Section 1 resistor

Resistance, usually abbreviated as R, is a basic property of a conductor, which is related to its size, material and temperature. Ohm's law says that I=U/R, then R=U/I, and the basic unit of resistance is ohm, which is expressed by the Greek letter "ω". There is a definition: applying a voltage to a conductor produces a resistance corresponding to an ampere current. The main function of the resistor is to prevent the current from flowing. In fact, "resistance" refers to a property, and the resistance usually referred to in electronic products refers to elements such as resistance. The master said to his apprentice, "Find a resistance of 100 ohm!" , refers to the resistance whose "resistance value" is 100 ohm, usually referred to as ohm for short. The units commonly used to express the resistance of resistors are kiloohms (kω) and megaohms (mω).

I. Types of resistors

There are many kinds of resistors, which are usually divided into fixed resistors, variable resistors and special resistors. In electronic products, fixed resistors are the most widely used. Fixed resistors can be divided into many categories according to their manufacturing materials, but RT-type carbon film resistors, RJ-type metal film resistors, RX-type wire-wound resistors and chip resistors widely used in recent years are commonly used. The model name is very regular, R stands for resistance, T carbon film, J metal and X-ray winding, which is the first letter of Pinyin. In the old electronic products made in China, it is often seen that the resistor coated with green paint is RT-type. The red resistor is RJ type. Most of the old electronic products are green resistors. Why? This involves the problem of product cost, because the metal film resistor has high precision and good temperature characteristics, but the manufacturing cost is also high, while the carbon film resistor is particularly cheap, which can meet the requirements of civil products.

Of course, resistors also have power. The common one is 1/8 watt "color ring carbon film resistor", which is most used in electronic products and electronic production. Of course, in some micro-products, the resistance of116W will be used, which is much smaller. Then there is the microchip resistor, which is a member of the patch component family. It used to be more common in imported micro-products, but now electronic enthusiasts can buy it (as a wireless bug? )

Second, the identification of resistors

These directly marked resistors are easy to identify when they are newly bought. However, when assembling electronic products, we must consider the convenience of future maintenance and face the marking face to the place where it is easy to see. So pay special attention when bending your feet. If it is assembled by hand, it is not a big problem to add this process, but the machines on the automatic production line are not so intelligent. Moreover, the resistance element becomes smaller and smaller, and the directly marked mark is difficult to see. Therefore, the "color ring labeling method" is widely used in the world. In fact, "color ring resistance" occupies the mainstream position of resistance elements. As the name implies, "color ring resistance" is to use rings of different colors to represent the specifications of resistance. Some are represented by four color rings, while others are represented by five. What's the difference? Yes, four-ring resistance, usually carbon film resistance, is represented by three-color ring, and the error is represented by 1 color ring. Five-ring resistor is generally a metal film resistor. In order to better represent the accuracy, four color rings are used to represent the resistance value, and the other color ring is also used to represent the error.

The rule of color ring resistance is that the last circle represents the error. For a four-ring resistor, the first two rings represent the effective value and the third ring represents the multiplied power. Don't be afraid, I only remember the colors and numbers, but I don't remember the rest. There is a secret: face a color ring resistor, find the gold or silver end, turn it down and read the color ring from the beginning. For example, if the first ring is brown, the second ring is black, the third ring is red and the fourth ring is gold, then its resistance value is 1, 0, and the third ring is the number of zeros added. Two zeros are added to this resistor, so its actual resistance value is1000Ω, which is1kΩ.

Third, variable resistance.

Variable resistor is also called potentiometer, and the volume potentiometer on electronic equipment is variable resistor. However, it is generally believed that the potentiometer can be adjusted manually, while the variable resistance is generally small, so it is not often adjusted when installed on the circuit board. A variable resistor has three pins, and the resistance value between the two pins is fixed. This resistance value is called the resistance value of the variable resistor. The resistance between the third pin and any two pins can change with the rotation of the shaft arm. In this way, the voltage or current in the circuit can be adjusted to achieve the effect of adjustment.

