A simple adjustable sound amplifier on kt 805. The simplest low-frequency transistor amplifiers

They are a thing of the past, and now, in order to assemble any simple amplifier, you no longer have to suffer with calculations and rivet printed circuit board large sizes.

Now almost all cheap amplifying equipment is made on microcircuits. The most widely used TDA chips for amplifying the audio signal. They are currently used in car radios, in active subwoofers, in home acoustics and in many other audio amplifiers and look something like this:

Pros of TDA chips

1. In order to assemble an amplifier on them, it is enough to supply power, connect speakers and several radio elements.
2. The dimensions of these microcircuits are quite small, but they will need to be placed on a radiator, otherwise they will get very hot.
3. They are sold at any radio store. On Ali, something is expensive, if you take it at retail.
4. They have built-in various protections and other options, such as mute and so on. But according to my observations, the protections do not work very well, so the microcircuits often die either from overheating or from. So it is advisable not to close the microcircuit pins to each other and not to overheat the microcircuit, squeezing all the juice out of it.
5. Price. I wouldn't say they are very expensive. For the price and functions they perform, they have no equal.

Single-channel amplifier on TDA7396

Let's assemble a simple single-channel amplifier on the TDA7396 chip. At the time of this writing, I took it at a price of 240 rubles. The datasheet for the microcircuit said that this microcircuit can deliver up to 45 watts into a 2 ohm load. That is, if you measure the resistance of the speaker coil and it will be about 2 ohms, then it is quite possible to get a peak power of 45 watts on the speaker.This power is quite enough to arrange a disco in the room not only for yourself, but also for your neighbors and at the same time get a mediocre sound, which, of course, cannot be compared with hi-fi amplifiers.

Here is the pinout of the chip:

We will assemble our amplifier according to the typical scheme that was attached in the datasheet itself:

We feed +Vs to leg 8, and we don’t feed anything to leg 4. So the diagram will look like this:

Vs is the supply voltage. It can be from 8 to 18 volts. “IN+” and “IN-” - here we serve a weak sound signal. We hook the speaker to the 5th and 7th legs. We put the sixth leg on the minus.

Here is my flush mount build

I did not use capacitors at the 100nF and 1000uF power input, since I have pure voltage coming from the power supply.

Rocked the speaker with the following parameters:

As you can see, the resistance of the coil is 4 ohms. The frequency band indicates that it is a subwoofer type.

And this is what my sub looks like in a self-made case:

I tried to shoot a video, but the sound on the video is very bad for me. But still, I can say that it was already pecking from the phone at medium power so that the ears were wrapped, although the consumption of the entire circuit in working form was only about 10 watts (we multiply 14.3 by 0.73). In this example, I took the voltage, as in a car, that is, 14.4 Volts, which fits well into our operating range from 8 to 18 Volts.

If you do not have a powerful power source, then it can be assembled according to this scheme.

Do not go in cycles in this chip. These TDA chips, as I said, there are many types. Some of them amplify the stereo signal and can output sound to 4 speakers at once, as is done in car radios. So do not be lazy to rummage through the Internet and find a suitable TDA. After completing the assembly, let your neighbors check out your amplifier by unscrewing the volume knob for the entire balalaika and leaning the powerful speaker against the wall).

But in the article I assembled an amplifier on a TDA2030A chip

It turned out very well, since the TDA2030A has the best performance than TDA7396

I will also add, for a change, another circuit from a subscriber whose amplifier on the TDA 1557Q has been working properly for more than 10 years in a row:

Amplifiers on Aliexpress

On Ali, I also found kit kits on TDA. For example, this one stereo amplifier 15 watts per channel for $1. This power is enough to hang out with your favorite tracks in the little room

You can buy.

But he's ready right now

Anyway, there are a lot of these amplifier modules on Aliexpress. Click on this link and choose any amplifier you like.

