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Rectifier diodes reference book. Pulse rectifier diodes. Device and design features

The main purpose of rectifier diodes is voltage conversion. But this is not the only area of application for these semiconductor elements. They are installed in switching and control circuits, used in cascade generators, etc. Beginning radio amateurs will be interested in learning how these semiconductor elements are structured, as well as their operating principle. Let's start with the general characteristics.

Device and design features

The main structural element is a semiconductor. This is a wafer of silicon or germanium crystal, which has two regions of p and n conductivity. Because of this design feature, it is called planar.

When manufacturing a semiconductor, the crystal is processed as follows: to obtain a p-type surface, it is treated with molten phosphorus, and for a p-type surface, it is treated with boron, indium or aluminum. During heat treatment, diffusion of these materials and the crystal occurs. As a result, a region with a p-n junction is formed between two surfaces with different electrical conductivities. The semiconductor obtained in this way is installed in the housing. This protects the crystal from external influences and promotes heat dissipation.

Designations:

A – cathode output.
B – crystal holder (welded to the body).
C – n-type crystal.
D – p-type crystal.
E – wire leading to the anode terminal.
F – insulator.
G – body.
H – anode output.

As already mentioned, as r-n basics transitions using silicon or germanium crystals. The former are used much more often, this is due to the fact that in germanium elements the reverse currents are much higher, which significantly limits the permissible reverse voltage (it does not exceed 400 V). While for silicon semiconductors this characteristic can reach up to 1500 V.

In addition, germanium elements have a much narrower operating temperature range, it varies from -60°C to 85°C. When the upper temperature threshold is exceeded, the reverse current sharply increases, which negatively affects the efficiency of the device. For silicon semiconductors, the upper threshold is about 125°C-150°C.

Power classification

The power of the elements is determined by the maximum permissible direct current. In accordance with this characteristic, the following classification has been adopted:

List of main characteristics

Below is a table describing the main parameters of rectifier diodes. These characteristics can be obtained from the datasheet (technical description of the element). As a rule, most radio amateurs turn to this information in cases where the element indicated in the diagram is not available, which requires finding a suitable analogue for it.

Note that in most cases, if you need to find an analogue of a particular diode, the first five parameters from the table will be quite sufficient. In this case, it is advisable to take into account the operating temperature range of the element and frequency.

Principle of operation

The easiest way to explain the principle of operation of rectifier diodes is with an example. To do this, we simulate the circuit of a simple half-wave rectifier (see 1 in Fig. 6), in which power comes from an alternating current source with voltage U IN (graph 2) and goes through VD to the load R.

Rice. 6. Operating principle of a single-diode rectifier

During the positive half-cycle, the diode is in the open position and passes current through it to the load. When the turn of the negative half-cycle comes, the device is locked and no power is supplied to the load. That is, there is a kind of cutting off of the negative half-wave (in fact, this is not entirely true, since when this process There is always a reverse current, its magnitude is determined by the characteristic I arr).

As a result, as can be seen from graph (3), at the output we receive pulses consisting of positive half-cycles, that is, D.C.. This is the principle of operation of rectifying semiconductor elements.

Note that the pulse voltage at the output of such a rectifier is only suitable for powering low-noise loads, an example would be Charger for flashlight acid battery. In practice, this scheme is used only by Chinese manufacturers in order to reduce the cost of their products as much as possible. Actually, the simplicity of the design is its only pole.

The disadvantages of a single-diode rectifier include:

Low level of efficiency, since negative half-cycles are cut off, the efficiency of the device does not exceed 50%.
The output voltage is approximately half that of the input.
High noise level, which manifests itself in the form of a characteristic hum at the frequency of the supply network. Its reason is asymmetrical demagnetization of the step-down transformer (in fact, this is why for such circuits it is better to use a damping capacitor, which also has its negative sides).

Note that these disadvantages can be somewhat reduced; to do this, it is enough to make a simple filter based on a high-capacity electrolyte (1 in Fig. 7).

Rice. 7. Even a simple filter can significantly reduce ripple

The operating principle of such a filter is quite simple. The electrolyte is charged during the positive half-cycle and discharged when the negative half-cycle occurs. The capacitance must be sufficient to maintain the voltage across the load. In this case, the pulses will be somewhat smoothed out, approximately as shown in graph (2).

The above solution will improve the situation somewhat, but not much; if you power, for example, active computer speakers from such a half-wave rectifier, a characteristic background will be heard in them. To fix the problem, a more radical solution will be required, namely a diode bridge. Let's look at the operating principle of this circuit.

