First transistor
In the photo on the right you can see the first working transistor, which was created in 1947 by three scientists - Walter Brattain, John Bardeen and William Shockley.
Despite the fact that the first transistor was not very presentable, this did not stop it from revolutionizing electronics.
It is difficult to imagine what the current civilization would be like if the transistor had not been invented.
The transistor is the first solid-state device capable of amplifying, generating and converting an electrical signal. It has no vibration-prone parts and is compact in size. This makes it very attractive for electronics applications.
This was a small introduction, but now let's take a closer look at what a transistor is.
First, it is worth recalling that transistors are divided into two large classes. The first includes the so-called bipolar, and the second - field (they are also unipolar). The basis of both field-effect and bipolar transistors is a semiconductor. The main material for the production of semiconductors is germanium and silicon, as well as a compound of gallium and arsenic - gallium arsenide ( GaAs).
It is worth noting that silicon-based transistors are most widespread, although this fact may soon be shaken, as technology development is ongoing.
It just so happened, but at the beginning of the development of semiconductor technology, the bipolar transistor took the lead. But not many people know that initially the stake was placed on the creation of a field-effect transistor. It was brought to mind later. Read about MOSFET field-effect transistors.
We will not go into a detailed description of the device of the transistor at the physical level, but first we will find out how it is indicated on the schematic diagrams. For beginners in electronics, this is very important.
First, it must be said that bipolar transistors can be of two different structures. This is the structure of P-N-P and N-P-N. While we will not go into theory, just remember that a bipolar transistor can have either a P-N-P or N-P-N structure.
In schematic diagrams, bipolar transistors are designated like this.
As you can see, the figure shows two conventional graphic symbols. If the arrow inside the circle is directed to the center line, then this is a P-N-P transistor. If the arrow is directed outward, then it has an N-P-N structure.
A little advice.
In order not to memorize the symbol, and immediately determine the type of conductivity (p-n-p or n-p-n) of a bipolar transistor, you can apply this analogy.
First, let's look where the arrow is pointing in the conventional image. Further, we imagine that we are walking in the direction of the arrow, and if we run into a “wall” - a vertical line - then, it means, “Pass Hem "! " Hem "- means p- n-p (n- H-P ).
Well, if we go and do not run into the "wall", then the diagram shows an n-p-n transistor. A similar analogy can be used for field-effect transistors when determining the type of channel (n or p). Read about the designation of different field-effect transistors in the diagram
Usually discrete, that is, a separate transistor has three terminals. Previously, it was even called a semiconductor triode. Sometimes it can have four pins, but the fourth is used to connect the metal case to a common wire. It is shielding and is not linked to other leads. Also, one of the conclusions, usually a collector (we will talk about it later), can be in the form of a flange for attaching to a cooling radiator or be part of a metal case.
Take a look. The photo shows various transistors of Soviet production, as well as the early 90s.
But this is a modern import.
Each of the terminals of the transistor has its own purpose and name: base, emitter and collector. Usually these names are abbreviated and written simply B ( Base), E ( Emitter), K ( Collector). On foreign circuits, the collector output is marked with the letter C, this is from the word Collector - "collector" (verb Collect - "collect"). The base output is marked as B, from the word Base (from the English Base - "main"). This is the control electrode. Well, and the output of the emitter is denoted by the letter E, from the word Emitter - "issuer" or "source of emissions". In this case, the emitter serves as a source of electrons, so to speak, a supplier.
The terminals of the transistors must be soldered into the electronic circuit, strictly observing the pinout. That is, the output of the collector is soldered exactly to that part of the circuit where it should be connected. It is impossible to solder the collector or emitter output instead of the base output. Otherwise the circuit will not work.
How to find out where on the schematic diagram the transistor has a collector, and where is the emitter? It's simple. The output with the arrow is always the emitter. The one that is drawn perpendicular (at an angle of 90 0) to the center line is the base pin. And the one that remained is the collector.
Also on the schematic diagrams, the transistor is marked with the symbol VT or Q... In old Soviet books on electronics, you can find the designation in the form of a letter V or T... Next, the serial number of the transistor in the circuit is indicated, for example, Q505 or VT33. It should be borne in mind that the letters VT and Q denote not only bipolar transistors, but also field-effect transistors.