Single transistor amplifier- here is the design of a simple ULF on a single transistor. It was with such schemes that many radio amateurs began their journey. Once having assembled a simple amplifier, we always strive to make a more powerful and high-quality device. And so everything goes on increasing, there is always a desire to make an impeccable power amplifier.

Shown below the simplest circuit the amplifier is made on one bipolar transistor and six electronic components, including a speaker. This design of a low-frequency sound amplifying device was created just for beginner radio amateurs. Its main purpose is to make clear the simple principle of operation of the amplifier, so it is assembled using a minimum number of electronic elements.

This amplifier naturally has big power, for starters, it is large and not needed. However, if you install a more powerful transistor and raise the supply voltage a little, then you can get about 0.5 watts at the output. And this is already considered quite decent power for an amplifier having such a design. In the diagram, for clarity, a bipolar transistor with n-p-n conductivity is used, but you can use any and with any conductivity.

To get 0.5 W at the output, it is best to use powerful bipolar transistors such as KT819 or their foreign counterparts, for example 2N6288, 2N5490. You can also use silicon transistors such as KT805, their foreign counterpart - BD148, BD149. The capacitor in the output path circuit can be set to 0.1mF, although its nominal value does not play a big role. Nevertheless, it forms the sensitivity of the device relative to the frequency of the sound signal.

If you put a capacitor with a large capacity, then the output will be predominantly low frequencies, and the high ones will be cut off. Conversely, if the capacitance is small, then low frequencies will be cut, and high frequencies will be skipped. Therefore, this output capacitor is selected and installed based on your preference for audio range. The supply voltage for the circuit must be selected in the range from 3v - to 12v.

I would also like to clarify - this power amplifier is presented to you only for demonstration purposes, to show the principle of operation of such a device. The sound of this device will certainly be at a low level and cannot be compared with high-quality devices. When the playback volume is increased, distortion in the form of wheezing will occur in the speaker.

Readers! Remember the nickname of this author and never repeat his schemes.
Moderators! Before you ban me for insults, think that you "let an ordinary gopnik to the microphone", who should not even be allowed close to radio engineering and, moreover, to teaching beginners.

Firstly, with such a switching scheme, a large D.C., even if the variable resistor is in the right position, that is, music will be heard. And with a large current, the speaker is damaged, that is, sooner or later, it will burn out.

Secondly, in this circuit there must be a current limiter, that is, a constant resistor, at least 1 KΩ, connected in series with a variable one. Any do-it-yourselfer will turn the variable resistor regulator all the way, it will have zero resistance and a large current will go to the base of the transistor. As a result, the transistor or speaker will burn out.

A variable capacitor at the input is needed to protect the sound source (this should be explained by the author, because immediately there was a reader who removed it just like that, considering himself smarter than the author). Without it, only those players in which such protection is already installed at the output will work normally. And if it is not there, then the player's output may be damaged, especially, as I said above, if you unscrew the variable resistor "to zero". In this case, the output of an expensive laptop will be energized from the power source of this penny trinket and it can burn out. Homemade ones are very fond of removing protective resistors and capacitors, because "it works!" As a result, the circuit can work with one sound source, but not with another, and even an expensive phone or laptop can be damaged.

The variable resistor, in this circuit, should only be a trimmer, that is, it should be adjusted once and closed in the case, and not brought out with a convenient handle. This is not a volume control, but a distortion control, that is, it selects the operating mode of the transistor so that there is minimal distortion and that smoke does not come out of the speaker. Therefore, it should never be accessible from the outside. It is IMPOSSIBLE to adjust the volume by changing the mode. For this you need to "kill". If you really want to adjust the volume, it's easier to turn on another variable resistor in series with the capacitor, and now it can already be output to the amplifier case.

In general, for the simplest circuits - and in order to work right away and not to damage anything, you need to buy a TDA-type chip (for example, TDA7052, TDA7056 ... there are many examples on the Internet), and the author took a random transistor that was lying around in his desk. As a result, gullible amateurs will look for just such a transistor, although its gain is only 15, and the allowable current is as much as 8 amperes (it will burn any speaker without even noticing).

