What kind of transistor is needed for a sound amplifier. Circuits of transistor audio amplifiers
After mastering the basics of electronics, the novice radio amateur is ready to solder his first electronic designs. Power amplifiers audio frequency, as a rule, the most repeatable designs. There are quite a lot of schemes, each with its own parameters and design. This article will discuss several simple and fully working amplifier circuits that can be successfully repeated by any radio amateur. The article does not use complex terms and calculations; everything is simplified as much as possible so that no additional questions arise.
Let's start with a more powerful circuit.
So, the first circuit is made on the well-known TDA2003 microcircuit. This is a mono amplifier with an output power of up to 7 watts into a 4 ohm load. I want to say that the standard circuit for connecting this microcircuit contains a small number of components, but a couple of years ago I came up with a different circuit on this microcircuit. In this circuit, the number of components is reduced to a minimum, but the amplifier has not lost its sound parameters. After developing this circuit, I began making all my amplifiers for low-power speakers using this circuit.
The circuit of the presented amplifier has a wide range of reproducible frequencies, a supply voltage range from 4.5 to 18 volts (typical 12-14 volts). The microcircuit is installed on a small heat sink, since the maximum power reaches up to 10 Watts.
The microcircuit is capable of operating at a load of 2 ohms, which means that 2 heads with a resistance of 4 ohms can be connected to the amplifier output.
The input capacitor can be replaced with any other one, with a capacity from 0.01 to 4.7 μF (preferably from 0.1 to 0.47 μF), you can use both film and ceramic capacitors. It is advisable not to replace all other components.
Volume control from 10 to 47 kOhm.
The output power of the microcircuit allows it to be used in low-power speakers for PCs. It is very convenient to use the chip for stand-alone speakers for a mobile phone, etc.
The amplifier works immediately after switching on and does not require additional adjustment. It is recommended to additionally connect the power supply minus to the heat sink. It is advisable to use all electrolytic capacitors at 25 Volts.
The second circuit is assembled using low-power transistors and is more suitable as a headphone amplifier.
This is probably the highest quality circuit of its kind, the sound is clear, you can feel the entire frequency spectrum. With good headphones, it feels like you have a full-fledged subwoofer.
The amplifier is assembled with only 3 reverse conduction transistors; as the cheapest option, transistors of the KT315 series were used, but their choice is quite wide.
The amplifier can operate at a low-impedance load, up to 4 ohms, which makes it possible to use the circuit to amplify the signal of a player, radio, etc. A 9-volt Krona battery is used as a power source.
The final stage also uses KT315 transistors. To increase the output power, you can use KT815 transistors, but then you will have to increase the supply voltage to 12 volts. In this case, the amplifier power will reach up to 1 Watt. The output capacitor can have a capacity from 220 to 2200 µF.
The transistors in this circuit do not heat up, therefore, no cooling is needed. If you use larger output transistors, you may need small heat sinks for each transistor.
And finally - the third scheme. An equally simple, but proven version of the amplifier structure is presented. The amplifier is capable of operating from undervoltage up to 5 volts, in this case the output power of the PA will be no more than 0.5 W, and the maximum power with a 12 volt power supply reaches up to 2 Watts.
The output stage of the amplifier is built on a domestic complementary pair. The amplifier is regulated by selecting resistor R2. To do this, it is advisable to use a 1 kOhm trimmer. Slowly rotate the regulator until the quiescent current of the output stage is 2-5 mA.
The amplifier does not have high input sensitivity, so it is advisable to use a pre-amplifier before the input.
The diode plays a significant role in the circuit; it is here to stabilize the mode of the output stage.
The output stage transistors can be replaced with any complementary pair of corresponding parameters, for example KT816/817. The amplifier can power low-power stand-alone speakers with a load resistance of 6-8 ohms.
Today it is no longer considered fashionable to solder various shiny parts on a homemade circuit board, as it was twenty years ago. However, in our cities there are still amateur radio circles, and specialized magazines are published in offline and online modes.
Why has interest in radio electronics dropped sharply? The fact is that in modern stores everything that is required is sold, and there is no longer any need to study something or look for ways to acquire it.