In real electronics, transistors can be easily confused with other electronic components, for example, triacs, thyristors, integrated stabilizers, since they have the same package. It is especially easy to get confused when unknown markings are applied to an electronic component.
In this case, you need to know that on many printed circuit boards, positioning is marked and the type of element is indicated. This is the so-called silk screen printing. So Q305 can be written on the PCB next to the part. This means that this element is a transistor and its serial number in the circuit diagram is 305. It also happens that the name of the transistor electrode is indicated next to the terminals. So, if there is the letter E next to the output, then this is the emitter electrode of the transistor. Thus, you can purely visually determine what is installed on the board - a transistor or a completely different element.
As already mentioned, this statement is true not only for bipolar transistors, but also for field-effect ones. Therefore, after determining the type of element, it is necessary to clarify the class of the transistor (bipolar or field-effect) according to the marking applied to its case.
Field-effect transistor FR5305 on the printed circuit board of the device. The element type is indicated next to it - VT
Any transistor has its own type or marking. Marking example: KT814. By it you can find out all the parameters of the element. As a rule, they are indicated in the datasheet. It is also a reference sheet or technical documentation. There may also be transistors of the same series, but with slightly different electrical parameters. Then the name contains additional characters at the end, or, less often, at the beginning of the marking. (for example, the letter A or D).
Why bother with all sorts of additional designations? The fact is that in the production process it is very difficult to achieve the same characteristics for all transistors. There is always a certain, albeit small, but difference in the parameters. Therefore, they are divided into groups (or modifications).
Strictly speaking, the parameters of transistors of different batches can differ quite significantly. This was especially noticeable earlier, when the technology of their mass production was only being refined.
Now let's find out about what field-effect transistors are. Field effect transistors are very common in both old circuitry and modern ones. Nowadays, devices with an insulated gate are used to a greater extent; today we will talk about the types of field-effect transistors and their features. In the article I will make a comparison with bipolar transistors, in separate places.
Definition
A field-effect transistor is a fully controlled semiconductor switch, controlled by an electric field. This is the main difference in terms of practice from bipolar transistors, which are controlled by current. The electric field is created by the voltage applied to the gate relative to the source. The polarity of the control voltage depends on the type of transistor channel. There is a good analogy here with electronic vacuum tubes.
Another name for field-effect transistors is unipolar. "UNO" means one. In field-effect transistors, depending on the type of channel, the current is carried out by only one type of carriers, holes or electrons. In bipolar transistors, the current was formed from two types of charge carriers - electrons and holes, regardless of the type of devices. Field-effect transistors can generally be divided into:
transistors with a control p-n-junction;
insulated gate transistors.
Both of them can be n-channel and p-channel, a positive control voltage must be applied to the gate of the former to open the key, and for the latter, negative with respect to the source.
All types of field-effect transistors have three leads (sometimes 4, but rarely, I met only on Soviet ones and it was connected to the case).
1. Source (source of charge carriers, analogue of a bipolar emitter).
2. Drain (receiver of charge carriers from the source, analog of the collector of a bipolar transistor).
3. Shutter (control electrode, analogue of a grid on lamps and a base on bipolar transistors).
Pn junction transistor
The transistor consists of the following areas:
4. Shutter.
In the image you can see the schematic structure of such a transistor, the leads are connected to the metallized sections of the gate, source and drain. In a specific circuit (this is a p-channel device), the gate is an n-layer, has less resistivity than the channel region (p-layer), and the p-n-junction region is located more in the p-region for this reason.
a - n-type field-effect transistor, b - p-type field-effect transistor
To make it easier to remember, remember the notation for the diode, where the arrow points from the p-region to the n-region. Here also.
The first state is to apply external tension.
If a voltage is applied to such a transistor, a plus to the drain, and a minus to the source, a large current will flow through it, it will be limited only by the channel resistance, external resistances and the internal resistance of the power source. An analogy can be made with a normally closed key. This current is called Istart or the initial drain current at Uz \u003d 0.
A field effect transistor with a control pn junction, without a control voltage applied to the gate, is as open as possible.
The voltage is applied to the drain and source in this way:
The main charge carriers are introduced through the source!
