Class = "keylink" > > diode

"D" is commonly used in crystal diode in the circuit and digital representation, such as: D5 said Numbers for 5 diode.

1, role: the main characteristics of diode is a one-way electrical conductivity, which is under the action of forward voltage, conduction resistance is small; While under the effect of reverse voltage on resistance greatly or infinity. Because of diode with the above properties, cordless telephone, to use it on rectification, isolation, voltage regulator, polarity protection, coding modulation, frequency modulation and static noise control circuits. Telephone do you use in the crystal diode according to the function can be divided into: (e.g., 1 n4004), isolation diode rectifier diode (e.g., 1 n4148), schottky diode (such as BAT85), light-emitting diodes, zener diodes, etc.

2, recognition methods: identification of a diode is very simple, small power diode N pole (cathode), in the diode looks mostly adopts a circular color standard, some diodes also use special symbols to represent a P (positive) or N (cathode), also have use symbols for "P", "N" to determine of polarity of the diode. Across the electrodes of light-emitting diodes (leds) from the length of the pin to identify, long feet is positive, negative short feet.

3, test, note: when using a digital multimeter to measuring diode, red pens and pick up the positive, of the diode black pens and diode of the cathode, the measured resistance is the diode is the guide of value, the pointer multimeter pens and connection of the reverse.

4, commonly used 1 n4000 series diode voltage comparison is as follows:

Type 1 n4001 n4002 n4003 1 n4004 n4005 1 1 n4007 n4006

Withstand voltage (V) 50, 100, 200, 400, 600, 800, 1000-1 (A) current

Electronic components (4) < > zener diode

Zener diode "lh-zd" is commonly used in the circuit and digital representation, such as: ZD5 said Numbers for 5 regulator tube.

1, the zener diode voltage stabilizing principle: the characteristics of the zener diode is breakdown, the voltage at the ends of the basic remain unchanged. So, when the voltage regulator tube access circuit, if because of the power supply voltage fluctuations, or other causes circuit, the voltage changes at various points in the load on both ends of the voltage will be basic remain unchanged.

2, fault features: the zener diode failure in open circuit, short circuit and voltage values are not stable. Before this three kinds of fault, fault show a higher power supply voltage; After the two fault performance for low supply voltage change to zero volts or output instability. Types and voltage value of the zener diode is commonly used in the following table:

Type 1 n4728 n4729 1 n4730 n4732 1 n4733 n4734 1 n4735 n4744 1 n4750 n4751 1 n4761

Voltage of 3.3 V to 3.3 V, 3.9 V to 4.7 V, 5.1 V to 5.6 V, 6.2 V to 15 V 27 V 30 V to 75 V

Electronic components (5) < > inductor

"L" is commonly used in the circuit inductance with digital representation, such as: Numbers for 6 L6 said inductance. Inductance coil is insulated wires on the skeleton of the insulation around a certain number of turns. Dc can be through the coils, dc resistance is the resistance of the wire itself, the pressure drop is small; When ac signal through the coil, will produce self-induced electromotive force on both ends of the coil, self inductance electromotive force direction is opposite to the direction of the applied voltage, the way of communication, so the inductance dc resistance are the characteristics of communication, the higher the frequency, the greater the coil impedance. Inductance in the circuit and capacitance of the oscillation circuit. Inductance usually have a standard method and standard method of color, color standard method similar to resistance. Such as: brown, black, gold, gold said 1 uh inductance of error (5%). The basic unit of inductance is: heng (H) conversion unit has: 1 H = 103 mh = 106 uh

Electronic components (6) < varactor >

Varactor is according to the common internal "p-n junction diode junction capacitance can changes over plus reverse voltage this principle specially designed a special kind of diode. Varactor diodes in cordless telephone mainly used in mobile phone or fixed phone, high frequency modulation circuit to realize low frequency signal modulation to the high frequency signal, and launch out. In working status, varactor modulation voltage on the cathode commonly, make the interior of the varactor junction capacitance capacity changes over modulation voltage. Varactor fails, main show is the leakage or performance variation: (1) the leakage occurs, the high frequency modulation circuit will not work or modulation performance becomes poor. (2) varactor performance becomes poor, work is not stable, high frequency modulation circuit made of high frequency modulated signal is sent to the other side are produce distortion when received by the other party. One of the above situation, the same model of varactor diode should be replaced

Electronic components (7) < crystal triode >

Transistor "Q" is commonly used in the circuit with digital representation, such as: Q17 said Numbers for 17 triode.