But not everything is as simple as we would like. There are excellent speakers with active amplifiers and subwoofers on sale, wonderful imported stereo systems and multi-channel mixers with a wide range of capabilities, but low-power amplifiers are completely absent. As a rule, they are used to connect instruments at home, so as not to destroy the psyche of neighbors. It’s quite expensive to buy a device as part of a powerful device; the rational solution would be the following: put in a little effort and create homemade amplifier without outside help. Fortunately, today this is possible, and the Internet will be happy to help with this.
Amplifier "assembled on the knee" 
Attitude towards yourself assembled devices today is somewhat negative, and the expression “collect on your knees” is overly negative. But let’s not listen to the envious people, but let’s immediately turn to the first stage. 
First you need to select a scheme. Homemade type ULF can be made using transistors or a microcircuit. The first option is highly not recommended for beginning radio amateurs, as it will clutter the board and make repairing the device more difficult. It is best to replace a dozen transistors with one monolithic chip. This homemade amplifier will please the eye, it will be compact, and it will take a little time to assemble.
Today, the most popular and reliable chip is the TDA2005 type. It is already a two-channel ULF in itself; you just need to organize the power supply and supply the input and output signals. Such a simple homemade amplifier will cost no more than a hundred rubles, along with other parts and wires.
The output power of the TDA2005 ranges from 2 to 6 watts. This is enough to listen to music at home. The list of parts used, their parameters and, in fact, the diagram itself is shown below.
When the device is assembled, it is recommended to screw a small aluminum screen to the chip. This way, when heated, the heat will be better dissipated.
This homemade amplifier is powered by 12 volts. To implement it, purchase a small power supply or electrical adapter with the ability to switch output voltage values. The device current is no more than 2 amperes.
You can connect speakers with a power of up to 100 watts to such a ULF amplifier. The amplifier input can be supplied with a signal from mobile phone, DVD player or computer. At the output, the signal is received through a standard headphone jack.
Thus, we figured out how to assemble an amplifier in a short time for little money. A rational decision by practical people!
Amateur radio amplifier unit
Basic specifications power amplifier:
Rated output power, W, ........................2x25 (2x60)
Power band, kHz.................................................... 0.02 ...150(100)
Nominal input voltage, V.................................... 1(1)
Harmonic coefficient, %, at frequency, kHz:
1 .............................................................................. 0,1(0,1)
2 ............................................................................ 0,14(0,55)
10 ............................................................................ 0,2(0,9)
20 ............................................................................. 0,35(1,58)
Intermodulation distortion coefficient, %,......... 0.3(0.47)
Input impedance, kOhm................................................... .150
Quiescent current of the output stage, mA............................................. 50(50 )
The signal voltage amplification stage is made on op-amp A1. As can be seen from the diagram, part of the output signal is supplied to its power supply circuit through the circuit R6C3C4R4R5 (together with the zener diodes V6, V7, the elements of this circuit, except for the resistor R6, provide stabilization and filtering of the supply voltages). As a result, the voltages at the power terminals of the op-amp at the maximum signal are shifted (relative to the common wire) in the corresponding direction and the range of the output signal of the op-amp increases significantly. The large common-mode signals that arise at the inputs of the op-amp do not pose a danger, since the op-amp suppresses them well (typical value of the attenuation coefficient is 70...90 dB). When applying a signal to the inverting input, the stabilized supply voltages should not exceed +-28 V, on inverting inputs - a value equal to (11in + 28 V), where 11in is the amplitude of the input signal. In any case, the unused input must be connected to the common wire. The K140UD8A op-amp in power amplifiers can be replaced with K140UD8B, K140UD6, K140UD10, K140UD11, K544UD1. The worst results are obtained by using the K140UD7 OU. It is not at all recommended to use OU K140UD1B, K140UD2A, K140UD2B, K153UD1. Instead of KS518A zener diodes, you can use D814A, D814B zener diodes connected in series with a total stabilization voltage of about 18V.
High quality ULF
The amplifier described below is suitable for amplifying powerful audio signals as part of high-end audio reproduction installations, as well as for use as a powerful wideband operational amplifier.
