Circuits on the transistor p210. Voltage stabilizer on P210. Checking the components and assembling the power supply
The stabilized power supply discussed below is one of the first devices that are assembled by novice radio amateurs. This is a very simple but very useful device. For its assembly, expensive components are not needed, which are quite easy to pick up for a beginner, depending on the required characteristics of the power supply.
The material will also be useful to those who wish to understand in more detail the purpose and calculation of the simplest radio components. In particular, you will learn in detail about such components of the power supply as:
- power transformer;
- diode bridge;
- smoothing capacitor;
- zener diode;
- resistor for zener diode;
- transistor;
- load resistor;
- LED and resistor for it.
Typical scheme of a stabilized power supply
There are a lot of various power supply circuits with voltage stabilization today. But one of the simplest configurations that a beginner should start with is built on just two key components - a zener diode and a powerful transistor. Naturally, there are other details in the circuit, but they are auxiliary.Circuits in radio electronics are usually disassembled in the direction in which current flows through them. In a voltage stabilized power supply, everything starts with a transformer (TR1). It performs several functions at once. First, the transformer lowers the mains voltage. Secondly, it ensures the operation of the circuit. Thirdly, it powers the device that is connected to the unit.
Diode bridge (BR1) - designed to rectify low mains voltage. In other words, an alternating voltage enters it, and the output is already constant. Without a diode bridge, neither the power supply itself nor the devices that will be connected to it will work.
A smoothing electrolytic capacitor (C1) is needed in order to remove the ripples present in the household network. In practice, they create interference that adversely affects the operation of electrical appliances. If, for example, we take a sound amplifier powered by a power supply without a smoothing capacitor, then these very ripples will be clearly audible in the speakers in the form of extraneous noise. In other devices, interference can cause incorrect operation, malfunctions, and other problems.
The zener diode (D1) is a component of the power supply that stabilizes the voltage level. The fact is that the transformer will produce the desired 12 V (for example) only when there is exactly 230 V in the power outlet. However, in practice, such conditions do not exist. Voltage can both sink and rise. The same transformer will give at the output. Due to its properties, the zener diode equalizes the low voltage, regardless of the surges in the network. For the correct operation of this component, a current-limiting resistor (R1) is needed. It is discussed in more detail below.
Transistor (Q1) - needed to amplify the current. The fact is that the zener diode is not able to pass through itself the entire current consumed by the device. Moreover, it will work correctly only in a certain range, for example, from 5 to 20 mA. This is frankly not enough to power any devices. A powerful transistor copes with this problem, the opening and closing of which is controlled by a zener diode.
Smoothing capacitor (C2) - designed for the same as the above C1. In typical circuits of stabilized power supplies, there is also a load resistor (R2). It is needed so that the circuit remains operational when nothing is connected to the output terminals.
Other components may be present in such schemes. This is a fuse that is placed in front of the transformer, and an LED signaling that the unit is turned on, and additional smoothing capacitors, and another amplifying transistor, and a switch. All of them complicate the circuit, however, increase the functionality of the device.
Calculation and selection of radio components for a simple power supply
The transformer is selected according to two main criteria - the voltage of the secondary winding and the power. There are other parameters, but within the framework of the material they are not particularly important. If you need a power supply, say, 12 V, then the transformer must be selected so that a little more can be removed from its secondary winding. With power, everything is the same - we take it with a small margin.The main parameter of the diode bridge is the maximum current that it can pass. It is this characteristic that should be targeted in the first place. Consider examples. The unit will be used to power a device that consumes a current of 1 A. This means that the diode bridge needs to be taken at about 1.5 A. Let's say you plan to power any 12-volt device with a power of 30 watts. This means that the current consumption will be about 2.5 A. Accordingly, the diode bridge must be at least 3 A. Its other characteristics (maximum voltage, etc.) can be neglected within such a simple circuit.
In addition, it is worth saying that you can not take a diode bridge ready-made, but assemble it from four diodes. In this case, each of them must be rated for the current passing through the circuit.
To calculate the capacitance of a smoothing capacitor, rather complex formulas are used, which in this case are useless. Usually a capacitance of 1000-2200 uF is taken, and this will be quite enough for a simple power supply. You can take a larger capacitor, but this will significantly increase the cost of the product. Another important parameter is the maximum voltage. According to it, the capacitor is selected depending on what voltage will be present in the circuit.