This means that if the transistor is p-channel, then the positive terminal of the power supply is connected to the source, since the main carriers are holes (positive charge carriers) - this is the so-called hole conductivity. If the transistor is n-channel, connect the negative terminal of the power supply to the source, because in it, the main charge carriers are electrons (negative charge carriers).
Source - the source of the main charge carriers.
Here are the simulation results for such a situation. On the left is a p-channel transistor, and on the right, an n-channel transistor.
The second state - we apply voltage to the gate
When a positive voltage is applied to the gate relative to the source (Uzi) for the p-channel and negative for the n-channel, it is shifted in the opposite direction, the p-n-junction region expands towards the channel. As a result, the channel width decreases, the current decreases. The gate voltage at which the current through the switch stops flowing is called the cutoff voltage.
Cut-off voltage has been reached and the key is fully closed. The picture with the simulation results shows such a state for the p-channel (left) and n-channel (right) dongle. By the way, in English, such a transistor is called JFET.
The operating mode of the transistor at a voltage Uzi is either zero or reverse. Due to the reverse voltage, it is possible to "cover the transistor", it is used in class A amplifiers and other circuits where smooth regulation is needed.
The cut-off mode occurs when Uzi \u003d U cutoff for each transistor, it is different, but in any case it is applied in the opposite direction.
Characteristics, VAC
The output characteristic is called a graph that shows the dependence of the drain current on Ussi (applied to the drain and source terminals), at different gate voltages.
It can be broken down into three areas. At first (on the left side of the graph) we see the ohmic region - in this gap the transistor behaves like a resistor, the current increases almost linearly, reaching a certain level, goes into the saturation region (in the center of the graph).
On the right side of the graph, we see that the current starts to rise again, this is the breakdown area, the transistor should not be here. The uppermost branch shown in the figure is the current at zero Uzi, we see that the current is the largest here.
The higher the voltage Uzi, the lower the drain current. Each of the branches differs by 0.5 volts at the gate. Which we have confirmed by modeling.
Shown here is the drain-gate characteristic, i.e. dependence of the drain current on the voltage at the gate at the same drain-source voltage (in this example 10V), here the grid step is also 0.5V, we again see that the closer the voltage Uzi to 0, the greater the drain current.
In bipolar transistors there was such a parameter as the current transfer coefficient or the gain, it was designated as B or H21e or Hfe. In the field, the slope is denoted by the letter S to indicate the ability to amplify voltage.
That is, the slope shows how much milliAmpere (or Ampere) the drain current grows with an increase in the gate-source voltage by the number of Volts with a constant drain-source voltage. It can be calculated based on the drain-gate characteristic, in the example above, the slope is about 8 mA / V.
Connection diagrams
As with bipolar transistors, there are three typical switching circuits:
1.With a common source (a). It is used most often, it gives amplification in current and power.
2. With a common shutter (b). Rarely used, low input impedance, no gain.
3.With a common drain (c). The voltage gain is close to 1, the input impedance is large, and the output impedance is low. Another name is the source follower.
Features, advantages, disadvantages
- practically does not consume control current,this is reduces control loss, signal distortion,signal source overcurrent ...
The main advantage of the field-effect transistor high input impedance... Input impedance is the ratio of current to gate-source voltage. The principle of operation lies in the control by means of an electric field, and it is formed when a voltage is applied. I.e field-effect transistors are voltage controlled.
Average frequency characteristics of field-effect transistors are better than that of bipolar, this is due to the fact that it takes less time to "dissipate" charge carriers in the regions of the bipolar transistor. Some modern bipolar transistors can be superior to field-effect transistors, this is due to the use of more advanced technologies, reducing the base width, and so on.
The low noise level of field-effect transistors is due to the absence of the charge injection process, as in bipolar ones.
Stability with temperature changes.
Low power consumption in a conducting state - more efficiency of your devices.
The simplest example of using high input impedance is matching devices for connecting electric acoustic guitars with piezo pickups and electric guitars with electromagnetic pickups to line inputs with low input impedance.
Low input impedance can cause signal dips, distorting its shape to varying degrees depending on the frequency of the signal. This means that you need to avoid this by introducing a stage with a high input impedance. Here is the simplest diagram of such a device. Suitable for connecting electric guitars to the line-in of a computer audio card. With it, the sound will become brighter and the timbre richer.