Main technical characteristics of the amplifier:
Rated output power, W, with load resistance,
Ohm: 8................................................... ...........................................48
4..........................................................................................60
Reproducible frequency range with frequency response unevenness of no more than 0.5 dB and output power of 2 W, Hz...................10...200000
THD at rated power
in the range 20...20000 Hz, %.................................... ............0.05
Rated input voltage, V................................... 0.8
Input impedance, kOhm................................................... .......47
Output impedance, Ohm................................................... ....0.02
The input stage of the amplifier consists of two differential amplifiers (connected in parallel), made on transistors VT1, VT3 and VT2, VT4 of opposite structure. Current generators on transistors VT5, VT6 ensure stability of the values (about 1 mA) of the total emitter currents of differential pairs, as well as decoupling of power circuits. The signal to the output amplifier is supplied from controlled current generators (VT7, VT7), which operate in antiphase. This inclusion doubled the drive current, reduced nonlinear distortion and improved the frequency properties of the amplifier as a whole. Each of the arms of the symmetrical output amplifier is made according to the Darlington circuit, and is a three-stage amplifier (in two stages the transistors are connected according to a circuit with a common emitter and in one - with a common collector). The amplifier is covered by a frequency-dependent feedback loop, which determines its voltage transfer coefficient, which in the audio range is close to three. Since the signal feedback, taken from resistor R39 (R40), is proportional to changes in the current of the output transistor, then in addition a rather strict stabilization of the operating point of this transistor is carried out. The bias voltage of the output stage is determined by the resistance of the collector-emitter junction of transistor VT9 and is regulated by resistor R24. The bias voltage is thermally stabilized by a VD4 diode, which is mounted on the heat sink of one of the powerful transistors.
Correction elements R16, C4, C6 - C11 ensure the stability of the amplifier and level its frequency response. Passive filter low frequencies R2C1 prevents RF signals from entering the input. Chain C12R45L1R47 compensates for the reactive component of the load resistance. A unit for protecting output transistors from overcurrent and voltage overloads is assembled on transistors VT12 and VT13. Resistor R1 allows, if necessary, to limit the output power in accordance with the signal level from the preamplifier and the capabilities of the speaker used.
The amplifier can also use other low-power high-frequency silicon transistors, for example KT342A, KT342B and KT313B, KT315 and KT361 (with indices from B to E). Transistors VT14 and VT15 (possible replacement - KT816V, KT816G and KT817V, KT817G or KT626V and KT904A) are equipped with finned heat sinks measuring 23x25x12 mm. As output transistors, you can use KT818GM and KT819GM transistors, which allow you to receive powers of over 70 W when the supply voltage is increased. Zener diode VD1 can also be D816G or 2S536A, VD2 and VD3 - KS147A (with appropriate correction of the resistances of resistors R11 and R14).
AF power amplifier
Rated (maximum) power, W.................... 60(80)
Nominal frequency range, Hz................................ 20...20000
Harmonic coefficient in the nominal frequency range, % 0.03
Nominal input voltage, V...................................0.775
Output resistance, Ohm, no more.................................... 0.08
Output voltage slew rate, V/µs....... 40
The main voltage gain is provided by a cascade based on high-speed op-amp DA1. The pre-terminal stage of the amplifier is assembled using transistors VT1 - VT4. Unlike the prototype, the described amplifier has an output emitter follower made on transistors VT5, VT6 operating in mode “B”. Temperature stability is achieved by including relatively higher resistance resistors R19, R20 in the collector circuits of transistors VT3, VT4. Each arm of the pre-terminal stage is covered by a local feedback loop with a depth of at least 20 dB. The OOS voltage is removed from the collector loads of transistors VT3, VT4 and through dividers R11R14 and R12R15 is supplied to the emitter circuits of transistors VT1, VT2. Frequency correction and stability in the OOS circuit is provided by capacitors SYU, C11. Resistors R13, R16 and R19, R20 limit the maximum currents of the pre-final and final stages of the amplifier during a short circuit of the load. For any overload, the maximum current of transistors VT5, VT6 does not exceed 3.5...4 A, and in this case they do not overheat, since fuses FU1 and FU2 have time to burn and turn off the power to the amplifier.
The reduction in harmonic distortion was achieved by introducing a deep (at least 70 dB) general feedback loop, the voltage of which is removed from the output of the amplifier and fed through the divider C3C5R3R4 to the inverting input of the op-amp DA1. Capacitor C5 adjusts the frequency response of the amplifier through the OOS circuit. The R1C1 circuit connected at the amplifier input limits its bandwidth to 160 kHz. The maximum possible linearization of the frequency response frequency in the range of 10...200 Hz was achieved by appropriate selection of the capacitance of capacitors C1, SZ, C4.