Fourth, special resistance.

Photosensitive resistor is an element whose resistance changes with the intensity (brightness) of external light. The stronger the light, the smaller the resistance value, and the weaker the light, the greater the resistance value. Its outline and circuit symbols are shown in Figure 2. If the two pins of the photoresistor are connected to the probe of the multimeter, the resistance of the photoresistor under different illumination will be measured with the R× 1k range of the multimeter: the reading of the multimeter will change when the photoresistor is moved from a dark drawer to sunlight or light. In the case of complete darkness, the resistance of the photosensitive resistor can reach more than several megaohms (the multimeter indicates that the resistance is infinite, that is, the pointer does not move), while under strong light, the resistance can be reduced to several thousand ohms or even below 1 kiloohms.

Using this characteristic, we can make all kinds of light-controlled small circuits. In fact, most street lamps are automatically controlled by light-controlled switches, and one of the important components is photoresistor (or phototransistor, a semiconductor component with similar function and amplification). Photosensitive resistor is made by depositing a layer of cadmium sulfide (CdS) film on ceramic substrate, which is actually a semiconductor element. The acoustic corridor lights in Xincun will not light up during the day, also because the photoresistors are working. We can use it to make electronic crow chickens, which crow at dawn in the morning.

Thermistor is a special semiconductor device, and its resistance changes with the surface temperature. It was originally used to make electronic equipment work normally at different ambient temperatures, and it is called temperature compensation. The new computer motherboards have CPU temperature measurement and over-temperature alarm functions, that is, thermistors are used.

Section 2 capacitor

Various capacitors are needed in electronic manufacturing, which play different roles in the circuit. Similar to a resistor, it is usually referred to as a capacitor for short, and is represented by the letter C. As the name implies, a capacitor is a "container for storing charge". Although there are many kinds of capacitors, their basic structures and principles are the same. A capacitor consists of two closely spaced metal sheets separated by a substance (solid, gas or liquid). Two pieces of metal are called boards, and the substance in the middle is called medium. Capacitors are also divided into fixed capacity and variable capacity. But the common ones are constant capacity capacitors, and the most common ones are electrolytic capacitors and ceramic capacitors.

Different capacitors have different abilities to store charge. It is stipulated that the amount of charge stored when a DC voltage of 1 volt is applied to the capacitor is called the capacitance of the capacitor. The basic unit of capacitance is farad (f). But in fact, farad is a very unusual unit, because the capacity of capacitor is often much smaller than 1 farad. Commonly used methods are micron method (μF), nano method (nF) and micro method (micro method is also called micro method), and their relationship is: 1 farad (f) = 100000.

In electronic circuits, capacitors are used to block direct current through alternating current, and also serve as filters to store and release charges, so as to smoothly output pulsating signals. Capacitors with small capacity are usually used in high-frequency circuits, such as radios, transmitters and oscillators. Large-capacity capacitors are usually used to filter and store charges. Moreover, there is another feature. Generally, capacitors above 1μF are electrolytic capacitors, and capacitors below 1μF are mostly ceramic capacitors. Of course, there are others, such as monolithic capacitors, polyester capacitors and small-capacity mica capacitors. The electrolytic capacitor has an aluminum shell, which is filled with electrolyte, and two electrodes are led out as a positive electrode (+) and a negative electrode (-). Unlike other capacitors, their polarity in the circuit cannot be wrong, while other capacitors have no polarity.

Connect the two electrodes of the capacitor to the positive electrode and the negative electrode of the power supply respectively. After a period of time, even if the power supply is turned off, there will still be residual voltage between the two pins (you can observe it with a multimeter after learning the tutorial). We say that a capacitor stores charge. When a voltage is generated between the plates of a capacitor, electric energy is accumulated. This process is called capacitor charging. There is a certain voltage across the charged capacitor. The process that the charge stored in the capacitor is released into the circuit is called the discharge of the capacitor.

