A zener diode is a semiconductor diode with unique properties. If an ordinary semiconductor, when turned back on, is an insulator, then it performs this function until a certain increase in the applied voltage, after which an avalanche-like reversible breakdown occurs. With a further increase in the reverse current flowing through the zener diode, the voltage continues to remain constant due to a proportional decrease in resistance. In this way it is possible to achieve a stabilization regime.
In the closed state, a small leakage current initially passes through the zener diode. The element behaves like a resistor, the value of which is high. During breakdown, the resistance of the zener diode becomes insignificant. If you continue to increase the voltage at the input, the element begins to heat up and when the current exceeds the permissible value, an irreversible thermal breakdown occurs. If the matter is not brought to this point, when the voltage changes from zero to the upper limit of the working area, the properties of the zener diode are preserved.
When a zener diode is directly switched on, the characteristics are no different from a diode. When the plus is connected to the p-region and the minus to the n-region, the junction resistance is low and current flows freely through it. It increases with increasing input voltage.
A zener diode is a special diode, mostly connected in the opposite direction. The element is initially in the closed state. When an electrical breakdown occurs, the voltage zener diode maintains it constant over a wide current range.
Minus is applied to the anode, and plus is applied to the cathode. Beyond stabilization (below point 2), overheating occurs and the likelihood of element failure increases.
The parameters of the zener diodes are as follows:
Unlike a conventional diode, a zener diode is a semiconductor device in which the areas of electrical and thermal breakdown are located quite far from each other on the current-voltage characteristic.
Associated with the maximum permissible current is a parameter often indicated in tables - power dissipation:
P max = I st max ∙ U st.
The dependence of the zener diode operation on temperature can be either positive or negative. By connecting elements in series with coefficients of different signs, precision zener diodes are created that are independent of heating or cooling.
A typical circuit of a simple stabilizer consists of a ballast resistance R b and a zener diode that shunts the load.
In some cases, stabilization is disrupted.
To protect the stabilizer, thyristor protection circuits or
Resistor R b is calculated by the formula:
R b = (U pit - U nom)(I st + I n).
Zener diode current I st is selected between the permissible maximum and minimum values, depending on the input voltage U supply and load current I n.
The elements have a large spread in stabilization voltage. To obtain the exact value of U n, zener diodes are selected from the same batch. There are types with a narrower range of parameters. For high power dissipation, the elements are installed on radiators.
To calculate the parameters of a zener diode, initial data is required, for example, the following:
The parameters are typical for devices with low energy consumption.
For a minimum input voltage of 12 V, the load current is selected to the maximum - 100 mA. Using Ohm's law, you can find the total load of the circuit:
R∑ = 12 V / 0.1 A = 120 Ohm.
The voltage drop across the zener diode is 9 V. For a current of 0.1 A, the equivalent load will be:
R eq = 9 V / 0.1 A = 90 Ohm.
Now you can determine the ballast resistance:
R b = 120 Ohm - 90 Ohm = 30 Ohm.
It is selected from the standard series, where the value coincides with the calculated one.
The maximum current through the zener diode is determined taking into account the load disconnection, so that it does not fail if any wire is unsoldered. The voltage drop across the resistor will be:
U R = 15 - 9 = 6 V.
Then the current through the resistor is determined:
I R = 6/30 = 0.2 A.
Since the zener diode is connected in series, I c = I R = 0.2 A.
The dissipation power will be P = 0.2∙9 = 1.8 W.
Based on the obtained parameters, a suitable D815V zener diode is selected.
A symmetrical diode thyristor is a switching device that conducts alternating current. A feature of its operation is the voltage drop to several volts when turned on in the range of 30-50 V. It can be replaced by two back-to-back conventional zener diodes. The devices are used as switching elements.
When it is not possible to select a suitable element, an analogue of a zener diode on transistors is used. Their advantage is the ability to regulate voltage. For this purpose, DC amplifiers with several stages can be used.
A voltage divider with R1 is installed at the input. If the input voltage increases, at the base of transistor VT1 it also increases. At the same time, the current through transistor VT2 increases, which compensates for the increase in voltage, thereby maintaining it stable at the output.
Glass zener diodes and zener diodes in plastic cases are produced. In the first case, 2 numbers are applied to them, between which the letter V is located. The inscription 9V1 means that U st = 9.1 V.