Instead of those indicated in the diagram, you can use op-amps K574UD1A, K574UD1V and transistors of the same types as in the diagram, but with the indices G, D (VT1, VT2) and B (VT3 - VT6).
UMZCH with output stage on field-effect transistors
Main technical characteristics:
Nominal (maximum) output power, W. 45(65)
Harmonic coefficient, %, no more,.................................... 0.01
Nominal input voltage, mV................................. 775
Nominal frequency range, Hz, ......................... 20...100000
Output voltage slew rate, V/µs, ................60
Signal-to-noise ratio, dB.................................................... ......... 100
The input stage of the amplifier is made using op-amp DA1. To increase the amplitude of the output voltage, the UMZCH output transistors are controlled via the op-amp power circuits. The output signal is taken from the positive power supply terminal DA1 and, through the transistor VT1 connected according to the OB circuit, is supplied to one of the inputs of the differential cascade on transistors VT2, VT4. Its second input receives a stabilized voltage from a divider formed by diodes VD2 - VD5 and resistor R13.
The described amplifier does not require any special measures to protect the output transistors from short circuits in the load, since the maximum voltage between source and gate is only twice the same voltage in quiescent mode and corresponds to a current through the output transistor of approximately 9 A. This current the transistors used reliably withstand the time required to blow the fuses and disconnect the UMZCH from the power source.
Coil L1 is wound in one layer on a toroidal frame with an outer diameter of 20, an inner diameter of 10 and a height of 10 mm and contains 28 turns of PEV-2 1.0 wire.
In UMZCH it is advisable to use the KR544UD2A op amp, as the most broadband domestic op amp with internal frequency correction. Transistors KT3108A are interchangeable with KT313A, KT313B, and KP912B with KP912A and KP913, KP920A. 
High quality power amplifier
When designing the amplifier described below, the Kvod-405 amplifier was taken as a basis, successfully combining high technical characteristics and circuit simplicity. Structural scheme The amplifier mainly remained unchanged, only devices for protecting the transistors of the output stage from overload were excluded. Practice has shown that devices of this kind do not completely eliminate transistor failures, but often introduce nonlinear distortions at maximum output power. The transistor current can be limited in other ways, for example, by using overcurrent protection in voltage stabilizers. At the same time, it seems advisable to protect loudspeakers in the event of failure of the amplifier or power supplies. To improve the symmetry of the amplifier, the output stage is made on a complementary pair of transistors, and to reduce nonlinear step-type distortions, diodes VD5, VD6 are included between the bases of transistors VT9, VT10. This ensures fairly reliable closing of the output stage transistors in the absence of a signal. Slightly modified input circuit. The non-inverting input of op-amp DA1 was used as a signal signal, which made it possible to increase the input resistance of the amplifier (it is determined by the resistance of resistor R1 and is equal to 100 kOhm.) It should be noted, however, that even in the non-inverting version, the stability of the amplifier remains high. To prevent clicking in the speakers due to power-on transients, and to protect the speakers from DC voltage When the amplifier or power supplies fail, a simple, well-proven device (VT6 - VT8) is used, used in the industrial amplifier "Brig - 001". When this device is triggered, one of the lamps HL1, HL2 lights up, signaling the presence of a DC voltage of one polarity or another at the output of the amplifier. Basically, the circuit of the described amplifier does not differ from the circuit of the “Kvod -405” amplifier. The coils are wound with PEV-2 1.0 wire on frames with a diameter of 10 mm and contain: L1 and L3 - 50 turns each (inductance - 5...7 μH), L2 - 30 turns (3 μH).
Instead of those indicated in the diagram, the amplifier can use op-amps K574UD1B, K574UD1V, K544UD2, and also (with some deterioration in the parameters) K544UD1 and K140UD8A - K140UD8V; transistors KT312V, KT373A(VT2), KT3107B, KT3107I, KT313B, KT361V, KT361K (VT1, VT3, VT4), KT315V (VT6, VT8), KT801A, KT801B (VT7). Each of the KT825G transistors can be replaced with composite transistors KT814V, KT814G+KT818V, KT818G, and KT827A with composite transistors KT815V, KT815G+KT819V, KT819G. Diodes VD3 - VD6, VD11, VD12 - any silicon with a maximum forward current of at least 100 mA, VD7 - VD10 - the same, but with maximum current not less than 50 mA. In the absence of KS515A zener diodes, it is permissible to use D814A, D814B or KS175A zener diodes connected in series.