Design and principle of operation of a diode bridge

The significant difference between such a circuit (from a half-wave circuit) is that voltage is supplied to the load in each half-cycle. The circuit diagram for connecting semiconductor rectifier elements is shown below.

As can be seen from the above figure, the circuit uses four semiconductor rectifier elements, which are connected in such a way that only two of them operate during each half-cycle. Let us describe in detail how the process occurs:

The circuit receives an alternating voltage Uin (2 in Fig. 8). During the positive half-cycle, the following circuit is formed: VD4 – R – VD2. Accordingly, VD1 and VD3 are in the locked position.
When the sequence of the negative half-cycle occurs, due to the fact that the polarity changes, a circuit is formed: VD1 – R – VD3. At this time, VD4 and VD2 are locked.
The next period the cycle repeats.

As can be seen from the result (graph 3), both half-cycles are involved in the process and no matter how the input voltage changes, it flows through the load in one direction. This principle of operation of a rectifier is called full-wave. Its advantages are obvious, we list them:

Since both half-cycles are involved in the work, the efficiency increases significantly (almost twice).
Ripple at the output of the bridge circuit also doubles the frequency (compared to a half-wave solution).
As can be seen from graph (3), the level of dips decreases between pulses, so it will be much easier for the filter to smooth them out.
The voltage at the rectifier output is approximately the same as at the input.

Interference from the bridge circuit is negligible, and becomes even less when using a filter electrolytic capacitance. Thanks to this, this solution can be used in power supplies for almost any amateur radio design, including those that use sensitive electronics.

Note that it is not at all necessary to use four rectifier semiconductor elements; it is enough to take a ready-made assembly in a plastic case.

This case has four pins, two for the input and the same number for the output. The legs to which AC voltage is connected are marked with a “~” sign or the letters “AC”. At the output, the positive leg is marked with the symbol “+”, respectively, the negative leg is marked with “-”.

On a schematic diagram, such an assembly is usually denoted in the form of a rhombus, with a graphic display of a diode located inside.

The question of whether it is better to use an assembly or individual diodes cannot be answered unambiguously. There is no difference in functionality between them. But the assembly is more compact. On the other hand, if it fails, only a complete replacement will help. If in this case individual elements are used, it is enough to replace the failed rectifier diode.

Although all diodes are rectifiers, the term is usually applied to devices intended to supply power, to distinguish them from elements used for small signal circuits. The high power rectifier diode is used to rectify AC current with low supply frequency of 50Hz when high power is emitted during load.

Diode characteristics

The main task of the diode is conversion of alternating voltage to direct voltage through use in rectifier bridges. This allows electricity to flow in only one direction, keeping the power supply running.

The operating principle of a rectifier diode is not difficult to understand. Its element consists of a structure called a pn junction. The p-type side is called the anode and the n-type side is called the cathode. Current is passed from the anode to the cathode, while flowing in the opposite direction is almost completely prevented. This phenomenon is called straightening. It converts alternating current into unidirectional current. This type of device can handle higher electricity than regular diodes, which is why they are called high power. The ability to conduct high amounts of current can be classified as their main feature.

Today Silicon diodes are most often used. When compared to elements made from germanium, they have a larger connection surface. Because germanium has low resistance to heat, most semiconductors are made from silicon. Devices made from germanium have a significantly lower permissible reverse voltage and junction temperature. The only advantage that a germanium diode has over silicon is the lower voltage value when operating in forward bias (VF (IO) = 0.3 ÷ 0.5 V for germanium and 0.7 ÷ 1.4 V for silicon) .

Types and technical parameters of rectifiers

Today there are many different types of straighteners. They are usually classified according to:

The most common types are 1 A, 1.5 A, 3 A, 5 A and 6 A. There are also standard devices with a maximum average rectified current of up to 400 A. Forward voltage can vary from 1.1 mV to 1.3 kV.

characterized by the following permissible limits:

An example of a high performance element is the 2x30A Dual High Current Rectifier Diode, which is best suited for base stations, welders, AC/DC power supplies and industrial applications.

Application value

As the simplest semiconductor component, this type of diode has a wide range of applications in modern electronic systems. Various electronic and electrical circuits use this component as an important device to obtain the required result. The scope of application of rectifier bridges and diodes is extensive. Here are a few such examples:

turning alternating current into direct voltage;
isolation of signals from the power supply;
voltage reference;
signal size control;
mixing signals;
detection signals;
lighting systems;
lasers.