Portable speaker for a player or phone on a tda2822m chip Amplifier test photo:

The following figure lists the required parts:

Almost any of the medium and high power bipolar transistors can be used in the circuit. n-p-n structures, for example, KT 817. It is desirable to put a film capacitor at the input, with a capacity of 0.22 - 1 μF. An example of film capacitors in the following photo:

I bring a drawing of a printed circuit board from the program Sprint layout :


The signal is taken from the output of an mp3 player or telephone, ground and one of the channels are used. In the following figure, you can see the wiring diagram for the Jack 3.5 plug, for connecting to a signal source:


If desired, this amplifier, like any other, can be equipped with a volume control by connecting a 50 KΩ potentiometer according to the standard scheme, 1 channel is used:


In parallel with the power supply, if there is no high-capacity electrolytic capacitor in the power supply after the diode bridge, you need to supply an electrolyte of 1000 - 2200 uF, with an operating voltage greater than the supply voltage of the circuit.
An example of such a capacitor:

You can download the printed circuit board of an amplifier on a single transistor for the sprint-layout program in the My files section of the site.

You can evaluate the sound quality of this amplifier by watching the video of its work on our channel.

Amplifiers on KT930A - KT971A are designed to work with a transceiver having Pout from 10W to 20W, respectively, at output power levels: on KT930A 144 - 70W, on KT930A 432 - 60W, on KT931A 144MHz - 120W, on KT970A 144MHz - 130W - 145w.

Amplifiers are designed for round-the-clock operation and have a good margin of "strength", especially on KT970A and KT971A. At such levels of Pout, the amplifiers have maximum efficiency and Ku. The efficiency of amplifiers, depending on the option, is from 57% to 65%. The gain is from 8 to 9. The amplifiers use a fan blown from a PC power supply located 30mm above the transistor. It cools the transistor case and the inside of the radiator well. It is useless to cool the outside.

From the amplifiers built according to the proposed scheme, the following power levels were obtained: KT930A 144 - 80W, KT930A 432 - 65W, KT931A 144 - 130W, KT970A 432 - 160W, KT971A 144 - 180W (the source did not allow further). At these Pout levels, additional tuning of the shading circuits is required. It is desirable to equip amplifiers with high power with a control and protection system.

The input and output circuits are designed for the specified transistor types and amplifier capacities only. During the operation of the amplifier, with an increase in the collector current, the values ​​of its conductivities change in magnitude, and even in sign. Accordingly, each output power level has its own matching circuit. On an output circuit optimal for 60W, it is not possible to get 100W even though Ik continues to rise. The quiescent current affects the dynamics of changes in conductance, which means that it is impossible to change the quiescent current after adjustment.

The operating point of the transistor on the vector diagram is located below and away from the axis of active resistances. Zin and Zout have reactive components 2-5 times more than active ones. These values ​​are of the order Z = (1-3) +\\- J(3-15) ohm. The matching task is performed by three external links (the more, the more accurate), each of which is not a complete resistance transformer, which implies resonances, but only by reducing it turns purely active 50 (75) ohm loads into some kind of Z with a smaller R, but with a larger Jx, that is, the links operate at frequencies other than resonant. Three links is one impedance converter. Resonance further - smaller currents flow through the elements of the system. You don’t need a thick wire for L and powerful trimmers. Resonant currents also do not flow through the transistor crystal, which reduces its heating. All this allows you to increase the input and output power.

Features of mounting RA 144 MHz:

The amplifiers use multilayer ceramic capacitors MCH0805 (chip) or

similar ones are older, with soldered radial leads and MO10,11 with leads.

On 144, the base chain is used of the old (familiar) type - you can still do it here.

Board - single-sided SF 1.5mm size 55mm x 110mm with a hole for the transistor

along the axis of the board. The board and the transistor (with paste) are attached to a 110 x 120mm radiator (needle is better).