Maximum output power, W, into a 4 Ohm load..... 2x70
Nominal input voltage, V.................................... 0.2
Upper limit of the frequency range, kHz.................................... 50
Output voltage slew rate, V/µs......5.5
Signal-to-noise ratio (unweighted), dB.................................... 80
Harmonic coefficient, %, no more, ..............................................0, 05
Amplifier with multi-loop feedback
Main technical characteristics:
Nominal frequency range, Hz, .................................... 20...20000
Nominal load resistance, Ohm.................................... 4
Nominal (maximum) output. power, W, with load resistance, Ohm:
4 .................................................................................. 70(100)
8 ........................................................................................40(60)
Frequency range, Hz, ................................................... ........ 5...100000
Output voltage rise rate, V/µs, no less... 15 Harmonic coefficient, %, no more, at frequency, Hz:
20...5000 .................................................................................. 0,001
10000 ................................................................................ 0,003
20000 ................................................................................. 0,01
Harmonic coefficient, %, no more, ....................................... 0.01
Rated input voltage, V.................................................... 1
Input impedance, kOhm, min..................................................... 47
The first stage is assembled on an operational amplifier (op-amp) DA1, the rest - on transistors (the second and third - on VT1, VT3, respectively, the fourth - on VT8, VT11 and VT10, VT12, the fifth - on VT13, VT14). In the fourth (pre-final) stage, transistors of different structures are used, connected according to a composite emitter follower circuit, which made it possible to introduce local feedback into it and thus increase linearity and reduce output resistance. To reduce transient distortion at high frequencies, the output stage operates in AB mode, and the resistance of the bias circuit resistors (R30, R33) is limited to 15 Ohms. All transistor stages of the amplifier are covered by a local feedback loop with a depth of at least 50 dB. The OOS voltage is removed from the output of the amplifier and fed through the divider R10R12 into the emitter circuit of transistor VT1. Frequency correction and stability in the OOS circuit are provided by capacitor C4. The introduction of local OOS made it possible, even with the most unfavorable combinations of amplification properties of transistors, to limit the harmonic coefficient of this part of the amplifier to 0.2%. The protection device consists of a trigger on transistors VT6, VT7 and a threshold element on transistor VT9. As soon as the current through any of the output transistors exceeds 8...9 A, transistor VT9 opens, and its collector current opens trigger transistors VT6, VT7.
AF power amplifier
The AF amplifier offered to the attention of radio amateurs has very low harmonic and intermodulation distortion coefficients, it is relatively simple, and can withstand short-term short circuit in the load, does not require remote elements for thermal stabilization of the current of the output stage transistors.
Main technical characteristics:
Maximum power at 4 Ohm load, W.................................... 80
Nominal frequency range, Hz...................20....20000
Harmonic distortion at maximum output power 80 W, %, at frequency:
1 kHz................................................... ................................ 0.002
20..................................................................................... 0,004
Intermodulation distortion coefficient, %...................0.0015
Output voltage slew rate, V/µs...................................40
To increase the input resistance, transistors VT1, VT2 were introduced into the AF amplifier. This facilitated the operation of op-amp DA1 and made it possible to ensure a stable base-emitter voltage of transistors VT3, VT4 when the temperature changes.
Resistor R14 sets the symmetry of the arms of the amplifier's output stage. 