The main disadvantage is that such transistors are afraid of static. You can take an element with electrified hands, and it will immediately fail, this is a consequence of controlling the key using the field. It is recommended to work with them in dielectric gloves, connected through a special wristband to ground, with a low-voltage soldering iron with an insulated tip, and the terminals of the transistor can be wired to short-circuit them during installation.
Modern devices are practically not afraid of this, since protective devices such as zener diodes can be built into them at the entrance, which are triggered when the voltage is exceeded.
Sometimes novice radio amateurs have fears reaching the point of absurdity, such as putting on foil hats on their heads. Although everything described above is mandatory, non-observance of any conditions does not guarantee the failure of the device.
Insulated Gate Field Effect Transistors
This type of transistors is actively used as semiconductor controlled switches. Moreover, they work most often in the key mode (two positions "on" and "off"). They have several names:
1. MIS-transistor (metal-dielectric-semiconductor).
2. MOS transistor (metal oxide semiconductor).
3. MOSFET-transistor (metal-oxide-semiconductor).
Remember - these are just variations of one name. The dielectric, or oxide as it is also called, acts as an insulator for the gate. In the diagram below, the insulator is shown between the n-region near the gate and the gate in the form of a white area with dots. It is made of silicon dioxide.
The dielectric eliminates electrical contact between the gate electrode and the substrate. Unlike the control pn junction, it works not on the principle of the expansion of the junction and blocking the channel, but on the principle of changing the concentration of charge carriers in a semiconductor under the action of an external electric field. MOSFETs are of two types:
1. With a built-in channel.
2.With an induced channel
In the diagram, you see a transistor with an embedded channel. From it you can already guess that the principle of its operation resembles a field-effect transistor with a control p-n-junction, i.e. when the gate voltage is zero, current flows through the switch.
Two regions with an increased content of impurity charge carriers (n +) with increased conductivity are created near the source and drain. The substrate is called a P-type base (in this case).
Please note that the crystal (substrate) is connected to the source, in many conventional graphic symbols it is drawn this way. As the gate voltage increases, a transverse electric field appears in the channel, it repels charge carriers (electrons) and the channel closes when the threshold Uzi is reached.
When a negative gate-source voltage is applied, the drain current drops, the transistor begins to close - this is called depletion mode.
When a positive voltage is applied to the gate-source, the opposite process occurs - electrons are attracted, the current increases. This is the enrichment regime.
All of the above is true for MOSFETs with an embedded N-channel. If a p-type channel replaces all the words "electrons" with "holes", the polarities of the voltage are reversed.
According to the datasheet for this transistor, the gate-source threshold voltage is around one volt, and its typical value is 1.2 V, let's check it out.
The current became in microamperes. If you increase the voltage a little more, it will disappear completely.
I picked a transistor at random and came across a fairly sensitive device. I will try to change the voltage polarity so that there is a positive potential on the gate, check the enrichment mode.
With a gate voltage of 1V, the current increased four times compared to what it was at 0V (first picture in this section). It follows from this that, unlike the previous type of transistors and bipolar transistors, it can work both to increase the current and to decrease it without additional strapping. This statement is very crude, but as a first approximation it has a right to exist.
Everything here is almost the same as in a transistor with a control transition, except for the presence of an enrichment mode in the output characteristic.
The drain-gate characteristic clearly shows that the negative voltage causes the depletion and closing of the key, and the positive voltage at the gate causes the enrichment and greater opening of the key.
MOS transistors with an induced channel do not conduct current in the absence of a voltage at the gate, or rather, there is current, but it is extremely small, because this is the reverse current between the substrate and the highly doped drain and source portions.
The field-effect transistor with an insulated gate and an induced channel is analogous to a normally open switch, no current flows.
In the presence of a gate-source voltage, since we consider the n-type of the induced channel, then the voltage is positive, under the action of the field, negative charge carriers are attracted to the gate region.
This is how a "corridor" appears for electrons from source to drain, thus a channel appears, the transistor opens, and current begins to flow through it. We have a p-type substrate, in it the main ones are positive charge carriers (holes), there are very few negative carriers, but under the action of the field they detach from their atoms, and their movement begins. Hence the lack of conductivity in the absence of voltage.