For example, in real life, we can see that after unplugging the plug, the LED on the commercial rectifier power supply will continue to light for a while, and then gradually go out, because the capacitor inside stores the electric energy in advance and then releases it. Of course, this capacitor was originally used for filtering. As for capacitive filtering, I don't know if you have heard of the Walkman with rectifier power supply. Generally, low-quality power supply buzzes in headphones because manufacturers use small-capacity filter capacitors in order to save costs. At this time, a large-capacity electrolytic capacitor (1000μF, note that the positive electrode is connected to the positive electrode) can be connected in parallel at both ends of the power supply, which can generally improve the effect. Enthusiasts should at least use 1000 microfabrication to filter when making HiFi audio. The larger the filter capacitor is, the closer the output voltage waveform is to DC. The energy storage function of the large capacitor makes the circuit have enough energy to convert into powerful audio output when the sudden big signal comes. At this time, the function of large capacitor is a bit like a reservoir, which makes the original turbulent water flow output smoothly, and can also ensure the supply when a large amount of water is used downstream.

In an electronic circuit, current can only flow when the capacitor is charged. After the charging process, the capacitor can't pass DC, which plays a role of "blocking DC" in the circuit. In circuits, capacitors are usually used for coupling, bypassing, filtering, etc. All of them use its characteristics of "communicating and isolating DC". So why can alternating current pass through a capacitor? Let's first look at the characteristics of alternating current. Alternating current not only changes alternately in direction, but also changes regularly in size. The capacitor is connected to the AC power supply, and the capacitor is constantly charged and discharged, so that the charging current and discharging current which conform to the AC variation law flow in the circuit.

The choice of capacitor involves many problems. The first is the problem of compression resistance. When the voltage across the capacitor exceeds its rated voltage, the capacitor will be broken down and damaged. Generally, the breakdown voltages of electrolytic capacitors are 6.3V, 10V, 16V, 25V, 50V, etc.

Section 3 Sensor

Inductance is not widely used in electronic manufacturing, but it is equally important in circuits. We think that inductance, like capacitance, is also an energy storage element, which can convert electric energy into magnetic field energy and store it in the magnetic field. Inductance is represented by the symbol L, and its basic unit is Henry (H), commonly used as milli-Hen (mH). It often forms LC filters, LC oscillators, etc. together with capacitors. In addition, people also use the characteristics of inductance to make chokes, transformers, relays and so on.

The characteristics of inductance are just the opposite of capacitance. It has the characteristics of preventing alternating current from passing and allowing direct current to pass.

There are many inductance coils on a small radio, almost all of which are hollow coils wound with enameled wires, or wound on the iron core and iron core of the skeleton. There are antenna coil (made of enameled wire wound on a magnetic bar), intermediate frequency transformer (commonly known as mid-week), input and output transformer and so on.

The physical diagram and circuit symbols are shown in the figure.

The transformer consists of iron core and copper coil conductor wound on the insulating skeleton. The insulated copper wire is wound on the plastic skeleton, and each skeleton needs to be wound with two sets of coils for input and output. The middle of the coil is isolated with insulating paper. After winding, many iron chips are inserted in the middle of the plastic skeleton. In this way, the inductance of the coil can be significantly increased. Transformer uses the principle of electromagnetic induction to transfer electric energy from one winding to another. Transformer plays an important role in the circuit: coupling AC signal to block DC signal and change the voltage ratio of input and output; The impedance at both ends of the circuit is well matched by the transformer to obtain the maximum transmitted signal power.

Power transformer is to turn high-voltage electricity into civil commercial electricity, and many of our electrical appliances are powered by low-voltage DC. It is necessary to use power transformer to convert 220V AC commercial power into low-voltage AC power, and then use diode rectification and capacitor filtering to form DC power supply. The TV picture tube needs tens of thousands of volts to work, which is provided by the "line output transformer"

Of course, power transformers also have many shortcomings, such as power is proportional to volume, large volume and low efficiency, and are being replaced by new "electronic transformers". Electronic transformers are generally "switching power supplies", and several groups of voltages required for computer work are provided by switching power supplies, which are used in color TVs and monitors without exception.