Simple power amplifier
Main technical characteristics:
Input voltage, V................................................... ................1.8
Input impedance, kOhm................................................... .......10
Rated output power, W, .................................... 90
Nominal frequency range, Hz................................ 10...20000
Harmonic coefficient, %, at frequency, Hz:
200 .................................................................................... 0,01
2000 ............................................................................ 0,018
20000 ............................................................................... 0,18
Relative noise level, dB, no more........................... -90
Output voltage slew rate, V/µs.................................. 17
The power amplifier consists of a voltage amplification stage on a high-speed op-amp DA1 and an output cascade on transistors VT1 - VT4. The transistors of the complementary pair of the pre-terminal stage (VT1 - VT2) are connected according to a circuit with a common base, and the final stage (VT3 - VT4) - with a common emitter. This inclusion of powerful composite transistors of the final stage provides signal amplification not only in current, but also in voltage. The symmetry of the arms of the output stage helps to reduce the nonlinear distortions introduced by the amplifier. For the same purpose, it is covered by a common OOS circuit, the voltage of which is removed from the output of the amplifier and, through resistor R3, supplied to the non-inverting input of the op-amp. Capacitors C4, C5, shunt resistors R6, R7 reduce step-type distortion. The R12C6 circuit prevents self-excitation of the amplifier in the region of higher audio frequencies and increases the stability of its operation under the reactive nature of the load. The gain depends on the ratio of the resistances of resistors R2, R3. With the denominations indicated in the diagram, it is equal to 10.
Any unstabilized bipolar source with a voltage of 25...45 V is suitable to power the amplifier. Instead of KT503D transistors, you can use KT503E, instead of KT502D - KT502E. Transistors KT827B and KT825D can be replaced by composite transistors KT817G + KT819GM and KT816G + KT818GM, respectively.
200 W power amplifier with power supply
Main technical characteristics:
Nominal frequency range, Hz.................................... 20...20000
Maximum output power, W, into a 4 Ohm load........ 200
Harmonic coefficient, %, with output power 0.5..150 W at frequency, kHz
1 ..........................................................................................0,1
10 .................................................................................... 0,15
20 .................................................................................... 0,2
Efficiency, %................................................... ............................................... 68
Rated input voltage, V.................................................... 1
Input impedance, kOhm................................................... .. 10
Output voltage slew rate, V/µs.................................... 10
The pre-amplification stage is made on a high-speed op-amp DA1 (K544UD2B), which, along with the necessary voltage gain, ensures stable operation of the amplifier with deep feedback. Feedback resistor R5 and resistor R1 determine the gain of the amplifier. The output stage is made using transistors VT1 - VT8. Zener diodes VD1, VD2 stabilize the op-amp supply voltage, which is simultaneously used to create the required bias voltage of the output stage. Capacitors C4, C5 are corrective. As the capacitance of capacitor C5 increases, the stability of the amplifier increases, but at the same time nonlinear distortion increases, especially at higher audio frequencies. The amplifier remains operational when the supply voltage is reduced to 25 V.
A conventional bipolar power supply can be used as a power source, circuit diagram which Powerful composite transistors VT7 and VT8, connected according to the emitter follower circuit, provide fairly good filtering of supply voltage ripples with the mains frequency and stabilization of the output voltage thanks to the zener diodes VD5 - VD10 installed in the transistor base circuit. Elements L1, L2, R16, R17, C11, C12 eliminate the possibility of high-frequency generation. Resistors R7, R12 of the power supply represent a segment copper wire PEL, PEV-1 or PELSHO with a diameter of 0.33 and a length of 150 mm, wound on the body of the MLT-1 resistor. The power transformer is made on a toroidal magnetic core made of electrical steel E320, 0.35 mm thick, strip width 40 mm, internal diameter of the magnetic core 80, outer diameter 130 mm. The network winding contains 700 turns of PELSHO 0.47 wire, the secondary winding contains 2x130 turns of PELSHO 1.2 mm wire.
Instead of the K544UD2B op-amp, you can use K544UD2A, K140UD11 or K574UD1. Each of the KT825G transistors can be replaced with composite transistors KT814G, KT818G, and KT827A with composite transistors KT815G, KT819G. Diodes VD3 - VD6 UMZCH can be replaced with any high-frequency silicon diodes, VD7, VD8 - with any silicon diodes with a maximum forward current of at least 100 mA. Instead of KS515A zener diodes, you can use D814A (B, C, D, D) and KS512A zener diodes connected in series.
BP
A low frequency amplifier (LFA) is a device for amplifying electrical oscillations corresponding to the frequency range audible to the human ear, i.e. the LFA should amplify in the frequency range from 20 Hz to 20 kHz, but some VLFs can have a range of up to 200 kHz. The ULF can be assembled as a separate device, or used in more complex devices - televisions, radios, radios, etc.
The peculiarity of this circuit is that pin 11 of the TDA1552 microcircuit controls the operating modes - Normal or MUTE.