It should be borne in mind here that in the segment between the diode bridge and the zener diode, after turning on the smoothing capacitor, the voltage will be approximately 30% higher than at the transformer terminals. That is, if you make a 12 V power supply, and the transformer outputs with a margin of 15 V, then in this section, due to the operation of the smoothing capacitor, it will be approximately 19.5 V. Accordingly, it must be designed for this voltage (the closest standard rating 25 V).
The second smoothing capacitor in the circuit (C2) is usually taken with a small capacitance - from 100 to 470 microfarads. The voltage in this section of the circuit will already be stabilized, for example, to a level of 12 V. Accordingly, the capacitor must be designed for this (the closest standard rating is 16 V).
But what if the capacitors of the required ratings are not available, and you are reluctant to go to the store (or there is simply no desire to buy them)? In this case, it is quite possible to use the parallel connection of several smaller capacitors. It should be taken into account that the maximum operating voltage will not be summed up with such a connection!
The zener diode is selected depending on what voltage we need to get at the output of the power supply. If there is no suitable denomination, then several pieces can be connected in series. The stabilized voltage, in this case, will be summed up. For example, let's take a situation where we need to get 12 V, and there are only two 6 V zener diodes available. By connecting them in series, we will get the desired voltage. It is worth noting that in order to obtain an average rating, connecting two zener diodes in parallel will not work.
It is possible to choose the most accurate current-limiting resistor for a zener diode only experimentally. To do this, a resistor with a nominal value of approximately 1 kOhm is included in an already working circuit (for example, on a breadboard), and an ammeter and a variable resistor are placed between it and the zener diode in the open circuit. After turning on the circuit, you need to rotate the knob of the variable resistor until the required rated stabilization current flows through the circuit section (indicated in the characteristics of the zener diode).
The amplifying transistor is selected according to two main criteria. Firstly, for the circuit under consideration, it must necessarily be an n-p-n structure. Secondly, in the characteristics of the existing transistor, you need to look at the maximum collector current. It should be slightly more than the maximum current for which the assembled power supply will be designed.
The load resistor in typical circuits is taken from 1 kOhm to 10 kOhm. You should not take a smaller resistance, because if the power supply is not loaded, too much current will flow through this resistor and it will burn out.
Design and manufacture of printed circuit board
Now let's briefly consider a good example of the development and assembly of a stabilized power supply with our own hands. First of all, you need to find all the components present in the circuit. If there are no capacitors, resistors or zener diodes of the required ratings, we get out of the situation in the ways described above.
Next, you will need to design and manufacture a printed circuit board for our device. For beginners, it is best to use simple and, most importantly, free software for this, such as Sprint Layout.
We place all the components on the virtual board according to the selected scheme. We optimize their location, adjust depending on what specific parts are available. At this stage, it is recommended to double-check the actual dimensions of the components and compare them with those added to the developed circuit. Pay special attention to the polarity of electrolytic capacitors, the location of the terminals of the transistor, zener diode and diode bridge.
If you go to add a signal LED to the power supply, then it can be included in the circuit both before the zener diode and after (preferably). To select a current-limiting resistor for it, you must perform the following calculation. From the voltage of the circuit section, we subtract the voltage drop across the LED and divide the result by the rated current of its supply. Example. In the area to which we plan to connect the signal LED, there is a stabilized 12 V. The voltage drop for standard LEDs is about 3 V, and the rated supply current is 20 mA (0.02 A). We get that the resistance of the current-limiting resistor is R=450 Ohm.
Checking the components and assembling the power supply
After developing the board in the program, we transfer it to fiberglass, etch, tin the tracks and remove excess flux.Resistors are checked with an ohmmeter. The zener diode should "ring" in only one direction. We check the diode bridge according to the scheme. The diodes built into it should only conduct current in one direction. To test capacitors, you will need a special device for measuring electrical capacitance. In an npn transistor, current must flow from the base to the emitter and to the collector. It should not flow in other directions.
It is best to start assembling with small parts - resistors, a zener diode, an LED. Then the capacitors are soldered, the diode bridge.
Pay special attention to the process of installing a powerful transistor. If you confuse his conclusions, the scheme will not work. In addition, this component will get quite hot under load, so it must be installed on a radiator.
The last to install is the largest part - the transformer. Next, a network plug with a wire is soldered to the terminals of its primary winding. Wires are also provided at the output of the power supply.
It remains only to thoroughly double-check the correctness of the installation of all components, wash off the flux residues and turn on the power supply to the network. If everything is done correctly, the LED will glow, and the multimeter will show the desired voltage at the output.