Collector strip - double-sided SF 1.5mm, size 5.5mm x 50mm. In the transistor, the foil is kept at a distance of 6 mm from the ceramic. Further, only 6mm pads go at intervals. Mark the strip so that the rest of the details fit. The foil between the pads is removed with a well-heated soldering iron.

The base strip is a double-sided SF 1.5mm measuring 5.5mm x 45mm. The transistor has foil

is kept at a distance of 11mm from the ceramic. Next come only 6mm pads.

Both strips are 20mm from the edge of the board.

The bottom of the strips and their location on the board should be irradiated, put in place and from the sides run along the board with a 90W soldering iron.

The transistor leads are cut flush with the collector and base lengths of 5 mm, the plane of its case coincides with the bottom plane of the board, the emitters are bent and soldered to the top of the board. The collector and base are soldered to the beginning of their strips, which touch the body ceramics.

The power strip is 5mm from one of the edges of the board for soldering small chips.

Capacitors KT4-23 (in plastic) have 2mm leads. One completely falls on the strip.

The values ​​​​and design data of the elements of Ra 144 MHz (Fig. 1):

The base choke (D1) is a 6-hole ferrite (from older PCs). A 0.35mm wire is threaded through them. You can use DM chokes with a thick wire and low inductance.

The place of soldering is 7mm from the ceramics of the transistor. PEV, CU are slightly worse than RPS.

Collector choke (D2) - PSR (PEV, CU) O 0.7mm 5vit on the mandrel O 3mm, pitch - 1.5mm

The soldering point is 3mm from the ceramics of the transistor, next to L2.

The second collector choke (D3) - PEV O 0.4 - 20 vit on the mandrel O 3mm, continuous winding. Own resonant frequencies D1 and D2 are far apart.

L1 - wire RPS (PEV, CU) O 0.7mm - 3 turns with a pitch of 1mm on a mandrel O 4mm.

The soldering point is 8mm from the ceramics of the transistor, after D1.

L2 (KT930 - 971) - wire 16mm long PSR (PEV, CU) O 1.4-1.6mm bent with a bracket 4mm high.

L3 (KT930,931) - 2 turns of RPS (PEV, CU) O 1.4-1.6mm on the mandrel O 6mm with a step of 2mm

(KT971 - 1 vit).

L4 (KT930,931) - 1 turn of RPS (PEV, CU) O 1.4-1.6mm on a mandrel O 6mm (KT971 - 2 turns).

C1,2,9 - KT4-23 = 4-20 pf. C11,13,15, 17 - K10 (chip) 0.5 - 1.0? f 50v. C12,14,16 - K10 -1n 50v.

C7,10 -МЧ0805 - 47pf 250v. For KT971A C10 - MCH0805 27pf 250v.

For KT971A C9 - MCH0805 20pf 250v + KT2-19 = 1.5-15pf (lying on its side).

C8 - MCH0805 - 110pf 250v.

C3-6 - 4 x 100pf 50v, MO10, leads - 1mm. Solder in 5-6mm from the ceramics of the transistor.

R1 - 10 ohm MLT 2 watts. R2-3 - 2 x 360 ohm MLT 2W - selection for Ik0 = 60mA.

R4 - 10-15ohm MLT 0.5W

T1 - KT930A/KT 931A/971A. Their currents are listed in the same order.

T2 - KT818B - the base current stabilizer is attached to the radiator next to the board.

The fan from the PC power supply is mounted above the ceramics of the transistor at a height of 25-30mm.

D1 - D223B - reverse polarity surge protection.

R6 - 1kom 2W - load for interference during switching when the RA is on and the load is removed in case of unauthorized switching of TRSV to transmission by the computer when it is loaded - port polling.

R5 - 510 ohm 2W - some compensation for excess TRSV power (if necessary).