The inscriptions on the plastic case are deciphered using a datasheet, where you can also find out other parameters.
The dark ring on the body indicates the cathode to which the plus is connected.
A zener diode is a diode with special properties. The advantage of zener diodes is a high level of voltage stabilization over a wide range of operating current changes, as well as simple connection diagrams. To stabilize the low voltage, the devices are turned on in the forward direction, and they begin to work like ordinary diodes.
READERS SUGGEST-
ANALOG ~ POWERFUL
To stabilize the load supply voltage, they often use the simplest parametric stabilizer (Fig. 1), in which power from the rectifier is supplied through a ballast resistor, and a zener diode is connected in parallel with the load.
Such a stabilizer is operational at load currents not exceeding the maximum stabilization current for a given stabilizer. And if the load current is significantly higher, they use a more powerful zener diode, for example, the D815 series, which allows a stabilization limit of 1... 1.4 A (D815A).
If such a zener diode is not available, a low-power one will do, but it must be used in conjunction with a powerful transistor, as shown in Fig. 2. The result is an analogue of a powerful zener diode, providing a fairly stable voltage across the load even at a current of 2 A, although the maximum stabilization current of the KS147A stabilizer indicated in the diagram is 58 mA.
The analogue works like this. As long as the supply voltage coming from the rectifier is less than the breakdown voltage of the zener diode, the transistor is closed, the current through the analogue is insignificant (the direct horizontal branch of the volt-ampere characteristic of the analogue shown in Fig. 3), as the supply voltage increases, the zener diode breaks through, current begins to flow through it and the transistor opens slightly (isog-
zener diode
nut part of the characteristic). A further increase in the supply voltage leads to a sharp increase in the current through the zener diode and transistor, and therefore to stabilization of the output voltage at a certain value (vertical branch of the characteristic), as in a conventional parametric stabilizer.
The stabilization effect is achieved due to the fact that in breakdown mode the zener diode has a low differential resistance and deep negative feedback is carried out from the collector of the transistor to its base. Therefore, as the output voltage decreases, the current through the zener diode and the base of the transistor will decrease, which will lead to a significantly greater (by several times) decrease
collector current, which means an increase in output voltage. When the output voltage increases, the reverse process will be observed -
The value of the stabilized output voltage is determined by summing the stabilization voltage of the zener diode with the voltage of the emitter junction of the open transistor (^0.7 V for a silicon transistor and 0.3 V for a germanium transistor). The maximum stabilization current of the analogue will be almost times higher than the same
parameter of the zener diode used. Accordingly, the power dissipation on the transistor will be the same number of times greater than the power on the zener diode.
From the above relationships it is easy to conclude that the static transmission coefficient of a powerful transistor must be no less than the quotient of the maximum current consumption of the load divided by the maximum stabilization current of the zener diode. The maximum permissible collector current of the transistor and the voltage between the collector and emitter must exceed the specified analogue stabilization current and output voltage, respectively.
When using a pnp structure transistor, it should be connected in accordance with the one shown in Fig. 4 scheme. In this embodiment, the transistor can be mounted directly on the chassis of the powered structure, and the remaining parts of the analogue can be mounted on the terminals of the transistor.
To reduce output voltage ripple and reduce the differential resistance of the analogue, an oxide capacitor with a capacity of 100.. 500 μF can be connected in parallel to the zener diode terminals.
In conclusion, a little about the temperature voltage coefficient (TCV) of the analogue. When using precision zener diodes of the D818, KS191 series, the TKN analogue will be significantly worse than the TKN zener diode. If a zener diode with a stabilization voltage of more than 16 V is used, the TKN of the analogue will be approximately equal to the TKN of the zener diode, and with zener diodes D808 - D814 the TKN of the analogue will improve.