The power supply circuit with a stabilizer on the P210 transistor is shown in Figure 1. At one time, this was a very popular circuit. It could be found in various modifications, both in industrial equipment and in amateur radio.
The whole circuit is mounted directly on the radiator using support posts and hard transistor outputs. The radiator area at a load current of six amperes should be about 500 cm². Since the collectors of transistors VT1 and VT2 are connected, their cases do not need to be isolated from each other, but it is better to isolate the radiator from the case (if it is metal). Diodes D1 and D2 - any 10A. The area of radiators for diodes is ≈ 80 cm². Approximately calculate the heat sink area for different semiconductor devices, so to speak, to estimate, you can use the diagram given in the article. I usually use U-shaped radiators bent from a strip of 3 mm aluminum (see photo 1). 
Strip size 120×35mm. Transformer Tr1 - rewound transformer from the TV. For example, TS-180 or similar. The diameter of the wire of the secondary winding is 1.25 ÷ 1.5 mm. The number of turns of the secondary winding will depend on the transformer you use. How to calculate the transformer can be found in the article, heading - "Independent calculations". Each of the windings III and IV must be designed for a voltage of 16V. By replacing the trimming resistor R4 with a variable one and adding an ammeter to the circuit, it will be possible to charge car batteries with this power supply.
The proposed power supply is made on transistors. It has a relatively simple circuit (Fig. 1), and the following parameters:
output voltage................................................ .................................... 3...30 V;
stabilization coefficient when the mains voltage changes from 200 to 240 V ......... 500;
maximum load current ............................................................... .................................... 2 A;
temperature instability .............................................................. ...................... 10 mV/°C;
pulsation amplitude at I max .............................................. ............................... 2 mV;
output impedance .................................................................. ................................. 0.05 ohm.
The main rectifier is assembled on diodes VD5-VD8, the voltage from which is supplied to the filter capacitor C2 and the regulating composite transistor VT2, VT4-VT6, connected according to the common collector circuit.
On transistors VT3, VT7, a feedback signal amplifier is made. Transistor VT7 is powered by the output voltage of the power supply. Resistor R9 is its load. The emitter voltage of the transistor VT7 is stabilized by the Zener diode VD17. As a result, the current of this transistor depends only on the base voltage, which can be changed by changing the voltage drop across the resistor R10 of the voltage divider R10, R12-R21. Any increase or decrease in the base current of the transistor VT7 leads to an increase or decrease in the collector current of the transistor VT3. In this case, the regulating element is locked or unlocked to a greater extent, respectively, reducing or increasing the output voltage of the power supply. By switching the resistors R13-R21 with the SA2.2 section of the SA2 switch, the output voltage of the unit is changed in steps of 3 V. The output voltage is smoothly regulated within each step using the resistor R12.
The auxiliary parametric stabilizer on the VD9 zener diode and the R1 resistor serves to power the VT3 transistor, the supply voltage of which is equal to the sum of the output voltage of the unit and the stabilization voltage of the VD9 zener diode. Resistor R3 is the load of transistor VT3.
Capacitor C4 eliminates self-excitation at high frequencies, capacitor C5 reduces the output voltage ripple. Diodes VD16, VD15 accelerate the discharge of the capacitor C6 and the capacitive load connected to the unit when the output voltage is set to a lower level.
On the transistor VT1, trinistor VS1 and relay K1, an overload protection device is made for the power supply. As soon as the voltage drop across the resistor R5, proportional to the load current, exceeds the voltage across the diode VD12, the transistor VT1 opens. Following it, the trinistor VS1 opens, shunting the base of the regulating transistor through the VD14 diode, and the current through the regulating element of the stabilizer is limited. At the same time, relay K1 is activated, with contacts K1.2 connecting the base of the regulating transistor to a common wire. Now the output current of the stabilizer is determined only by the leakage current of transistors VT2, VT4-VT6. Contacts K1.1 relay K1 turns on the bulb H2 "Overload". To return the stabilizer to its original mode, you need to turn it off for a few seconds and turn it on again. To eliminate the surge at the output of the unit when it is turned on, as well as to prevent the protection from tripping with a significant capacitive load, capacitor C3, resistor R2 and diode VD11 are used. When the power supply is turned on, the capacitor is charged in two circuits: through the resistor R2 and through the resistor R3 and the VD11 diode. In this case, the voltage on the base of the regulating transistor slowly increases following the voltage on the capacitor C3 until the stabilization voltage is established. Then the diode VD11 closes and the capacitor C3 continues to charge through the resistor R2. Diode VD11, closing, excludes the influence of the capacitor on the operation of the stabilizer. Diode VD10 is used to accelerate the discharge of capacitor C3 when the power supply is turned off.