The output characteristic exactly repeats the same for the previous ones, the only difference is that the Uzi voltages become positive.
The drain-gate characteristic shows the same, the differences are again in the gate voltages.
When considering current-voltage characteristics, it is extremely important to carefully look at the values \u200b\u200bwritten along the axes.
A voltage of 12 V was applied to the key, and at the gate we have 0. The current does not flow through the transistor.
This means that the transistor is completely open, if it were not there, the current in this circuit would be 12/10 \u003d 1.2 A. Later I studied how this transistor works, and found out that at 4 volts it starts to open.
Adding 0.1V each, I noticed that with every tenth of a volt the current grows more and more, and by 4.6 Volts the transistor is almost completely open, the difference with the gate voltage of 20V in the drain current is only 41 mA, at 1.1 A it is nonsense.
This experiment reflects the fact that the induced channel transistor only opens when the threshold voltage is reached, which allows it to work perfectly as a switch in pulsed circuits. Actually, the IRF740 is one of the most common.
The results of measurements of the gate current showed that indeed field-effect transistors almost do not consume the control current. With a voltage of 4.6 volts, the current was only 888 nA (nano !!!).
At 20V, it was 3.55 μA (micro). A bipolar transistor would have it on the order of 10 mA, depending on the gain, which is tens of thousands of times more than that of a field-effect transistor.
Not all keys open with such voltages, this is due to the design and features of the circuitry of the devices where they are used.
A discharged capacity at the first moment of time requires a large charging current, and even rare control devices (PWM controllers and microcontrollers) have strong outputs, therefore they use drivers for field gates, both in field effect transistors and in (bipolar with an insulated gate). This is an amplifier that converts the input signal into an output of such magnitude and current strength, sufficient to turn the transistor on and off. The charging current is also limited by a resistor in series with the gate.
In this case, some gates can also be controlled from the microcontroller port through a resistor (the same IRF740). We touched on this topic.
They resemble field-effect transistors with a control gate, but differ in that on the UGO, as in the transistor itself, the gate is separated from the substrate, and the arrow in the center indicates the type of channel, but is directed from the substrate to the channel, if it is an n-channel mosfet - towards the shutter and vice versa.
For keys with an induced channel:
It might look like this:
Pay attention to the English-language names of the pins, they are often indicated in datasheets and on diagrams.
For keys with an embedded channel:
Transistor (from english words tran (sfer) - transfer and (re) sistor - resistance) - a semiconductor device designed to amplify, generate and convert electrical oscillations. The most common are the so-called bipolar transistors... The electrical conductivity of the emitter and collector is always the same (p or n), the base is the opposite (n or p). In other words, a bipolar transistor contains two pn junctions: one of them connects the base to the emitter (emitter junction), the other - to the collector (collector junction).
The letter code of the transistors is the Latin letters VT. In the diagrams, these semiconductor devices are designated as shown in fig. 8.1 ... Here, a short dash with a line from the middle symbolizes the base, two oblique lines drawn to its edges at an angle of 60 ° - the emitter and the collector. The electrical conductivity of the base is judged by the symbol of the emitter: if its arrow is directed towards the base (see. fig. 8.1, VT1), this means that the emitter has an electrical conductivity of the p type, and the base of the n type; if the arrow is directed in the opposite direction (VT2), the electrical conductivity of the emitter and base is reversed.
Knowing the electrical conductivity of the base emitter and collector is necessary in order to properly connect the transistor to the power source. In reference books, this information is given in the form of a structural formula. A transistor, the base of which has an electrical conductivity of type n, is denoted by the formula pnp, and a transistor with a base having a conductivity of type p is denoted by the formula npn. In the first case, a negative voltage with respect to the emitter should be applied to the base and the collector, in the second - positive.
For clarity, the conventional graphic designation of a discrete transistor is usually placed in a circle symbolizing its case. Sometimes a metal case is connected to one of the terminals of the transistor. In the diagrams, this is shown by a dot at the intersection of the corresponding pin with the frame symbol. If the case is equipped with a separate terminal, the terminal line may be connected to a circle without a dot (VT3 on fig. 8.1). In order to increase the information content of the circuits, it is allowed to indicate its type next to the positional designation of the transistor.