I. KURSKY
FROM THE EDITOR. The article by I. Kursky does not raise the question of choosing a ballast resistor, keeping in mind that you already have a parametric stabilizer circuit and you just need to select a powerful zener diode. If there is no such circuit, use the recommendations for calculating the ballast resistor given in the article by V. Krylov “Simple voltage stabilizer” in Radio, 1977, No. 9, p. 53, 54
Zener diodes (Zener diodes, Z-diodes) are designed to stabilize the voltage and operating modes of various components of electronic equipment. The operating principle of the zener diode is based on the phenomenon of Zener breakdown of the n-junction. This type of electrical breakdown occurs in reverse-biased semiconductor junctions when the voltage increases above a certain critical level. In addition to the Zener breakdown, avalanche breakdown is known and used to stabilize voltage. Typical dependences of the current through a semiconductor device (zener diode) on the magnitude of the applied forward or reverse voltage (volt-ampere characteristics, current-voltage characteristics) are shown in Fig. 1.1.
The forward branches of the current-voltage characteristics of different zener diodes are almost identical (Fig. 1.1), and the reverse branch has individual characteristics for each type of zener diode. These parameters: stabilization voltage; minimum and maximum stabilization current; the angle of inclination of the current-voltage characteristic, characterizing the value of the dynamic resistance of the zener diode (its “quality”);
maximum power dissipation; temperature coefficient of stabilization voltage (TKN) - used for circuit calculations.
A typical zener diode connection circuit is shown in Fig. 1.2. The value of the damping resistance R1 (in kOhm) is calculated by the formula:
To stabilize the AC voltage or symmetrically limit its amplitude at the UCT level, symmetrical zener diodes are used (Fig. 1.3), for example, type KS 175. Such zener diodes can be used to stabilize DC voltage, turning them on without observing polarity. You can get a “symmetrical” zener diode from two “asymmetrical” ones by connecting them back to back according to the circuit shown in Fig. 1.4.
Industrially produced semiconductor zener diodes allow you to stabilize voltage over a wide range: from 3.3 to 180 V. Thus, there are zener diodes that allow you to stabilize low voltages: 3.3; 3.9; 4.7; 5.6 V is KS133, KS139, KS147, KS156, etc. If it is necessary to obtain a non-standard stabilization voltage, for example, 6.6 V, you can connect two KS133 zener diodes in series. For three such zener diodes, the stabilization voltage will be 9.9 V. For a stabilization voltage of 8.0 V, you can use a combination of zener diodes KS133 and KS147 (i.e. 3.3 + 4.7 V) or a zener diode KS175 and a silicon diode (KD503) - in the forward direction (i.e. 7.5+0.5 V).
In situations where it is necessary to obtain a stable voltage of less than 2...3 V, stabistors are used - semiconductor diodes operating on the direct branch of the current-voltage characteristic (Fig. 1.1).
Note that instead of stabilizers, conventional germanium (Ge), silicon (Si), selenium (Se), gallium arsenide (GaAs) and other semiconductor diodes can be successfully used (Fig. 1.5). The stabilization voltage, depending on the current flowing through the diode, will be: for germanium diodes - 0.15...0.3 b; for silicon - 0.5...0.7 V.
Particularly interesting is the use of light-emitting diodes for voltage stabilization (Fig. 1.6) [R 11/83-40].
LEDs can perform two functions simultaneously: by their glow, indicate the presence of voltage and stabilize its value at the level of 1.5...2.2 V. The stabilization voltage of UCT LEDs can be determined by the approximate formula: L/Cr=1236/L. (B), where X is the wavelength of the LED radiation in nm [Рл 4/98-32].
To stabilize the voltage, the reverse branch of the current-voltage characteristic of semiconductor devices (diodes and transistors), which are not specifically intended for these purposes, can be used (Fig. 1.7, 1.8, and also Fig. 20.7). This voltage (avalanche breakdown voltage) usually exceeds 7 V and is not highly repeatable even for semiconductor devices of the same type. To avoid thermal damage to semiconductor devices during such an unusual mode of operation, the current through them should not exceed fractions of a milliampere. Thus, for diodes D219, D220, the breakdown voltage (stabilization voltage) can be in the range from 120 to 180 V [P 9/74-62; R 10/76-46; R 12/89-65].
To stabilize low voltages, the circuits shown in Fig. are used. 1.9 - 1.12. The circuit (Fig. 1.9) [Goroshkov B.I.] uses a “diode” parallel connection of two silicon transistors. The stabilization voltage of this circuit is 0.65...0.7 V for silicon transistors and about 0.3 V for germanium transistors. The internal resistance of such a stabistor analogue does not exceed 5...10 Ohms with a stabilization coefficient of up to 1000...5000. However, when the ambient temperature changes, the instability of the circuit's output voltage is about 2 mV per degree.