Relay is an electromechanical switch, which is made of enameled copper wire wound around a circular iron core for hundreds to thousands of times. When the current flows in the coil, the circular iron core generates a magnetic field, which attracts the iron plate with the contact piece above the circular iron core, so that it disconnects the first contact and connects the second switch contact. When the coil is de-energized, the iron core loses its magnetism, and the iron plate leaves the iron core due to the elastic action of the copper sheet of the contact, and the connection with the first contact is restored. Therefore, small current can be used to control the switches of other circuits. The whole relay is protected by plastic or plexiglass dust cover, and some are completely sealed to prevent electric shock and oxidation.

First diode

Semiconductor is a kind of material with special properties. It is not completely conductive like a conductor, nor is it conductive like an insulator. It is somewhere in between, so it is called a semiconductor. The two most important elements in semiconductors are silicon and germanium. We often hear about Silicon Valley in America, because there were many semiconductor manufacturers there at first.

Diodes should be regarded as an elder in the family of semiconductor devices. A long time ago, people were keen to assemble a crystal receiver to listen to radio broadcasts. This mineral was later made into crystal diodes.

The most obvious characteristic of diode is unidirectional conduction, which means that current can only pass from one side, but not from the other side (from positive electrode to negative electrode). We use multimeter to measure the common 1N400 1 silicon rectifier diode. When the red stylus is connected to the negative electrode of the diode and the black stylus is connected to the positive electrode of the diode, the stylus will move, indicating that it can conduct electricity. Then the black contact pin is connected to the negative electrode of the diode, and the red contact pin is connected to the positive electrode of the diode. At this time, the pointer of the multimeter does not move at all or only deflects a little, indicating poor conductivity. (In the multimeter, the black probe is connected to the positive pole of the internal battery. )

The figure shows several common diodes. Among them, there are glass packaging, plastic packaging and metal packaging. Fig. 2 is a circuit symbol of a diode. As its name implies, a diode has two electrodes, a positive electrode and a negative electrode. Generally speaking, the polarity is marked on the shell of the diode. Most of them use rings of different colors to represent the negative electrode, and some of them are directly marked with "-". Most high-power diodes are encapsulated in metal, and a nut is fixed on the radiator.

Using the unidirectional conductivity of diodes, diodes are often used as rectifiers to convert alternating current into direct current, that is, only the positive half cycle (or negative half cycle) of alternating current passes through, and then a capacitor is used to filter to form smooth direct current. In fact, the power supply part of many electrical appliances is like this. Diodes are also used as detectors to "detect" useful signals in high-frequency signals. There will be a "detector diode" in the old radio, generally using 2AP9 germanium tube.

There are also several types of diodes. For electronic products, the following diodes are often used: zener diode for voltage stabilization, switching diode for digital circuit, varactor diode for tuning, photodiode and so on. The most common is light emitting diode.

Light-emitting diodes are everywhere in daily life appliances. They can emit light in red, green and Huang San colors, and they have rectangles with diameters of 3mm, 5mm and 2× 5 mm Like ordinary diodes, light-emitting diodes are also made of semiconductor materials, which also have the property of unidirectional conduction, that is, they can emit light only by connecting the two poles. Light-emitting diodes have two more arrows than ordinary diodes to indicate that they can emit light. Light-emitting diodes (LEDs) are usually used to indicate the working state of circuits, which consume much less power and have a much longer life than small bulbs. With light-emitting diodes, you can also form an electronic display screen. The display screen of the stock exchange is composed of light-emitting diode lattice. Just because all colors are composed of red, green and blue, and blue light-emitting diodes have not been mass-produced before, ordinary electronic display screens can't display real colors.

The light-emitting color of light-emitting diodes is generally the same as its own color, but in recent years, transparent light-emitting tubes have appeared, which can also emit red, yellow, green and other colors of light, and we will not know until we are electrified. There are two ways to distinguish the positive and negative electrodes of light-emitting diodes: experimental method and visual method. The experimental method is to electrify to see if it can emit light. If not, the polarity is wrong or the LED is damaged.