1, characteristics: transistor (triode) is an internal contains two p-n junction, and special device capable of amplification. It divides the NPN and PNP two types, the two types of triode can compensate for each other from the job characteristics, the so-called OTL circuit of the pipe is used by PNP and NPN pairing. That is commonly used in telephone PNP transistors are: A92, 9015 model; NPN transistors are: A42, 9014, 9018, 9013, 9012 models.

2, transistor amplifying role is mainly used for amplification circuit, there are three kinds of connection in the common circuit. Three kinds of connection for comparison, the transistor circuit has the characteristics listed in the table below, for your reference. The name of the Common emitter circuit The common collector circuit (emitter follower) in common base circuit input impedance (hundreds of Europe to thousands of European) large (more than tens of thousands of European) small (several European ~ o) in the output impedance (thousands of oh ~ tens of thousand oh) small (several European ~ o) big (tens of thousands of Europe to hundreds of thousands of European) voltage magnification big is small (less than 1 and close to 1) large current magnification Big (tens) (tens) small (less than 1 and close to 1) power magnification Large (about 30 ~ 40 decibels) small (about 10 db) (about 15 ~ 20 db) frequency characteristic in high frequency difference good good table used multistage amplifier intermediate grade, low frequency amplifier input stage, output stage with high frequency or broadband impedance matching circuit and constant current source circuit

Electronic components (8) < > field effect transistor amplifier

1, field effect transistor has the advantages of high input impedance and low noise, and therefore is widely used in various kinds of electronic equipment. Especially useful effect tube to do the input stage of the electronic equipment, can get the general performance of the transistor is very difficult to achieve.

2, the field effect tube into two categories junction and insulated gate type, the control principle is the same. # 3, field effect tube with comparison (1) the field effect transistor is voltage control element, and the transistor is the current control components. The only allowed from the signal source under the condition of low current, should choose to use effect tube; In the low voltage signal, and allows more from the source current conditions, should choose transistor. (2) the field effect tube is the use of majority carrier conductive, so called the unipolar device, the transistor is the majority carrier, also make use of the minority carrier conductive. Is called "bipolar devices. (3) some of the field effect tube source and drain can be used interchangeably, grid voltage can also be positive or negative, flexibility is better than the transistor. (4) the field effect tube in the small current and low voltage under the conditions of work, and its manufacturing process can be easily put a lot of field effect tube integrated on a silicon wafer, so field effect tube has been widely in the large scale integrated circuit

Electronic components (9) microcontroller > < * 1

Microcontroller hardware system design principles (quote) zt (icbase.com), a single chip microcomputer application system hardware circuit design includes two parts: one is expanding system, namely the internal functions of the microcontroller unit, such as ROM, RAM, I/O, timer/counter, interrupt system can not meet the requirements of application system, must expand outside the piece, select the appropriate chips, the corresponding circuit design. Second, the system configuration, that is, according to the demand of system function of peripheral equipment, such as the keyboard, monitor, printer, A/D, D/A converters, etc., to design appropriate interface circuit. The expansion of the system and configuration should follow the following principles:

1, as far as possible choose typical circuit, and conform to the SCM regular usage. To lay a good foundation for the standardization and modularization of the hardware system.

2, system expansion and peripheral equipment configuration level should fully meet the functional requirements of the application system, and proper leeway for secondary development.

3, the structure of the hardware should be combined with the application software solutions taken together. The hardware structure and software solutions will produce influence each other, considering the principle is: the software can realize the function of the real stirred by software as far as possible, in order to simplify the hardware structure. But must pay attention to, by the software realization of hardware function, average response time is longer than the hardware implementation, and CPU time.

4, related devices in the system to do performance matching as much as possible. If choose CMOS chip microcontroller constitute a low power system, the system of all chip should as far as possible choose low power consumption products.

5, reliability and anti-interference design is an indispensable part of hardware design, it includes chip, component selection, its decoupling filtering, printed circuit board wiring, channel segregation, etc.

6, MCU peripheral circuit is large, must consider the ability to drive. Driving ability is insufficient, the system work is not reliable, by adding line drive enhance their ability to drive or to reduce the power consumption of the chip to reduce the bus load.