In the diagram in Fig. 1.10 [R 6/69-60; VRYA 84-9] used sequential connection of germanium and silicon transistors. The load current of this analogue of a zener diode can be 0.02... 10 mA. The devices shown in Fig. 1.11 and 1.12 [Рл 1/94-33], use back-to-back connection of transistors of the p-p-p and p-p-p structures and differ only in that to increase the output voltage in one of the circuits, a silicon diode is connected between the bases of the transistors (one or several). The stabilization current of zener diode analogues (Fig. 1.11, 1.12) can be in the range of 0.1...100 mA, the differential resistance in the working section of the current-voltage characteristic does not exceed 15 Ohms.
Low voltages can also be stabilized using field-effect transistors (Fig. 1.13, 1.14). The stabilization coefficient of such circuits is very high: for a single-transistor circuit (Fig. 1.13) it reaches 300 at a supply voltage of 5... 15 V, for a two-transistor circuit (Fig. 1.14) under the same conditions it exceeds 1000 [P 10/95-55]. The internal resistance of these zener diode analogs is 30 Ohms and 5 Ohms, respectively.
A voltage stabilizer can be obtained using a dinistor analogue as a zener diode (Fig. 1.15, see also Chapter 2) [Goroshkov B.I.].
To stabilize voltages at high currents in the load, more complex circuits are used, shown in Fig. 1.16 - 1.18 [R 9/89-88, R 12/89-65]. To increase the load current, it is necessary to use powerful transistors installed on heat sinks.
A voltage stabilizer operating in a wide range of supply voltage variations (from 4.5 to 18 6), and having an output voltage value slightly different from the lower limit of the supply voltage, is shown in Fig. 1.19 [Goroshkov B.I.].
The types of zener diodes and their analogues discussed earlier do not allow smooth regulation of the stabilization voltage. To solve this problem, circuits of adjustable parallel stabilizers, similar to zener diodes, are used (Fig. 1.20, 1.21).
An analogue of a zener diode (Fig. 1.20) allows you to smoothly change the output voltage in the range from 2.1 to 20 V [R 9/86-32]. The dynamic resistance of such a “zener diode” at a load current of up to 5 mA is 20...50 Ohms. Temperature stability is low (-3x10"3 1/°C).
The low-voltage analogue of the zener diode (Fig. 1.21) allows you to set any output voltage in the range from 1.3 to 5 V. The stabilization voltage is determined by the ratio of resistors R1 and R2. The output resistance of such a parallel stabilizer at a voltage of 3.8 V is close to 1 Ohm. The output current is determined by the parameters of the output transistor and for KT315 it can reach 50... 100 mA.
Original circuits for obtaining a stable output voltage are shown in Fig. 1.22 and 1.23. The device (Fig. 1.22) is an analogue of a symmetrical zener diode [E 9/91]. For a low-voltage stabilizer (Fig. 1.23), the voltage stabilization factor is 10, the output current does not exceed 5 mA, and the output resistance varies from 1 to 20 Ohms.
An analogue of a low-voltage differential-type zener diode in Fig. 1.24 has increased stability [P 6/69-60]. Its output voltage depends little on temperature and is determined by the difference in the stabilization voltages of two zener diodes. The increased temperature stability is explained by the fact that when the temperature changes, the voltage on both zener diodes changes simultaneously and in close proportions.
Literature: Shustov M.A. Practical circuit design (Book 1), 2003
Stable salary, stable life, stable state. The last one is not about Russia, of course :-). If you look in an explanatory dictionary, you can clearly understand what “stability” is. On the first lines, Yandex immediately gave me the designation of this word: stable - this means constant, stable, not changing.
But most often this term is used in electronics and electrical engineering. In electronics, constant values of a parameter are very important. This can be current, voltage, signal frequency, etc. Deviation of the signal from any given parameter can lead to incorrect operation of the electronic equipment and even to its breakdown. Therefore, in electronics it is very important that everything works stably and does not fail.
In electronics and electrical engineering stabilize the voltage. The operation of electronic equipment depends on the voltage value. If it changes to a lesser extent, or even worse, to an increase, then the equipment in the first case may not work correctly, and in the second case it may even burst into flames.