All elements of the power supply, except for the power transformer, powerful control transistors, switches SA1-SA3, fuse holders FU1, FU2, light bulbs H1, H2, pointer meter, output connectors and a smooth output voltage regulator, are placed on printed circuit boards.
The location of the power supply units inside the case can be seen from Fig.4. The P210A transistors are mounted on a pin radiator mounted at the rear of the case and having an effective dissipation area of about 600 cm2. Ventilation holes with a diameter of 8 mm are drilled in the bottom of the case at the place where the radiator is attached. The housing cover is fixed in such a way that an air gap of about 0.5 cm wide is maintained between it and the radiator. For better cooling of the control transistors, it is recommended to drill ventilation holes in the cover.
A power transformer is fixed in the center of the case, and next to it, on the right side, a P214A transistor is fixed on a 5x2.5 cm duralumin plate. The plate is insulated from the body with insulating bushings. The diodes KD202V of the main rectifier are mounted on duralumin plates screwed to the printed circuit board. The board is installed above the power transformer with the parts down.
The power transformer is made on a toroidal tape magnetic circuit OL 50-80/50. The primary winding contains 960 turns of wire PEV-2 0.51. Windings II and IV have output voltages of 32 and 6 V, respectively, with a voltage on the primary winding of 220 V. They contain 140 and 27 turns of wire PEV-2 0.31. Winding III is wound with PEV-2 1.2 wire and contains 10 sections: the lower one (according to the diagram) - 60, and the rest 11 turns each. The output voltages of the sections are respectively equal to 14 and 2.5 V. The power transformer can also be wound on another magnetic circuit, for example, on a rod from TVs UNT 47/59 and others. The primary winding of such a transformer is retained, and the secondary windings are rewound to obtain the above voltages.
In power supplies, instead of P210A transistors, transistors of the P216, P217, P4, GT806 series can be used. Instead of P214A transistors, any of the P213-P215 series. MP26B transistors can be replaced with any of the MP25, MP26 series, and P307V transistors with any of the P307 - P309, KT605 series. Diodes D223A can be replaced by diodes D223B, KD103A, KD105; KD202V diodes - any powerful diodes with a permissible current of at least 2 A. Instead of the D818A zener diode, you can use any other zener diode from this series. Instead of the trinistor KU101B, any of the KU101, KU102 series will do. As relay K1, a small-sized relay of the RES-9 type was used, passports: RS4.524.200, RS4.524.201, RS4.524.209, RS4.524.213.
The relays of these passports are designed for an operating voltage of 24 ... 27 V, but they begin to operate already at a voltage of 15 ... 16 V. When an overload of the power supply occurs (see Fig. 2), as already noted, the trinistor VS1 is unlocked, which limits stabilizer current to a small value. At the same time, the filter capacitor of the main rectifier (C2) is immediately recharged to approximately the amplitude value of the alternating voltage (with the lower position of the SA2.1 switch, this voltage is at least 20 V) and conditions are created for fast and reliable operation of the relay.
Switches SA2 - small-sized biscuit type 11P3NPM. In the second block, the contacts of the two sections of this switch are paralleled and are used to switch sections of the power transformer. When the power supply is on, the position of the switch SA2 should be changed at load currents not exceeding 0.2 ... turning it off. Variable resistors for smooth adjustment of the output voltage should be selected with the dependence of the resistance on the angle of rotation of the engine type “A” and preferably wire. Miniature incandescent bulbs HCM-9 V-60 mA are used as signal lamps H1, H2.
Any pointer device can be used for a current of full deflection of the pointer up to 1 mA and a front part size of not more than 60X60 mm. In this case, it must be remembered that the inclusion of a shunt in the output circuit of the power supply increases its output impedance. The greater the current of the total deviation of the arrow of the device, the greater the resistance of the shunt (provided that the internal resistances of the devices are of the same order). To prevent the influence of the device on the output impedance of the power supply, the switch SA3 during operation should be set to measure voltage (upper position according to the diagram). In this case, the shunt of the device closes and is excluded from the output circuit.