Power rectifier diodes are a vital component of power supplies. They are used to regulate power in computers and cars, and can also be used in battery chargers and computer power supplies.

In addition, they are often used for other purposes (for example, in the detector of radio receivers for radio modulation). The Schottky barrier diode variant is especially valued in digital electronics. The operating temperature range from -40 to +175 °C allows these devices to be used under any conditions.

Device and design features

The main structural element is a semiconductor. This is a wafer of silicon or germanium crystal, which has two regions of p and n conductivity. Because of this design feature, it is called planar.

Designations:

A – cathode output.
B – crystal holder (welded to the body).
C – n-type crystal.
D – p-type crystal.
E – wire leading to the anode terminal.
F – insulator.
G – body.
H – anode output.

As already mentioned, silicon or germanium crystals are used as the basis for the p-n junction. The former are used much more often, this is due to the fact that in germanium elements the reverse currents are much higher, which significantly limits the permissible reverse voltage (it does not exceed 400 V). While for silicon semiconductors this characteristic can reach up to 1500 V.

Power classification

The power of the elements is determined by the maximum permissible direct current. In accordance with this characteristic, the following classification has been adopted:

List of main characteristics

Principle of operation

Rice. 6. Operating principle of a single-diode rectifier

During the positive half-cycle, the diode is in the open position and passes current through it to the load. When the turn of the negative half-cycle comes, the device is locked and no power is supplied to the load. That is, there is a kind of cutting off of the negative half-wave (in fact, this is not entirely true, since during this process there is always a reverse current, its value is determined by the I arr. characteristic).

As a result, as can be seen from graph (3), at the output we receive pulses consisting of positive half-cycles, that is, direct current. This is the principle of operation of rectifying semiconductor elements.

Note that the pulse voltage at the output of such a rectifier is only suitable for powering low-noise loads, an example would be a charger for a flashlight acid battery. In practice, this scheme is used only by Chinese manufacturers in order to reduce the cost of their products as much as possible. Actually, the simplicity of the design is its only pole.

The disadvantages of a single-diode rectifier include:

Low level of efficiency, since negative half-cycles are cut off, the efficiency of the device does not exceed 50%.
The output voltage is approximately half that of the input.
High noise level, which manifests itself in the form of a characteristic hum at the frequency of the supply network. Its reason is asymmetrical demagnetization of the step-down transformer (in fact, this is why for such circuits it is better to use a damping capacitor, which also has its negative sides).

Note that these disadvantages can be somewhat reduced; to do this, it is enough to make a simple filter based on a high-capacity electrolyte (1 in Fig. 7).

Rice. 7. Even a simple filter can significantly reduce ripple

Design and principle of operation of a diode bridge

The circuit receives an alternating voltage Uin (2 in Fig. 8). During the positive half-cycle, the following circuit is formed: VD4 – R – VD2. Accordingly, VD1 and VD3 are in the locked position.
When the sequence of the negative half-cycle occurs, due to the fact that the polarity changes, a circuit is formed: VD1 – R – VD3. At this time, VD4 and VD2 are locked.
The next period the cycle repeats.

Since both half-cycles are involved in the work, the efficiency increases significantly (almost twice).
Ripple at the output of the bridge circuit also doubles the frequency (compared to a half-wave solution).
As can be seen from graph (3), the level of dips decreases between pulses, so it will be much easier for the filter to smooth them out.
The voltage at the rectifier output is approximately the same as at the input.

Note that it is not at all necessary to use four rectifier semiconductor elements; it is enough to take a ready-made assembly in a plastic case.

On a schematic diagram, such an assembly is usually denoted in the form of a rhombus, with a graphic display of a diode located inside.

All these components differ in purpose, materials used, types р-n transitions, design, power and other features and characteristics. Rectifier, pulse diodes, varicaps, Schottky diodes, SCRs, LEDs, and thyristors are widely used. Let's consider their main specifications and general properties, although each type of these semiconductor components has many of its own purely individual parameters.

These are electronic devices with one p-n junction that have one-way conductivity and are designed to convert alternating voltage to direct voltage. The frequency of the rectified voltage is usually no more than 20 kHz. Rectifier diodes also include Schottky diodes.