7, as far as possible in the direction of the "monolithic" hardware system design. System components, the more mutual interference between devices is also strong, increases power consumption, also inevitably reduce the stability of the system. As the MCU chip integration function is stronger and stronger, the real SoC has been achieved on A chip system, such as ST company's newly minted mu PSD32 x series of products in A chip used 80 c32 nuclear, large capacity FLASH memory, an SRAM, A/D, I/O, two serial ports, watchdog, power on reset circuit, etc. System hardware anti-jamming methods practice the main factors influencing the reliable safe operation of the single-chip microcomputer system mainly comes from all kinds of electrical system internal and external disturbance, and the system structure design, component selection, installation and manufacture process. All of these constitute a single-chip microcomputer system interference factors, disorder, often leads to system working light affect product quality and yield, weight can lead to accidents, causing great economic losses.

Form the interference has three basic elements: (1) interference sources. Refers to the interference of components, equipment or signal, using mathematical language, described as follows: du/dt and di/dt big place is interference sources. Such as lightning, relay, silicon controlled rectifier, motor, high frequency clock may be interference sources. (2) the propagation path. Refers to the interference from the interference source to the access of the sensitive device or medium. A typical interference of conduction of the path is through a wire transfer and space radiation. (3) the sensitive device. Refer to objects are easy to be interference. Such as: A/D, D/A converter, single chip microcomputer, digital IC, such as weak signal amplifier. The classification of the classification of the interference of category 1 interference interference has a good variety of, often can be in accordance with the causes of noise, the transmission way, waveform characteristics and so on different classification. According to the causes of points: can be divided into the discharge noise, high frequency oscillation, surge noise. According to the transmission way points: can be divided into common mode noise and noise series mode. According to the waveform points: can be divided into continuous sine wave, pulse voltage, pulse sequence, and so on. 2 interference methods of coupling interference sources of interference signal is through certain coupling channels to exert influence on the measurement and control system. Therefore, it is necessary to I see transfer mode between the interference sources and interfered with the object. Interference mode of coupling, no more than is through a wire, space, public line, and so on, segmentation, basically has the following kinds: (1) direct coupling: this is the most direct way, is also one of the most common way in the system. Such as the disturbance signal through the power cord into system. For this kind of form, the most effective way is to join decoupling circuit. Thus good inhibition (2) public impedance coupling: this is the common way of coupling, this form often happens in two circuit current path. In order to prevent this kind of coupling, usually consider on the circuit design. The interference sources and interfered with no public impedance between objects. (3) the capacitance coupling: also called to electric field coupling or electrostatic coupling. Is due to the existence of the distributed capacitance coupling. (4) electromagnetic induction coupling: also called magnetic field coupling. Is the result of the distribution of electromagnetic induction coupling. (5) leakage coupling: this is a pure resistive coupling, in bad insulation will happen. Commonly used hardware anti-jamming technology In view of the three elements of forming interference, the anti-interference basically has the following means. 1 suppress interference sources suppress interference sources is as far as possible reduce the interference sources of the du/dt and di/dt. This is a top priority in the design of anti-interference and the most important principle, often have twice the result with half the effort. Reduce the interference sources of the du/dt is mainly done by shunt capacitance interference sources at both ends. Reduce the interference sources of the di/dt is in the loop series inductance and resistance and increase the fly-wheel diode.