The adjustment comes down to checking the correctness of the installation, selecting the resistors of the control stages to adjust the output voltage within the required limits, setting the protection operation current and selecting the resistances of the resistors Rsh and Rd for the pointer meter. Before tuning, a short wire jumper is soldered instead of a shunt.
When setting up the power supply, switch SA2 and the slider of resistor R12 are set to the position corresponding to the minimum output voltage (lower position according to the diagram). By selecting the resistor R21, a voltage of 2.7 ... 3 V is achieved at the output of the block. Then the slider of the resistor R12 is moved to the extreme right position (upper according to the diagram) and by selecting the resistor R10 the voltage at the output of the block is set to 6 - 6.5 V. Next move switch SA2 one position to the right and select resistor R20 so that the output voltage of the unit increases by 3 V. And so in order, each time switching switch SA2 one position to the right, resistors R19-R13 are selected until the final voltage is established at the output of the power supply 30 V. Resistor R12 for smooth adjustment of the output voltage, you can take a different value: from 300 to 680 ohms, however, approximately proportionally you need to change the resistance of resistors R10, R13-R20.
The protection operation is configured by selecting the resistor R5.
The additional resistor Rd and the shunt Rsh are selected by comparing the readings of the PA1 meter with the readings of an external measuring device. In this case, the external device must be as accurate as possible. As an additional resistor, you can use one or two series-connected resistors OMLT, MT for a dissipation power of at least 0.5 W. When selecting the resistor Rd, switch SA3 is switched to the “Voltage” position and a voltage of 30 V is set at the output of the power supply. An external device, not forgetting to switch it to measuring voltages, is connected to the output of the unit.
Simple power supply 1. V 2. 0AAjout. 2. 01. Subscribe to our Vkontakte group - http: //vk. Facebook - https: //www. A simple but powerful fixed voltage power supply can be built using the L7 linear regulator.
SD1. 13, having a maximum collector current of 3. A. A microcircuit stabilizer with the participation of two parallel transistors makes it possible to obtain a stabilized voltage of 1.
V with an output current of 2. A and more, depending on the parameters of the power transformer.
The circuit has short circuit protection. The protection current is determined by the voltage divider in the base of the KT8 transistor. After the protection is triggered or when the power source is turned on, it is necessary to press the button to bring the stabilizer into operation. In the event of a protection operation, the output voltage will drop to 1. V, the KT8 transistor will close.
CT8. 16, further, a microcircuit stabilizer and two powerful transistors. The output voltage will drop, and will be held in this state for a long time. The power of the power supply depends on the parameters of the power transformer, power filter, and the number of power transistors installed on the corresponding heat sink.
Transistors P210 - germanium, powerful low-frequency, structures - p-n-p. To power such a radio station from on-board batteries, a special power supply is required, which includes a voltage converter.
A simple but powerful enough power supply with protection current is determined by the voltage divider in the base of the KT817 transistor and.
- Voltage stabilizer P210, I want to understand how the principle of robots. P210 is just a transistor (in my opinion germanium), powerful.
- Scheme of the power supply, power supply, switching. The proposed scheme of a simple (only 3 transistors) power supply is beneficial.
- In the event of a short circuit at the output of the power supply, the emitter of the transistor VT1 will be connected to the anode of the diode VD5, and to it.
- Replacing transistors in a laboratory PSU. Charger based on PC power supplies. BP is free from it.
- Transistors P210 - germanium, powerful low-frequency, structures - p-n-p.
- A charger on a p210 transistor can be repaired without much effort, a power supply circuit with a p210 transistor.
Typical mistakes in the design of germanium amplifiers come from the desire to get a wide bandwidth, low distortion, etc. from the amplifier.
Here is a diagram of my first germanium amplifier, designed by me in 2000.
Although the circuit is quite functional, its sound quality leaves much to be desired.
Practice has shown that the use of differential cascades, current generators, cascades with a dynamic load, current mirrors and other tricks with environmental protection do not always lead to the desired result, and sometimes they simply lead to a dead end.
The best practical results for obtaining high sound quality, gives the use of single-cycle cascades before. amplification and the use of inter-stage matching transformers.
Presented to your attention is a germanium amplifier with an output power of 60 W, at a load of 8 ohms. Output transistors used in the P210A, P210Sh amplifier. Linearity 20-16000Hz.
There is practically no subjective lack of high frequencies.
With a load of 4 ohms, the amplifier produces 100 watts.
Amplifier circuit on P-210 transistors.