Note that LEDs are current-mode devices. Although both ends can emit light by directly connecting the voltage of 3V, it is easy to be damaged. In practical use, a current limiting resistor must be connected in series. According to different models, the working current is generally 1mA to 30ma. In addition, because the turn-on voltage of LED is generally above 1.7V, the battery of 1.5V cannot light LED. Similarly, the general multimeter can't test the LEDs from R× 1 to R× 1K, but R× 10K can light some LEDs because it uses 15V battery.

Looking at the LED with your eyes, you can find that there are two electrodes inside, one is big and the other is small. Generally speaking, the electrode is smaller, the anode of the LED with a shorter head and the cathode of the LED with a larger electrode. If it is a newly bought LED, the longer pin is the positive electrode.

Triode in the second quarter

Semiconductor triode, also known as transistor, is the most important device in electronic circuits. Its main functions are current amplification and switching. As the name implies, a triode has three electrodes. Diode consists of a PN junction, triode consists of two PN junctions, and one electrode used by * * * becomes the base of triode (denoted by letter B). The other two electrodes become the collector (denoted by the letter C) and the emitter (denoted by the letter E). Because of the different combination methods, one is NPN transistor and the other is PNP transistor.

There are many kinds of triodes, and different models have different uses. Transistors are mostly packaged in plastic or metal, and the appearance of common triodes is shown in the figure, which is large and small. There are two kinds of circuit symbols of triode: the electrode with arrow is emitter, the outward arrow is NPN triode, and the inward arrow is PNP transistor. In fact, the direction pointed by the arrow is the direction of current.

90×× series triodes commonly used in electronic production include low-frequency low-power silicon tubes 90 13(NPN), 90 12(PNP), low-noise tubes 90 14(NPN), high-frequency low-power tubes 90 18(NPN) and so on. Their models are usually marked on plastic casings, but they all look the same, and they are all packaged with TO-92 standard. In the old electronic products, you can also see 3DG6 (low-frequency low-power silicon tube) and 3AX3 1 (low-frequency low-power germanium tube), and their models are also printed on the metal shell. Domestic transistors have a set of naming rules, and electronic enthusiasts had better know:

3 in the first part is represented as a triode. The second part represents the material and structure of the device, A: PNP germanium material B: NPN germanium material C: PNP silicon material D: NPN silicon material The third part represents the function, U: photoelectric tube K: switching tube X: low-frequency low-power tube G: high-frequency low-power tube D: low-frequency high-power tube A: high-frequency high-power tube. In addition, 3DJ is a field effect transistor, and BT stands for a special semiconductor element.

Conversion still follows the conservation of energy, it just converts the energy of power supply into the energy of signal. An important parameter of triode is the current amplification factor β. When a small current is applied to the base of the triode, a current β times the injection current can be obtained at the collector, that is, the collector current. The collector current changes with the change of base current, and a small change of base current can cause a huge change of collector current, which is the amplification effect of triode.

Triode can also be used as an electronic switch, and can also form an oscillator with other components.

Section 3 SCR

Thyristor, also known as thyristor, is an element composed of four layers of semiconductors of PNPN, and has three electrodes, anode A, cathode K and control electrode G.

Silicon controlled rectifier can realize the contactless control of alternating current in the circuit, and the small current controls the large current, and there is no spark when it is controlled like a relay, with fast action, long service life and good reliability. It is used in control circuits such as speed regulation, dimming, voltage regulation and temperature regulation.

Silicon controlled rectifier is divided into one-way and two-way with different symbols. One-way SCR has three PN junctions. Two electrodes, called anode and cathode, are drawn from the outermost P electrode and N electrode, and a control electrode is drawn from the middle P electrode.

One-way SCR has its unique characteristics: when the anode is connected with reverse voltage, or when the anode is connected with DC voltage but no voltage is applied to the control electrode, it will not conduct, but when the anode and the control electrode are connected with DC voltage at the same time, it will conduct. Once turned on, the control voltage loses its control function, and it will always be turned on regardless of whether there is a control voltage or not and regardless of the polarity of the control voltage. To turn it off, only the anode voltage can be reduced to a certain critical value or reversed.