Form the interference has three basic elements: (1) interference sources. Refers to the interference of components, equipment or signal, using mathematical language, described as follows: du/dt and di/dt big place is interference sources. Such as lightning, relay, silicon controlled rectifier, motor, high frequency clock may be interference sources. (2) the propagation path. Refers to the interference from the interference source to the access of the sensitive device or medium. A typical interference of conduction of the path is through a wire transfer and space radiation. (3) the sensitive device. Refer to objects are easy to be interference. Such as: A/D, D/A converter, single chip microcomputer, digital IC, such as weak signal amplifier. The classification of the classification of the interference of category 1 interference interference has a good variety of, often can be in accordance with the causes of noise, the transmission way, waveform characteristics and so on different classification. According to the causes of points: can be divided into the discharge noise, high frequency oscillation, surge noise. According to the transmission way points: can be divided into common mode noise and noise series mode. According to the waveform points: can be divided into continuous sine wave, pulse voltage, pulse sequence, and so on. 2 interference methods of coupling interference sources of interference signal is through certain coupling channels to exert influence on the measurement and control system. Therefore, it is necessary to I see transfer mode between the interference sources and interfered with the object. Interference mode of coupling, no more than is through a wire, space, public line, and so on, segmentation, basically has the following kinds: (1) direct coupling: this is the most direct way, is also one of the most common way in the system. Such as the disturbance signal through the power cord into system. For this kind of form, the most effective way is to join decoupling circuit. Thus a good inhibition. (2) public impedance coupling, it is also a common way of coupling, this form often happens in two circuit current path. In order to prevent this kind of coupling, usually consider on the circuit design. The interference sources and interfered with no public impedance between objects. (3) the capacitance coupling: also called to electric field coupling or electrostatic coupling. Is due to the existence of the distributed capacitance coupling. (4) electromagnetic induction coupling: also called magnetic field coupling. Is the result of the distribution of electromagnetic induction coupling. (5) leakage coupling: this is a pure resistive coupling, in bad insulation will happen. Commonly used hardware anti-jamming technology In view of the three elements of forming interference, the anti-interference basically has the following means. 1 suppress interference sources suppress interference sources is as far as possible reduce the interference sources of the du/dt and di/dt. This is a top priority in the design of anti-interference and the most important principle, often have twice the result with half the effort. Reduce the interference sources of the du/dt is mainly done by shunt capacitance interference sources at both ends. Reduce the interference sources of the di/dt is in the loop series inductance and resistance and increase the fly-wheel diode.

Selection of electronic components (10) < transistor experience >

Transistor variety, different with different electronic circuits of electronic equipment, various performance indexes of the transistor requirements are different. So, should according to the specific requirements of the application circuit to choose different USES, different types of transistors.

1. The general selection of high frequency transistor general small signal processing put (such as images, audio, buffer amplifier, etc.) used in the circuit of high frequency transistor, can choose characteristic frequency range in 30 ~ 300 MHZ high-frequency transistor, such as 3 dg6, 3 sa673 sa1015 cg21 dg8 and 3 and 2 and 2, 2 sa733, S9011, S9012, S9014 and S9015, 2 n5551, 2 n5401, BC337, BC338, BC548, BC558 models of small power transistor, can choose according to the requirement of the circuit material and polarity transistor, consider the dissipation power of chosen transistor, the collector maximum current, maximum reverse voltage, current amplification coefficient and nonlocal humanoid size parameters, such as whether meet the requirements of the application circuit.

2. The final visual put at the end of the selection of output tube used in color TV set level depending on the output pipe, should choose high frequency transistor characteristic frequency is higher than 80 MHZ. 21 (= 0.0254 m) in the following in small and medium-sized screen color TV is used in the final stage of visual output tube, the dissipation power should be greater than or equal to 750 mw, the largest collector current should be greater than or equal to 50 ma, reverse voltage should be greater than 200 v, generally can choose 3 dg182j, 2 sc3942 sc2229 and 2 types of transistors, etc. 25 inches above the large screen color TV set used in the final stage depending on the delivery pipe, the dissipation power should be greater than or equal to 1.5 W, the largest collector current should be greater than or equal to 50 ma, reverse voltage should be greater than 300 v, generally can choose 3 dg182n, 2 sc2611 sc2068 and 2, 2 sc2482 type of transistor.

Line 3. Promote the selection of pipe line drive pipe used in color TV, and high-power high-frequency transistor should be chosen. The dissipation power should be greater than or equal to 10 w, the largest collector current should be more than 150 ma, reverse voltage should be greater than or equal to 250 v. Generally can choose 3 dk204, sc2482 sc1569 and 2, 2 sc2655, 2 sc2688 models of triode, etc.

Line 4. Output pipe lines used in the selection of color TV tube belongs to high back pressure power transistor, the highest reverse voltage should be greater than or equal to 1200 v, the dissipation power should be greater than or equal to 50 w, the largest collector current should be greater than or equal to 3.5 A (dissipation power of the large screen color TV line output pipe should be greater than or equal to 60 w, the largest collector current should be greater than 5 A). 21 inches below the small screen color TV tube line output can choose 2 sd869, 2 sd870 sd950, 2 sd899a sd871, 2, 2