistance method

Use the R of the resistance range of the multimeter × Measure the positive and negative resistance values of each pin of the IC to the ground (refer to the ground wire of the circuit board) on the circuit board at 1K gear and compare them with the normal value or a good circuit board. If the resistance values are basically the same (error ≤ ± 10%), the IC can be considered as good; If the resistance values of some or all pins differ too much, the IC is defective or damaged if the peripheral circuit components of some or all pins are normal.

③ Measuring DC working voltage method

Use the DC voltage range of the multimeter to measure the DC working voltage of each pin of the IC to the ground and compare it with the normal value or a good circuit. If the voltage value is basically the same (error ≤ ± 10%), the IC can be considered as good; If the voltage value error is too large, the IC is bad or damaged when the peripheral circuit components of the corresponding pins are normal.

④ Substitution method

If the IC cannot work normally when the peripheral components of the IC are checked to be normal, a good IC can be used to replace the IC that is suspected to be damaged. If the circuit can work normally after replacement, it indicates that the original IC is defective or damaged; If the circuit still does not work properly after replacement, the original IC may not be damaged, so continue to check the peripheral circuit components.

9、 Speaker

Commonly known as loudspeaker, it is an electro-acoustic converter device that can convert audio electrical signals into sound.

1. Type of loudspeaker

① Piezoelectric ceramic horn: It is composed of piezoelectric ceramic chips and is made according to the principle of piezoelectric effect.

② Electric horn: composed of permanent magnet, voice coil, paper tray, diaphragm, etc. The sound generation principle is: according to the principle that the same magnetic poles repel each other and the opposite magnetic poles attract each other, when the voice coil is connected with the audio electric signal, the audio electromagnetic field will be generated and the magnetic field generated on the permanent magnet will generate the interaction force, so the voice coil drives the paper tray to move, so that the paper tray vibrates the air to produce sound.

2. Main electrical parameters of loudspeaker

① Power: divided into minimum power and maximum power

Minimum power (PMIN): also called undistorted power, refers to the power with distortion within the rated range.

Maximum power (PMAX): also called peak power, refers to the maximum power that the horn can withstand.

② Impedance: refers to the equivalent resistance of the speaker to the audio electrical signal. Impedance=DC resistance of voice coil+voice coil inductance.

③ Frequency characteristics: refers to the frequency range of the sound replayed by the speaker, including full-range treble, mid-range, bass, etc. The frequency range of sound is 20Hz - 20KHz.

④ Caliber: refers to the diameter of the speaker tray.

3. Judgment of horn quality

Use the 1 Ω gear of the resistance gear of the multimeter to roughly judge the quality of the horn. The method is as follows: the DC resistance of the voice coil should be slightly less than the impedance value of the speaker, and the speaker should be able to make a "click" sound during the test, which is normal. If the DC resistance is too small, the voice coil will be damaged by short circuit. If the resistance value is infinite, the voice coil will be damaged by open circuit. At the same time, press the paper tray gently with your hand, which should be elastic and free of noise, otherwise the speaker will also be poor.

4. Phase judgment of loudspeaker

① It can be directly seen from the horn terminal that the plus sign (+) is the positive phase and the minus sign (-) is the negative phase.

③ Connect the red and black probes at the lowest range of the DC voltage (current) range of the multimeter (such as 0.5V range) to both ends of the horn terminal, and then press the paper tray gently with your hand. If the probe will swing slightly to the right, the polarity of the probe is just the opposite.

5. Loudspeaker failure and maintenance

① It is recommended to replace a new speaker of the same model in case of speaker failure, but it can also be repaired if there is no new speaker to replace or if you want to reduce the repair cost.

② Repair of broken voice coil outgoing line: When the speaker is used for a long time or the lead quality is too poor, the voice coil outgoing line is easily broken due to the vibration of the paper tray. At this time, the same or similar speaker special braided flexible wire can be replaced to repair. Note: Please do not replace it with other hard wires or fancy wires, otherwise not only the sound quality will be affected, but also the lead wire will be easily broken again.

③ If the voice coil is damaged, the dust cover and the old voice coil shall be soaked with Ω Ω Tiana water (banana water) and replaced with the same type of voice coil (also can be wound by itself). The replacement voice coil shall be fixed with adhesive according to the position of the original voice coil. If it is difficult to separate the original position, You can also install the voice coil wire first, and then connect the voice signal to adjust the position of the voice coil so that the maximum sound quality is the best, and then fix it with adhesive and dry it.

④ If the paper tray is damaged, it can be repaired by repairing the damaged part with the same paper tray material. If the paper tray is seriously damaged, it can only be replaced with a new paper tray.

⑤ If the iron core and permanent magnet are loose and displaced, resulting in collision with the voice coil, it is generally difficult to repair under amateur conditions, and it is recommended to replace a new speaker.

⑥ For the dome tweeter, because the voice coil and the paper tray (diaphragm) are an integral part, if the voice coil is damaged, disassemble the old voice coil assembly and replace it with a new voice coil spare assembly (its repair is the simplest).

11、 Crystal and filter

1. Crystal: also called crystal oscillator, crystal oscillator, resonator, etc. It is composed of quartz chips or piezoelectric ceramic chips and is often used in oscillation circuits.

2. Filter: crystal filter and ceramic filter are commonly used to select or filter the signal of a certain frequency.

3. Acoustic surface filter: composed of interdigital transducer

12、 Composite device

It refers to a device made or combined by multiple identical or different devices, which is called a composite device.

1. Resistance recombination

One end is connected together by multiple resistors with the same resistance value as the common end.

2. Capacitance recombination

Multiple single capacitors with the same capacity are used to connect one end of them together as a capacitor bank composed of the common end or packaged together in the same manufacturing process.

3. Inductance and capacitance combination

It refers to the connection of multiple inductance coils and capacitors in a certain way, which is mainly used for filters.

4. Half bridge pile

It is composed of two rectifier diodes packaged together, and is mostly used in rectifier circuits.

5. Full bridge reactor

For short, bridge is composed of four rectifier diodes connected together in a certain way. It is often used in rectifier circuits.

6. Transistor with voltage divider (with resistance)

Refers to a triode with a voltage divider between the base and emitter.

7. Transistor with damping diode and shunt resistor

8. Composite pipe (Darlington pipe)

It is composed of two triodes. The polarity of the composite tube is the same as that of the front tube. The magnification of the composite tube is the product of the magnification of the two tubes.

9. Photocoupler

A light-emitting diode and a photosensitive triode are packaged together to form a photoelectric coupler.

The common types are four-pin optocoupler and six-pin optocoupler