The electrical communication lines from the emitter and the collector are carried out in one of two directions: perpendicular or parallel to the base output (VT3-VT5). A break in the base pin is allowed only at a certain distance from the body symbol (VT4).
A transistor can have several emitter regions (emitters). In this case, the emitter symbols are usually depicted on one side of the base symbol, and the body designation circle is replaced with an oval ( fig. 8.1, VT6).
The standard allows transistors to be depicted without a case symbol, for example, when depicting unpackaged transistors or when it is necessary to show the transistors that are part of an assembly of transistors or an integrated circuit.
Since the letter code VT is provided to designate transistors made in the form of an independent device, the transistors of the assemblies are designated in one of the following ways: either use the VT code and assign them serial numbers along with other transistors (In this case, such an entry is placed on the circuit field: VT1-VT4 K159NT1), or use the code of analog microcircuits (DA) and indicate the belonging of the transistors in the assembly in the reference designation ( fig. 8.2, DA1.1, DA1.2). The terminals of such transistors, as a rule, are given a conditional numbering assigned to the terminals of the case in which the matrix is \u200b\u200bmade.
Without the symbol of the case, transistors of analog and digital microcircuits are shown on the circuits (for example, on fig. 8.2 transistors of the p-p-p structure with three and four emitters are shown).
Graphic symbols for some types of bipolar transistors are obtained by introducing special characters into the main symbol. So, to depict an avalanche transistor, a sign of the avalanche breakdown effect is placed between the symbols of the emitter and collector (see. fig. 8.3, VT1, VT2). When turning the UGO, the position of this sign must remain unchanged.
The UGO of a single-junction transistor is built differently: it has one pn-junction, but two base outputs. The emitter symbol in the UGO of this transistor is carried out to the middle of the base symbol ( fig. 8.3, VT3, VT4). The electrical conductivity of the latter is judged by the emitter symbol (arrow direction).
The UGO of a large group of p-n-junction transistors, called field... The basis of such a transistor is a channel with n or p-type electrical conductivity, created in a semiconductor and equipped with two terminals (source and drain). The channel resistance is controlled by the third electrode - the gate. The channel is depicted in the same way as the base of a bipolar transistor, but placed in the middle of the circle-case ( fig. 8.4, VT1), the source and drain symbols are connected to it on one side, the gate - on the other side on the continuation of the source line. The conductivity of the channel is indicated by an arrow on the gate symbol (on fig. 8.4 conventional graphic designation VT1 symbolizes a transistor with an n-type channel, VT1 - with a p-type channel).
In the conventional graphic designation of field-effect transistors with an insulated gate (it is depicted by a dash parallel to the symbol of the channel with an output on the continuation of the source line), the electrical conductivity of the channel is shown by an arrow placed between the symbols of the source and drain. If the arrow is directed towards the channel, then this means that a transistor with an n-type channel is shown, and if in the opposite direction (see. fig. 8.4, VT3) - with a p-type channel. Do the same in the presence of an output from the substrate (VT4), as well as when displaying a field-effect transistor with a so-called induced channel, the symbol of which is three short dashes (see. fig. 8.4, VT5, VT6). If the substrate is connected to one of the electrodes (usually with a source), this is shown inside the UGO without a point (VT1, VT8).
A field effect transistor can have multiple gates. They are depicted with shorter dashes, and the output line of the first gate must be placed on the continuation of the source line (VT9).
Field-effect transistor leads are allowed exile [censorship] only at a certain distance from the case symbol (see. fig. 8.4, VT2). In some types of field-effect transistors, the case can be connected to one of the electrodes or have an independent output (for example, transistors of the KPZ03 type).
Of transistors controlled by external factors, they are widely used phototransistors... As an example on fig. 8.5 shows the conventional graphic designations of phototransistors with a base output (FT1, VT2) and without it (K73). Along with other semiconductor devices, the action of which is based on the photoelectric effect, phototransistors can be part of optocouplers. In this case, the UGO of the phototransistor, together with the UGO of the emitter (usually an LED), is enclosed in a housing symbol that unites them, and the photoelectric effect sign - two oblique arrows are replaced with arrows perpendicular to the base symbol.