The main parameters of low-power rectifier diodes at normal temperatures are given in table 1 medium power rectifier diodes in table 2 and high power rectifier diodes in table 3

A type of rectifier diodes are . These devices on the reverse branch of the current-voltage characteristic have an avalanche characteristic similar to zener diodes. The presence of an avalanche characteristic allows them to be used as circuit protection elements against surge voltages, including directly in rectifier circuits.

In the latter case, rectifiers based on these diodes operate reliably under conditions of switching overvoltages that occur in inductive circuits when the power supply or load is turned on and off. Basic parameters of avalanche diodes at normal temperature environment shown in

To rectify voltages above several kilovolts, rectifier columns have been developed, which are a set of rectifier diodes connected in series and assembled into a single structure with two terminals. These devices are characterized by the same parameters as rectifier diodes. The main parameters of rectifying columns at normal ambient temperatures are given in

To reduce the overall dimensions of rectifiers and ease their installation, they are produced rectifier blocks(assemblies) having two, four or more diodes, electrically independent or connected in the form of a bridge and assembled in one housing. The main parameters of rectifier blocks and assemblies at normal ambient temperature are given in

Pulse diodes They differ from rectifiers in their short reverse recovery time or large pulse current. Diodes of this group can be used in rectifiers at high frequencies, for example, as a detector or modulators, converters, pulse shapers, limiters and other pulse devices, see reference tables 7 And 8

Tunnel diodes perform the functions of active elements (devices capable of amplifying the signal power) electronic circuits amplifiers, generators, switches mainly in microwave ranges. Tunnel diodes have high operating speed, small overall dimensions and weight, are resistant to radiation, operate reliably in a wide temperature range, and are energy efficient

The main parameters of tunnel and reverse diodes at normal ambient temperatures are given in

- their principle of operation is based on the electrical (avalanche or tunnel) breakdown of the p-n junction, during which a sharp increase in the reverse current occurs, and the reverse voltage changes very little. This property is used to stabilize voltage in electrical circuits. Due to the fact that avalanche breakdown is characteristic of diodes made on the basis of a semiconductor with a large band gap, the starting material for zener diodes is silicon. In addition, silicon has low thermal current and stable characteristics over a wide temperature range. To operate in zener diodes, a flat section of the I-V characteristic of the reverse current is used, within which sharp changes in the reverse current are accompanied by very small changes in the reverse voltage.

Parameters of zener diodes and stabistors low power are given in , zener diodes and high power zener diodes - in , precision zener diodes -

Parameters of voltage limiters are given in

Varicaps reference book

These are semiconductor diodes with electrically controlled barrier junction capacitance. The change in capacitance is achieved by changing the reverse voltage. As with other diodes, the base resistance of the varicap should be small. At the same time, to increase the value of the breakdown voltage, a high resistivity of the base layers adjacent to the junction is desirable. Based on this, the main part of the base - the substrate - is low-resistance, and the base layer adjacent to the transition is high-resistance. Varicaps are characterized by the following main parameters. The total capacitance of the varicap SB is a capacitance that includes the barrier capacitance and the housing capacitance, i.e., the capacitance measured between the terminals of the varicap at a given (nominal) reverse voltage.

Light-emitting diode is a semiconductor device that converts electric current directly into light radiation. It consists of one or more crystals placed in a housing with contact leads and an optical system (lens) that generates the light flux. The crystal emission wavelength (color) depends on

These are the same LEDs only emitting light in the IR range

This is the simplest semiconductor laser, the basis of its design is typical p-n transition. The operating principle of the laser device is based on the fact that after free charge carriers are injected into the element p-n zone- transition, a population inversion is formed.

A semiconductor voltage limiter is a diode that operates on the reverse branch of the current-voltage characteristic with avalanche breakdown. It is used for protective purposes against overvoltage in circuits of integrated and hybrid circuits, radio-electronic elements, etc. Using voltage limiters, you can protect the input and output circuits of various electronic components from the effects of short-term overvoltages.

The information in the directory is presented in the format of original PDF files, and for ease of downloading is divided into collections in accordance with the English alphabet

Domestic diodes reference book

The reference book gives general information about domestic semiconductor diodes, namely, rectifiers, diode matrices, zener diodes and stabistors, varicaps, radiating and ultra-high semiconductor devices. It also tells about their classification and system of symbols. Conventional graphic designations are given in accordance with GOST 2.730-73, and terms and letter designations of parameters in accordance with GOST 25529-82. Some information is given about the use of voltage limiters and rules for installing diodes. The appendix contains dimensional drawings of the housings and an alphanumeric index for navigation.