In order to prevent voltage spikes and drops, various Surge Protectors. As you understand from the phrase, they are used to stabilize“playing” voltage.
The simplest voltage stabilizer in electronics is a radio element zener diode. Sometimes it is also called Zener diode. In the diagrams, zener diodes are designated something like this:
The terminal with a “cap” is called the same as that of a diode - cathode, and the other conclusion is anode.
Zener diodes look the same as diodes. In the photo below, on the left is a popular type of modern zener diode, and on the right is one of the samples from the Soviet Union
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If you take a closer look at the Soviet zener diode, you can see this schematic designation on it itself, indicating where its cathode is and where its anode is.
The most important parameter of a zener diode is, of course, stabilization voltage. What is this parameter?
Let's take a glass and fill it with water...
No matter how much water we pour into a glass, its excess will pour out of the glass. I think this is understandable to a preschooler.
Now by analogy with electronics. The glass is a zener diode. The water level in a glass full to the brim is stabilization voltage Zener diode. Imagine a large jug of water next to a glass. We will just fill our glass with water from the jug, but we don’t dare touch the jug. There is only one option - pour water from a jug by punching a hole in the jug itself. If the jug were smaller in height than the glass, then we would not be able to pour water into the glass. To explain it in electronics terms, the jug has a “voltage” greater than the “voltage” of the glass.
So, dear readers, the whole principle of operation of a zener diode is contained in the glass. No matter what stream we pour on it (well, of course, within reason, otherwise the glass will carry away and break), the glass will always be full. But it is necessary to pour from above. This means, The voltage we apply to the zener diode must be higher than the stabilization voltage of the zener diode.
In order to find out the stabilization voltage of the Soviet zener diode, we need a reference book. For example, in the photo below there is a Soviet zener diode D814V:
We look for parameters for it in online directories on the Internet. As you can see, its stabilization voltage at room temperature is approximately 10 Volts.
Foreign zener diodes are marked more easily. If you look closely, you can see a simple inscription:
.JPG)
5V1 - this means the stabilization voltage of this zener diode is 5.1 Volts. Much easier, right?
The cathode of foreign zener diodes is marked mainly with a black stripe
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How to check the zener diode? Yes, just like! You can see how to check the diode in this article. Let's check our zener diode. We set it to continuity and attach the red probe to the anode, and the black probe to the cathode. The multimeter should show a forward voltage drop.
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We swap the probes and see one. This means that our zener diode is in full combat readiness.
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Well, it's time for experiments. In the circuits, a zener diode is connected in series with a resistor:
Where Uin – input voltage, Uout.st. – output stabilized voltage
If we look closely at the diagram, we get nothing more than a voltage divider. Everything here is elementary and simple:
Uin=Uout.stab +Uresistor
Or in words: the input voltage is equal to the sum of the voltages on the zener diode and the resistor.
This scheme is called parametric stabilizer on one zener diode. The calculation of this stabilizer is beyond the scope of this article, but if anyone is interested, google it ;-)
So, let's put together the circuit. We took a resistor with a nominal value of 1.5 Kilohms and a zener diode with a stabilization voltage of 5.1 Volts. On the left we connect the Power Supply, and on the right we measure the resulting voltage with a multimeter:
.JPG)
Now we carefully monitor the readings of the multimeter and power supply:
.JPG)
So, while everything is clear, let’s add more tension... Oops! Our input voltage is 5.5 Volts, and our output voltage is 5.13 Volts! Since the stabilization voltage of the zener diode is 5.1 Volts, as we can see, it stabilizes perfectly.
.JPG)
Let's add some more volts. The input voltage is 9 Volts, and the zener diode is 5.17 Volts! Amazing!
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We also add... The input voltage is 20 Volts, and the output, as if nothing had happened, is 5.2 Volts! 0.1 Volt is a very small error, it can even be neglected in some cases.
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I think it wouldn’t hurt to consider the current-voltage characteristic (VAC) of the zener diode. It looks something like this:
Where
Ipr– forward current, A
Upr– forward voltage, V
These two parameters are not used in the zener diode
Uarr– reverse voltage, V
Ust– rated stabilization voltage, V
Ist– rated stabilization current, A
Nominal means a normal parameter at which long-term operation of the radio element is possible.