The amplifier is powered by an unstabilized power supply with an output, bipolar voltage of +40 and -40 volts.
For each channel, a separate bridge of D305 diodes is used, which are installed on small radiators.
Filter capacitors, it is desirable to use at least 10000 microns per shoulder.
Power transformer data:
- iron 40 to 80. The primary winding contains 410 vit. wires 0.68. Secondary 59 vit. wires 1.25, wound four times (two windings - the upper and lower arms of one amplifier channel, the remaining two - the second channel)
.Additionally for power transformer:
iron w 40 to 80 from the power supply of the KVN TV. After the primary winding, a copper foil screen is installed. One open loop. A pin is soldered to it, which is then grounded.
You can use any iron that is suitable for the cross section w.
The matching transformer is made on iron Sh20 by 40.
The primary winding is divided into two parts and contains 480 vit.
The secondary winding contains 72 turns and is wound in two wires at the same time.
First, 240 vit primary is wound, then secondary, then again 240 vit primary.
Primary wire diameter 0.355 mm, secondary 0.63 mm.
The transformer is assembled in a joint, the gap is a cable paper gasket of approximately 0.25 mm.
A 120 ohm resistor is included to ensure no self-excitation when the load is off.
Chains of 250 Ohm +2 to 4.7 Ohm are used to supply the initial bias to the bases of the output transistors.
With the help of 4.7 ohm trimmers, the quiescent current is set to 100mA. At the resistors in the emitters of the output transistors of 0.47 ohms, there should be a voltage of 47 mV.
The output transistors P210, at the same time, should be almost barely warm.
To accurately set the zero potential, the 250 ohm resistors must be precisely matched (in a real design they consist of four 1 kOhm 2 W resistors).
For a smooth setting of the quiescent current, trimming resistors R18, R19 of the SP5-3V type 4.7 Ohm 5% are used.
The appearance of the amplifier from the back is shown in the photo below.
Can you find out your impressions of the sound of this version of the amplifier, in comparison with the previous transformerless version on P213-217?
Even more saturated juicy sounding. I will especially emphasize the quality of the bass. Listening was carried out with open acoustics on the speakers 2A12.
- Jean, but why exactly P215 and P210, and not GT806/813, are in the scheme?
Carefully look at the parameters and characteristics of all these transistors, I think you will understand everything, and the question will disappear by itself.
I clearly understand the desire of many to make the germanium amplifier more broadband. But the reality is that for audio purposes, many high-frequency germanium transistors are not quite suitable. From domestic ones, I can recommend P201, P202, P203, P4, 1T403, GT402, GT404, GT703, GT705, P213-P217, P208, P210. The bandwidth expansion method is the use of common base circuits, or the use of imported transistors.
The use of circuits with transformers made it possible to achieve excellent results on silicon. An amplifier based on 2N3055 has been developed.
I will share soon.
- And what about the "0" at the output? At a current of 100 mA, it is hard to believe that it will be possible to keep it in the process of operation in an acceptable + -0.1 V.
In similar schemes 30 years ago (Grigoriev's scheme), this is solved either by a "virtual" midpoint or by an electrolyte:
Grigoriev amplifier.
Zero potential is held within the limit you specify. The quiescent current is quite possible to do and 50mA. It is controlled by an oscilloscope until the step disappears. No more need. Further, all op-amps easily work on a 2k load. Therefore, there are no special problems of matching with CD.
Some high-frequency germanium transistors require attention and further study in audio circuits. 1T901A, 1T906A, 1T905A, P605-P608, 1TS609, 1T321. Try it, gain experience.
Sometimes there were sudden failures of transistors 1T806, 1T813, so I can recommend them with caution.
They need to set "fast" current protection, designed for a current greater than the maximum in this circuit. So that there is no protection operation in normal mode. Then they work very reliably.
I will add my version of Grigoriev's scheme
Version of the Grigoriev amplifier circuit.
By selecting a resistor from the base of the input transistor, half of the supply voltage is set at the connection point of the 10 ohm resistors. By selecting a resistor in parallel with the 1N4148 diode, the quiescent current is set.
- 1. In my reference books D305 are normalized to 50v. Maybe it's safer to use D304? I think 5A is enough.
- 2. Specify the real h21 for devices installed in this layout or their minimum required values.
You are absolutely right. If there is no need for high power. The voltage across each diode is about 30V, so there are no reliability issues. Transistors with the following parameters were used; P210 h21-40, P215 h21-100, GT402G h21-200.
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