The pins of the triac are mostly arranged from left to right in the order of T 1, T2, and g (the electrode pins face down and face the side with characters). When the magnitude or time of the trigger pulse applied to the control electrode G changes, the magnitude of its conduction current can change.

The difference with the unidirectional thyristor is that when the polarity of the trigger pulse on the G pole of the bidirectional thyristor changes, its conduction direction also changes with the polarity change, so that the AC load can be controlled. However, after being triggered, the unidirectional silicon controlled rectifier can only conduct from the anode to the cathode in one direction, so the silicon controlled rectifier can be divided into unidirectional and bidirectional.

Thyristors are commonly used in electronic production, such as MCR- 100 in one direction and TLC336 in two directions.

Section 4 Integrated Circuits

Integrated circuit is a kind of device with certain functions, which integrates transistors, resistors, capacitors and other elements on a silicon substrate by special technology. The English abbreviation is IC, which is also commonly known as chip. Integrated circuits appeared in the 1960s, when only a dozen components were integrated. Later, the integration became higher and higher, and today's P-III came into being.

Integrated circuits can be divided into analog and digital schools according to different functions and uses, and there are countless specific functions, and their applications cover all aspects of human life. Integrated circuits are divided into three categories according to their internal integration: large-scale, medium-scale and small-scale. Its packaging has many forms. "Double in-line" and "Single in-line" are the most common. Soft package ic in consumer electronic products, chip package IC in precision products, etc.

For CMOS IC, special attention should be paid to prevent electrostatic breakdown of IC, and it is best not to use ungrounded soldering iron for welding. When using IC, we should also pay attention to its parameters, such as working voltage, heat dissipation and so on. Digital IC works at +5V, while analog IC works at different voltages. There are various types of integrated circuits, and their naming has certain rules. Generally, it consists of prefix, number and suffix. Prefix indicates the manufacturer and category of the integrated circuit, and suffix is generally used to indicate the packaging form and version code of the integrated circuit. There are many kinds of commonly used integrated circuits, such as low-power audio amplifier LM386, because of different suffixes. LM386N is a product of American National Semiconductor Company, where LM stands for linear circuit and N stands for plastic duplexer. The following are the trademarks and device model prefixes of major IC production companies.

There are many kinds of integrated circuits. With the development of technology, more and more powerful integrated circuits have appeared, which brings convenience to the production of electronic products. When designing and manufacturing, if there is no application-specific integrated circuit, we should try our best to choose a widely used general integrated circuit, taking into account the price and manufacturing complexity of the integrated circuit. In electronic production, there are many commonly used integrated circuits, such as NE555 (time base circuit), LM324 (four-channel integrated operational amplifier), TDA2822 (dual-channel low-power amplifier), KD9300 (single-music integrated circuit), LM3 17 (three-terminal adjustable voltage regulator) and so on.

Section 1 Three-terminal Stable Integrated Circuit

Common three-terminal regulated integrated circuits in electronic products include 78×××× series with positive voltage output and 79××××× series with negative voltage output. As the name implies, a three-terminal IC is an integrated circuit for voltage stabilization, which has only three pins to output, namely, an input terminal, a ground terminal and an output terminal. It looks like an ordinary triode, the standard package of TO-220 and the package of TO-92 of 90 13.

Using 78/79 series three-terminal regulated IC to form a regulated power supply requires few peripheral components, and the circuit has protection circuits such as overcurrent, overheating and regulating tube, which is reliable, convenient and cheap to use. The number after 78 or 79 in this series of integrated voltage stabilizing IC models represents the output voltage of the three-terminal integrated voltage stabilizing circuit. For example, 7806 indicates that the output voltage is positive 6V, and 7909 indicates that the output voltage is negative 9V.