Imax– maximum zener diode current, A
Immin– minimum zener diode current, A
Ist, Imax, Imin – This is the current that flows through the zener diode when it operates.
Since the zener diode operates in reverse polarity, unlike a diode (the zener diode is connected with the cathode to the plus, and the diode with the cathode to the minus), then the working area will be exactly the one marked with the red rectangle.
As we see, at some voltage Urev our graph begins to fall down. At this time, such an interesting thing as a breakdown occurs in the zener diode. In short, it can no longer increase the voltage on itself, and at this time the current in the zener diode begins to increase. The most important thing is not to overdo the current, more than Imax, otherwise the zener diode will be damaged. The best operating mode of the zener diode is considered to be the mode in which the current through the zener diode is somewhere in the middle between its maximum and minimum values. This is what will appear on the graph operating point operating mode of the zener diode (marked with a red circle).
Previously, in times of scarce parts and the beginning of the heyday of electronics, a zener diode was often used, oddly enough, to stabilize the output voltage. In old Soviet books on electronics you can see this section of the circuit of various power supplies:
On the left, in the red frame, I marked a section of the power supply circuit that is familiar to you. Here we get DC voltage from AC voltage. On the right, in the green frame, is the stabilization diagram ;-).
Currently, three-terminal (integrated) voltage stabilizers are replacing stabilizers based on zener diodes, since they stabilize the voltage many times better and have good power dissipation.
On Ali you can immediately take a whole set of zener diodes, ranging from 3.3 Volts to 30 Volts. Choose to your taste and color.
Although during the preparation of the collection schemes were specially selected that use the most common, widely available and cheap elements, it would not be amiss to indicate the order of use of other elements that equally or with great success replace the missing ones.
When replacing one element with another, it is recommended to first use reference literature. In a brief appendix, even if one wishes, it is impossible to list all possible options for replacing elements, because there are more than a dozen names of semiconductor diodes alone. However, it is possible to give a general approach to the possible use of some device elements instead of others.
Let's start with semiconductor diodes. Conventionally, all semiconductor diodes used in the collection are divided into low-power high-frequency germanium diodes (diodes type D9B - D9Zh), low-power silicon pulse (high-frequency) - KD503A and silicon (low-frequency) - KD102A (B). The letter at the suffix (end) of the element designation (A, B, C, etc.) means a variant of the basic model, differing in some way from the rest.
In foreign publications, general-purpose diodes are often designated in a single way: these are universal low-frequency or high-frequency germanium or silicon diodes. Unless the design specifies special requirements for the diodes, the minimum requirements for them are:
High-frequency germanium or silicon diodes - with a maximum reverse voltage of at least 30 V (in relation to collection circuits - even 15 V), forward current of at least 10 mA. Operating frequency - not lower than several MHz.
High frequency germanium diodes: D9B - D9Zh; GD402 (1D402); GD507; GD508\GD511 and others.
Switching silicon diodes: KD503 (2D503); KD504\ KD509 - KD512] KD514; KD520 - KD522 and others.
Low-frequency (power) diodes - with a maximum reverse voltage of at least 300 V, forward current of at least 100 mA. Operating frequency - not lower than several kHz.
Silicon low-frequency diodes: KD102 - KD105\D226 and others with an operating voltage not lower than the voltage used in a specific circuit.
Of course, semiconductor devices that have higher performance and are often more expensive (designed for a higher operating current, a higher maximum frequency, a higher reverse voltage, etc.) can successfully replace the diode recommended in the collection, an outdated model diode.
When replacing zener diodes, first of all you should pay attention to the stabilization voltage. All collection circuits use predominantly low-power zener diodes. Currently, a wide range of different zener diodes are available, which are often interchangeable without any reservations. As already mentioned in one of the sections of the book, see Chapter 1, a zener diode for any increased or non-standard voltage can be composed of other zener diodes connected in series, or their combination with a chain of forward-biased germanium and (or) silicon diodes.
Issues of complete replacement of semiconductor devices are also discussed in Chapter 1.
When replacing transistors, you should be guided by the following. For these devices there is also a division into silicon, germanium, low-frequency, high-frequency, high-power, low-power transistors, etc.