For example on fig. 8.5 depicts one of the optocouplers of a dual optocoupler (this is indicated by the positional designation U1.1), Similarly, the UHO optocoupler with a composite transistor (U2) is built.
If you have just started to understand radio engineering, I will talk about that in this article, how the radio components are indicated on the diagram, what are they called on it, and what appearance they have.
Here you will find out how a transistor, diode, capacitor, microcircuit, relay, etc. are indicated.
Please click for more details.
How is a bipolar transistor denoted
All transistors have three terminals, and if it is bipolar, then there are two types, as can be seen from the image of the PNP transition and the PNN transition. And three pins are named e-emitter, k-collector and b-base. Where is what pin on the transistor itself is looked for in the directory, or enter the name of the transistor + pins in the search.
The transistor has the following appearance, and this is only a small part of their appearance, the existing denominations are complete.
How the polar transistor is indicated
There are already three pins that have the following names, these are s-gate, i-source, s-drain
But the appearance visually differs little, or rather it may have the same base. The question is how to find out what kind of base it is, and this is already from reference books or the Internet by the designation written on the base.
How the capacitor is indicated
Capacitors are both polar and non-polar.
The difference between their designation is that one of the terminals is indicated on the polar one with a "+" and the capacitance is measured in microfarads "microfarads".
And they have such an appearance, it should be borne in mind that if the capacitor is polar, then on the base on one of the sides of the legs an output is indicated, only this time it is basically the sign "-".
How diode and LED are indicated
The designation of the LED and diode on the diagram differs in that the LED is enclosed and two arrows emerge. But their role is different - the diode serves to rectify the current, and the LED is already for emitting light.
And LEDs have such an appearance.
And this kind of conventional rectifier and pulse diodes for example:
How the microcircuit is indicated.
Microcircuits are a smaller circuit that performs one function or another, while they can have a large number of transistors.
And they have such an appearance.
Relay designation
First of all, I think about them motorists heard, especially drivers of Zhiguli.
Since when there were no injectors and transistors were not widespread, headlights, a cigarette lighter, a starter, and everything in it were almost turned on and controlled through a relay in a car.
This is the simplest relay circuit.
Everything is simple here, a current of a certain voltage is supplied to the electromagnetic coil, and that, in turn, closes or opens a section of the circuit.
This concludes the article.
If you want what radio parts you want to see in the next article, write in the comments.
The ability to read electrical circuits is an important component, without which it is impossible to become a specialist in the field of electrical work. Every novice electrician must know how sockets, switches, switching devices and even an electricity meter are indicated on the wiring project in accordance with GOST. Further, we will provide the readers of the site with symbols in electrical circuits, both graphical and alphabetic.
Graphic
As for the graphic designation of all elements used in the diagram, we will provide this overview in the form of tables, in which the products will be grouped by purpose.
In the first table, you can see how the electrical boxes, boards, cabinets and consoles are marked on the wiring diagrams:
The next thing you need to know is the conventional designation of power outlets and switches (including walk-through switches) on single-line diagrams of apartments and private houses:
As for lighting elements, lamps and lamps according to GOST indicate as follows:
In more complex circuits, where electric motors are used, elements such as:
It is also useful to know how transformers and chokes are graphically indicated on basic wiring diagrams:
Electrical measuring instruments in accordance with GOST have the following graphic designations in the drawings:
And here, by the way, is a table useful for novice electricians, which shows how the ground loop looks on the wiring plan, as well as the power line itself:
In addition, on the diagrams you can see a wavy or straight line, "+" and "-", which indicate the type of current, voltage and pulse shape:
In more complex automation schemes, you may encounter incomprehensible graphic symbols, such as contact connections. Remember how these devices are indicated on the wiring diagrams:
In addition, you should be aware of how radioelements look on projects (diodes, resistors, transistors, etc.):
That's all the conventionally graphic designations in electrical circuits of power circuits and lighting. As you have already seen for yourself, there are quite a few components and you can remember how each is designated only with experience. Therefore, we recommend that you keep all these tables for yourself, so that when reading the project of the layout of the wiring of a house or apartment, you can immediately determine what kind of circuit element is in a certain place.
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