After assembling and installing Ik0 = 60mA, connect the standard load and the measuring system. TX switch to CW mode - points 100 lpm, apply 30% power to the input and adjust C1, C2, C9 (144) or C1, C4, C9 (432) to the maximum Pout. Do the same by gradually increasing Pin to 60% and 100% (Pin is indicated approximately). Adjust the input at each level Рout. The instruments will show about 75% of the Ikmax and Pmax levels (in carrier mode). Ikmax when working on a matched load at Pmax should be about 4a - KT930A, 7a - KT931A, 8a - KT971A.

You can not increase the buildup, if at the same time it does not grow output power amplifier to the indicated levels. Burn the transistor. You did something wrong or soldered capacitors of a different type, and transistors are different. At each stage of tuning, it is necessary to control the collector current and the temperature of the transistor case. It should not exceed 50? (immediately after turning off the fan).

With 100% copying of the design, excluding “what if?”, And your sufficient experience, setting up should not take more than 5 minutes. The use of surrogate loads, reflectometers when setting up is not allowed. When working on an antenna, it is desirable that it be real, not from advertising. Having all the details, the amplifier is made in 2-3 hours.

When placing the RA in the case, it must have openings for air intake and outlet.

Two RAs can be placed on one 120mm x 180mm radiator with a 30mm spacing. The fan is fixed in the center of the radiator 30 mm above the ceramics of the transistors.

Features of mounting RA 432 MHz the same as in RA 144 MHz with one difference:

On the base and collector strips, the foil is kept 12mm away from the ceramics of the transistor.

Values ​​and design data of the elements of RA 432 MHz (Fig. 2):

The basic inductor (D1) is the same as the PA 144 MHz. The point of its soldering is 6mm from the KT ceramics.

The collector choke (D2) is of the same design as the RA 144 MHz, but contains 4 turns.

The place of its soldering on the strip is 6 mm from the CT ceramics.

D3 - same as RA 144 MHz.

L1,L2,L5,L6 are made from wire RPS (PEV, CU) O 1.6mm.

L1,L6 - wire 34mm long, bent into a shackle on a mandrel O 10mm. Squeeze the bottom of the bow a little.

L2,L5 - wire 22mm long, bent into a shackle on a mandrel O 6mm. -- . -- . -- . -- . -- . -- . --

L3,L4 - sections of foil on strips near the transistor 12mm long.

C1 - KT4-23 = 2-10pf.

C2 - MCh0805 - no for KT930A and 6pf 250v for KT970A.

C3 - MCH0805 - 47pf 250v.

C4 - KT4-23 - no for KT930A and 4-20pf for KT970A.

C5 - MCH0805 - 22pf 250v for KT930A and 27pf 250v for KT970A.

The place of soldering the center of the capacitors C4, C5 on the strips is 9mm from the case ceramics.

C6 - MCH0805 27pf 250v.

C7 - KT4 -23 = 4-20pf for KT930A and MCH0805 - 22pf 250v for KT970A.

The soldering place for the center of capacitors C6, C7 is 9mm from the case ceramics.

C8 - MCH0805 - 75pf 250v for KT930A and 110pf 250v for KT970A.

C9 - KT2-18 - 1.5-10pf (lying on its side) or another with convenient minimum leads.

C10 - MCH0805 - 6pf 250v for KT930A and 15pf 250v for KT970A.

C15 - K10 (chip) 0.5-1? 50th century

The remaining blocking pairs are the same as those of RA 144 MHz - K10 (chip) 1n + 0.5 - 1? f 50v.
The setting procedure for RA 144 and RA 432 is the same. Ikmax KT930A = 3.5a, KT970A = 8a.

It is more economical to power the base from a lower voltage source (14V or 5V). At 14v R2.3 - about 75 ohms. When the base is powered according to the scheme (from 28v), the current Ik0 is the difference between the current consumption in operating mode and the current of the divider itself (~ 147mA). The total current is ~ 200mA.

The use of trimmers KT4-23 compensates for the lack of the required capacitance ratings. In the photo, capacitors with a blue border and soldered radial leads are an analogue of MCh0805.

Fig.1 RA 144MHz

Fig. 2 RA 432 MHz

Fig.3 RA 144 KT931A RA 432 KT930A