This database is nothing more than an electronic reference book on semiconductor devices, including bridges and assemblies, and many radio components too.

The directory contains more than 65,000 radioelements. There is information from all leading manufacturers as of December 2016. The directory contains the following functions:

Sorting by several characteristics in any order of the directory
filtering for almost all characteristics
editing directory data
viewing documentation and drawing of the radio element housing
reference viewing of data sheets in PDF format

The following conventions are used in the reference tables:

U rev.max.	-	maximum permissible constant reverse voltage of the diode;
U rev.i.max.	-	maximum permissible pulse reverse voltage of the diode;
I pr.max.	-	maximum average forward current for the period;
I pr.i.max.	-	maximum pulse forward current per period;
I prg.	-	rectifier diode overload current;
f max.	-	maximum permissible diode switching frequency;
f slave	-	operating frequency of diode switching;
U pr at I pr	-	constant forward voltage of the diode at current I pr;
I arr.	-	constant reverse diode current;
Tk.max.	-	maximum permissible temperature of the diode body.
Tp.max.	-	maximum permissible diode junction temperature.

Semiconductor diodes are called single-junction (with one electrical junction) electrical converting devices with two external current leads. The electrical junction can be an electron-hole junction, a metal-semiconductor contact, or a heterojunction. The figure schematically shows the device of a diode with an electron-hole junction 1, separating the p-m n-regions (2 and 3) with different types of electrical conductivity.

The crystal 3 is equipped with external current leads 4 and placed in a metal, glass, ceramic or plastic housing 5, which protects the semiconductor from external influences (atmospheric, mechanical, etc.). Typically, semiconductor diodes have asymmetrical electron-hole junctions. One region of the semiconductor (with a higher concentration of impurities) serves as the emitter, and the other (with a lower concentration) serves as the base. At direct connection external voltage to the diode, the injection of minority charge carriers mainly occurs from the heavily doped region of the emitter to the lightly doped region of the base.

The amount of minority carriers passing in the opposite direction is significantly less than the injection from the emitter. Depending on the ratio of the linear dimensions of the junction and the characteristic length, planar and point diodes are distinguished. A diode is considered planar if its linear dimensions, which determine the junction area, are significantly larger than the characteristic length.

The characteristic length in the reference book for diodes is the smaller of two values - the thickness of the base and the diffusion length of minority carriers in the base. They determine the properties and characteristics of diodes. Point diodes include diodes with linear junction dimensions smaller than the characteristic length. A transition at the interface between regions with different types of conductivity has the properties of current rectification (one-way conduction); nonlinearity of the current-voltage characteristic; the phenomenon of charge carrier tunneling through a potential barrier under both reverse and forward bias; the phenomenon of impact ionization of semiconductor atoms at relatively high transition voltages; barrier capacitance, etc. These transition properties are used to create various types of semiconductor diodes.

Based on the frequency range in which diodes can operate, they are divided into low-frequency (LF) and high-frequency (HF). According to their purpose, LF diodes are divided into rectifier, stabilizing, pulse, and HF diodes - into detector, mixing, modular, parametric, switching, etc. Sometimes diodes that differ in basic physical processes are divided into a special group: tunnel, avalanche-flight, photo -, LEDs, etc.

Based on the material of the main semiconductor crystal, germanium, silicon, gallium arsenide and other diodes are distinguished. To designate semiconductor diodes in the directory, a six and seven-digit alphanumeric code is used (for example, KD215A, 2DS523G).

The first element - a letter (for widely used devices) or a number (for devices used in a special-purpose device) - indicates the material on which the device is made: G or 1 - germanium; K or 2 - silicon and its compounds; A or 3 - gallium compounds (for example, gallium arsenide); And or 4 - indium compounds (for example, indium phosphide).

The second element is a letter indicating a subclass or group of devices: D - rectifier, pulse diodes; C - rectifying posts and blocks; B - varicaps; And - pulse tunnel diodes; A - microwave diodes; C - zener diodes.

The third element - a number - determines one of the main features characterizing the device (for example, its purpose or principle of operation).

The fourth, fifth and sixth elements are a three-digit number indicating the serial number of the development of the technological type of the device.

The seventh element - the letter - conditionally determines the classification according to the parameters of devices manufactured using a single technology. Designation example: 2DS523G - a set of silicon pulse devices for special-purpose devices with a reverse resistance settling time from 150 to 500 ns; development number 23, group G. Development devices before 1973 in reference books. have three and four element notation systems.

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