C1, C2 - pass-through blocking capacitors, used to cut off the constant component of the sinusoidal signal. It is better not to use electrolytic capacitors. It is advisable to place the TDA1552 chip on a radiator using heat-conducting paste.
In principle, the presented circuits are bridge ones, because in one housing of the TDA1558Q microassembly there are 4 amplification channels, so pins 1 - 2, and 16 - 17 are connected in pairs, and they receive input signals from both channels through capacitors C1 and C2. But if you need an amplifier for four speakers, then you can use the circuit option below, although the power will be 2 times less per channel.
The basis of the design is the TDA1560Q class H microassembly. The maximum power of this ULF reaches 40 W, with a load of 8 ohms. This power is provided by approximately twice the increased voltage due to the operation of the capacitors.
The output power of the amplifier in the first circuit assembled on the TDA2030 is 60W at a load of 4 Ohms and 80W at a load of 2 Ohms; TDA2030A 80W at 4 ohm load and 120W at 2 ohm load. The second circuit of the considered ULF is already with an output power of 14 Watts.
This is a typical two-channel ULF. With a little wiring of passive radio components, this chip can be used to build an excellent stereo amplifier with an output power of 1 W on each channel.
The TDA7265 microassembly is a fairly powerful two-channel Hi-Fi class AB amplifier in a standard Multiwatt package; the microcircuit has found its niche in high-quality stereo technology, Hi-Fi class. The simple switching circuit and excellent parameters made the TDA7265 a perfectly balanced and excellent solution for building high-quality amateur radio equipment.
The microassembly is a quad class AB amplifier designed specifically for use in car audio devices. Based on this microcircuit, you can build several high-quality ULF options using a minimum of radio components. The microcircuit can be recommended to beginning radio amateurs for home assembly of various speaker systems.
The main advantage of the amplifier circuit on this microassembly is the presence of four channels independent of each other. This power amplifier operates in AB mode. It can be used to amplify various stereo signals. If desired, you can connect it to the speaker system of a car or personal computer.
The TDA8560Q is just a more powerful analogue of the TDA1557Q chip, widely known to radio amateurs. The developers have only strengthened the output stage, thanks to which the ULF is perfectly suited to a two-ohm load.
The LM386 microassembly is a ready-made power amplifier that can be used in designs with low supply voltage. For example, when powering the circuit from a battery. LM386 has a voltage gain of about 20. But by connecting external resistances and capacitances, the gain can be adjusted up to 200, and the output voltage automatically becomes equal to half the supply voltage.
The LM3886 microassembly is a high quality amplifier with an output power of 68 watts into a 4 ohm load or 50 watts into 8 ohms. At peak moment, the output power can reach 135 W. A wide voltage range from 20 to 94 volts is applicable to the microcircuit. Moreover, you can use both bipolar and unipolar power supplies. The ULF harmonic coefficient is 0.03%. Moreover, this is over the entire frequency range from 20 to 20,000 Hz.
The circuit uses two ICs in typical inclusion- KR548УH1 as a microphone amplifier (installed in the PTT switch) and (TDA2005) in a bridge connection as a final amplifier (installed in the siren housing instead of the original board). A modified alarm siren with a magnetic head is used as an acoustic emitter (piezo emitters are not suitable). The modification consists of disassembling the siren and throwing out the original tweeter with an amplifier. The microphone is electrodynamic. When using an electret microphone (for example, from Chinese handsets), the connection point between the microphone and the capacitor must be connected via a ~4.7K resistor to +12V (after the button!). The 100K resistor in the K548UH1 feedback circuit is better set with a resistance of ~30-47K. This resistor is used to adjust the volume. It is better to install the TDA2004 chip on a small radiator.
Test and operate - with the emitter under the hood and the PTT in the cabin. Otherwise, squealing due to self-excitation is inevitable. A trimmer resistor sets the volume level so that there is no strong sound distortion and self-excitation. If the volume is insufficient (for example, a bad microphone) and there is a clear reserve of emitter power, you can increase the gain of the microphone amplifier by several times increasing the value of the trimmer in the feedback circuit (the one according to the 100K circuit). In a good way, we would also need a primabass that would prevent the circuit from self-exciting - some kind of phase-shifting circuit or a filter for the excitation frequency. Although the scheme works fine without complications