This collection most often presents the most common transistors produced by industry for over 30 years, these are KT315 - silicon low-power high-frequency p-p-p structures. Their structural antonyms are KT361. Among the high-power silicon transistors, this is the KT805 p-p-p structure; germanium low-power high-frequency - GT311 (1T311) p-p-p and their antonyms p-p-p structure - GT313 (1T313). The main characteristics of these transistors are given above.
For all these transistors, of course, there is a large selection of equivalent and related redundant semiconductor devices, sometimes differing from the prototype only in name.
The main replacement criteria are as follows: maximum operating voltage at the transistor collector, maximum collector current, maximum power dissipated at the collector, maximum operating frequency, current transfer coefficient. Less often, for the circuits presented in the collection, the magnitude of the residual collector-emitter voltage and the noise characteristics of the transistor are significant.
When replacing one transistor with another, none of these parameters should be underestimated or worsened. At the same time, in comparison with rather ancient models of transistors, their modern varieties have automatically and evolutionarily absorbed properties that are obviously improved compared to their distant ancestors.
So, for example, transistors of the KT315 type can be replaced with more advanced transistors of the KT3102 type (low-noise high-frequency silicon transistors), KT645 (more powerful small-sized high-frequency transistors), etc., which have obviously better characteristics.
KT361 transistors can be replaced by transistors of the KT3107 type (low-noise high-frequency silicon transistors) or others similar.
Powerful transistors of the KT805 (2T805) type, used in collection circuits mainly in ULF output stages and voltage stabilizers, can be replaced without damage to the operation of the circuits by analogues, transistors of the KTVxx (2T8xx) series of the p-p-p structure, where xx is the serial number of the development . Exceptions to this series are transistors KT809, KT812, KT826, KT828, KT838, KT839, KT846, KT856, etc.
It should be noted that if during operation the transistor heats up noticeably, it means its operating mode is selected incorrectly, resistors of other ratings are used, or there is an installation error. If the operation of a transistor at an increased collector current is provided for by the operating conditions of a particular circuit, and the transistor heats up noticeably, you should think about replacing this element with a more powerful one or taking measures to cool it. Typically, a simple radiator or the use of a fan allows you to increase the permissible power dissipated by a semiconductor element (transistor or diode) by 10...15 times.
Sometimes one powerful semiconductor device (diode or transistor) can be replaced by low-power devices connected in parallel. However, when including this, the following must be taken into account. Since during the manufacture of semiconductor devices, even from the same batch of production, their properties differ noticeably, with a simple parallel connection, the load on them can be distributed extremely unevenly, which will cause sequential burnout of these devices. To uniformly distribute currents in parallel-connected diodes and transistors, it is difficult to include a resistor with a resistance of several to tens of Ohms in series with the diode or in the emitter circuit of the transistor.
If it is necessary to use a semiconductor diode designed for high voltage, replacement can be done by connecting several diodes of the same type, designed for low voltage, in series. As before, to ensure uniform distribution of the reverse voltage, which is the most dangerous for the operation of the diode assembly, a resistor with a resistance of several hundred kOhms to several megohms should be connected in parallel to each of the diodes of the assembly. Of course, similar connection schemes for transistors are also known, but they are rarely used. In any case, for the circuits presented in the collection, such replacements will not be required, since all circuits are designed primarily for low-voltage power supply.
When replacing field-effect transistors, the situation is much more complicated. Although field-effect transistors themselves appeared on the pages of magazines and books quite a long time ago, their range is not so representative, and the spread of parameters is more pronounced. Replacing foreign-made field-effect transistors can be especially difficult. As for the circuits of the collection, as was said earlier, it uses only the most accessible elements, including field-effect transistors.
In the diagrams presented on the pages of the collection, we repeatedly encounter the use of telephone capsules for a somewhat unusual purpose - simultaneously as low-frequency oscillating circuits and sound emitters. Basically, standard and widely used products are used as such telephone capsules. This is a telephone capsule of the TK-67 type, used in domestically produced telephone sets, and an earphone of the TM-2 (TM-4) type, usually used in devices for the hearing impaired. Of course, these telephone capsules can be replaced by other domestic or foreign ones that have similar properties, however, in some cases, it may be necessary to select the capacitor capacitance (for example, if this telephone capsule has a low-frequency resonant oscillatory circuit).