78/79 series three-terminal stabilized integrated circuits have been produced by many electronic manufacturers since 1980s, usually prefixed with the manufacturer's code name, such as TA7805 is Toshiba's product and AN7909 is Panasonic's product. (Click here to view the knowledge of prefix identification integrated circuits)

The number 78 or 79 is sometimes followed by an m or l, such as 78M 12 or 79L24, to distinguish the output current from the packaging form, in which the maximum output current of 78L series is 100mA, that of 78M series is 1A, and that of 78 series is1.5a.. How much more? Plastic-sealed voltage stabilizing circuit has the advantages of convenient installation and low price, and is widely used. 79 series except that the output voltage is negative. Except for the different arrangement of stitches, the naming method and appearance are the same as those of the 78 series.

Because the three-terminal fixed integrated voltage stabilizing circuit is easy to use, it is often used in electronic production, which can be used to modify the voltage stabilizing power supply of discrete components and often used as the working power supply of electronic equipment. The circuit diagram is shown in the figure.

Note that the input, output and grounding terminals of the three-terminal integrated voltage stabilizing circuit must not be connected wrongly, otherwise it is easy to burn out. Generally, the minimum voltage difference between the input and output of a three-terminal integrated voltage regulator circuit is about 2V, otherwise a stable voltage cannot be output. The voltage difference should generally be kept at 4-5V, that is, the voltage after transformer transformation, diode rectification and capacitor filtering should be higher than the specified value.

In practical application, a large enough radiator should be installed on the three-terminal integrated voltage stabilizing circuit (of course, it is not needed in the case of low power). When the temperature of the voltage stabilizing tube is too high, the voltage stabilizing performance will deteriorate or even be damaged.

When a regulated power supply that can output more than 1.5A is needed in production, several three-terminal regulated circuits are usually connected in parallel, so that the maximum output current is n1.5a. However, in application, it should be noted that the integrated regulated circuits used in parallel should adopt the same batch of products from the same manufacturer to ensure the consistency of parameters. In addition, there is a certain margin in the output current to avoid the chain combustion of other circuits when individual integrated voltage stabilizing circuits fail.

Section 2 Voice Integrated Circuit

Music integrated circuits and language integrated circuits are often used in electronic production, which are generally called language films and music films. They are generally soft-packed, that is, the chip is directly encapsulated on a small circuit board with vinyl. Voice IC generally needs a small number of peripheral components to work, and can be directly soldered on this circuit board.

Although the voice IC application circuit is simple, it is really an integrated circuit with thousands of transistor cores. It includes oscillator, metronome, timbre generator, ROM, address calculator and control output circuit. A musical can store one or more world famous songs, and the price is very cheap, a few cents. Music doorbells are all made of this kind of music film, but the cost is actually very low.

Different language films store all kinds of animal calls, short languages and so on. And the price is more expensive than musicals. But because it's interesting, there are more and more applications. Talking calculator, reversing alarm, alarm clock, etc. Although there are many kinds of voice circuits, they can't make sounds according to users' requirements at any time, because commercial voice products use mask technology, and the sound they make is dead, which controls the cost.

Generally, manufacturers of voice integrated circuits can customize the content of voice, but for shielding reasons, the number is required to be more than a thousand pieces. In recent years, OTP voice circuit has solved this problem. OTP means one-time programmable, that is, the chip produced by the manufacturer is empty and the content is written by the user (the equipment needs to be developed). Once cured, it cannot be erased and information will not be lost. Its appearance provides convenience for developers to trial-produce prototypes, especially suitable for small batch production.

It is very convenient to use recordable language circuits in amateur production, such as UM5506, ISD 1400, ISD2500, etc. , less peripheral components. Bitbaby first learned about integrated circuits that can record and play voice, which was in radio magazines for more than 90 years. I remember UM5 10 1 and T6668, all using DRAM such as 4 1256. At that time, I wanted to have a set of monsters that could record without tapes, and I could change my tune at will when playing. Early digital transponders also used them. Because DRAM is used, if there is no spare battery, all information will be lost once the power is cut off.