Homemade amplifier with transistors. The best quality sound amplifier
The circuits of low-frequency amplifiers differ little from each other, except in the capacity of the capacitors used. Despite the fact that usually a low-frequency amplifier has at least a couple of stages, to gain experience you can try to assemble a simple amplifier with just one transistor (and, accordingly, with one cascade).
The single-stage amplifier circuit proposed below is extremely simple, and can be equally well executed using either wall-mounted (based on conventional wires and leads) or printed circuit (based on printed wires, electrically conductive strips) installation.
Fig. 1: Single-stage transistor circuit
Circuits for assembling transistors have a number of symbols:
- R1 (2, 3, 4...) – resistors;
- C1 (2, 3, 4...) – capacitors;
- B1 (2, 3, 4...) – speaker, telephone, etc.;
- T1 (2, 3, 4…) – .
The feasibility of assembling a single-stage amplifier is justified solely by the need to obtain experimental experience, and its practical application will demonstrate sufficient low quality sound similar to that observed in modern Chinese technology.
To assemble a simple amplifier you will need a number of parts:
- Transistor KT 817 (or similar);
- 5 kOhm resistor, 0.25 Watt;
- Film capacitor 0.22 - 1 microfarad;
- A speaker delivering a load of 4-8 Ohms (1 - 3 Watts);
- 9 Volt power supply;
- Signal source (1 channel and ground).
The value of the bias resistor R1 reaches tens of kOhms and is determined experimentally. The fact is that this indicator is calculated taking into account the supply voltage of the device, the resistance of the telephone capsule, and the transmission coefficient characteristic of the selected type of transistor. The starting point can be a load resistance increased by at least a hundred times.
The capacitor (in the diagram is designated as C1) and the level of its capacitance varies in the range from 1 to 100 microfarads, with increasing capacitance the device gains the ability. The purpose of a capacitor (also called a decoupling capacitor) is to pass alternating current and filter out direct current, preventing the circuit from shorting out.
For this circuit, it is appropriate to use a bipolar transistor with n-p-n structure and power of average and high level. It is advisable to take a film capacitor. The received signal can be received through the output of the MP3 player. The device assembled according to this scheme can be equipped with a potentiometer (50,000 Ohms), which allows you to adjust the volume.
If there is no electrolytic capacitor with a large capacity in the power supply unit, you will need to install an electrolyte of 1000 - 2200 microfarads, which has an operating voltage greater than in the circuit.
Anyone who has no experience working with electronics should know that when soldering, components can very easily overheat. To prevent this from happening, it is best to use 25 Watt soldering irons, and you need to stop soldering after every 10 seconds of continuous exposure.
Compared with the given circuit of a single-stage low-frequency amplifier, a two-stage one has much best characteristics, but its assembly is not much more difficult. To construct it, you only need to connect two simple cascades in series. However, different types of connections can be used, which, of course, affect the quality and characteristics of signal transmission. But in the simplest version, you can simply connect the output of the first stage to the input of the second stage directly or through a resistor. A connection of this type is respectively called direct or resistor. The degree of signal amplification in this case is equal to the multiplied gain factors of each of the stages. Unfortunately, a subsequent increase in the number of stages in the amplifier does not give a similar effect. The problem is that the gain value is determined in a complex manner and depends quite strongly on the time delay, that is, the phase change.
Modern modifications of low-frequency amplifiers, usually listed in magazines for radio amateurs, are designed to reduce the level of nonlinear distortion and increase output power, as well as modify other parameters in order to increase the efficiency of the device.
But at the same time, if the task is to establish the operation of certain devices, as well as to resolve some controversial issues experimentally, then it may be necessary simplest option amplifier, assembled in literally a quarter of an hour. The main requirement for such a device will be a minimum number of scarce components, as well as the ability to operate with a wide range of voltage and resistance levels.
When operating a low-frequency amplifier, do not forget that its performance is highly dependent on temperature conditions, especially for home-made devices.
Write comments, additions to the article, maybe I missed something. Take a look at, I will be glad if you find something else useful on mine.
They are becoming a thing of the past, and now, in order to assemble any simple amplifier, you no longer have to suffer with calculations and riveting printed circuit board large sizes.
Now almost all cheap amplification equipment is made on microcircuits. The most widespread are TDA chips for amplifying audio signals. Currently used in car radios, powered subwoofers, home speakers and many other audio amplifiers, they look something like this:
Pros of TDA chips
- In order to assemble an amplifier on them, it is enough to supply power, connect speakers and several radio elements.
- The dimensions of these microcircuits are quite small, but they will need to be placed on a radiator, otherwise they will get very hot.
- They are sold at any radio store. There are some things on Ali that are a little expensive if you buy them at retail.
- They have built-in various protections and other options, such as muting the sound, etc. But according to my observations, the protections do not work very well, so microcircuits often die either from overheating or from. So it is advisable not to short-circuit the pins of the microcircuit with each other and not to overheat the microcircuit, squeezing all the juices out of it.
- Price. I wouldn't say they are very expensive. In terms of price and functions, they have no equal.
Single-channel amplifier on TDA7396
Let's build a simple single-channel amplifier using the TDA7396 chip. At the time of writing, I took it at a price of 240 rubles. The datasheet for the chip said that this chip can output up to 45 Watts into a 2 Ohm load. That is, if you measure the resistance of the speaker coil and it is about 2 ohms, then it is quite possible to get a peak power of 45 watts from 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 mediocre sound, which, of course, cannot be compared with hi-fi amplifiers.
Here is the pinout of the microcircuit:
We will assemble our amplifier according to a typical diagram, which was attached in the datasheet itself:
We apply +Vs to leg 8, and nothing to leg 4. Therefore, 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 the weak sound signal. We attach a speaker to the 5th and 7th legs. We set the sixth leg to minus.
Here is my wall mounted assembly
I did not use capacitors at the power input of 100nF and 1000uF, since I already have pure voltage coming from the power supply.
I rocked the speaker with the following parameters:
As you can see, the coil resistance is 4 ohms. The frequency band indicates that it is a subwoofer type.
And this is what my sub in a self-made housing looks like:
I tried to take a video, but the sound on the video is very poor. But I can still say that the phone at medium power was already hammering so hard that my ears were turning, although the consumption of the entire circuit in working form was only about 10 watts (multiply 14.3 by 0.73). In this example, I took the voltage as in a car, that is, 14.4 Volts, which is well within our operating range from 8 to 18 Volts.
If you do not have a powerful power source, then you can assemble it according to this diagram.
Don't get hung up on this particular chip. These TDA chips, as I already 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 don’t be lazy to scour the Internet and find a suitable TDA. After completing the assembly, let your neighbors check out your amplifier by turning the volume knob all the way to the balalaika and leaning the powerful speaker against the wall).
But in the article I assembled an amplifier using a TDA2030A chip
It turned out very well, since the TDA2030A has better characteristics than the TDA7396
For variety, I’ll also attach another diagram from a subscriber whose TDA 1557Q amplifier has been working properly for more than 10 years in a row:
Amplifiers on Aliexpress
I also found kit kits on Ali on TDA. For example, this stereo amplifier is 15 watts per channel and costs $1. This power is quite enough to hang out in your room listening to your favorite tracks.
You can buy it.
And here it's ready right away
And in general, there are a lot of these amplifier modules on Aliexpress. Click on this link and choose any amplifier you like.
The audio amplifier is the most important component of many electronic devices. This could be playback music files, fire and security alarm systems or sound sensors for various toys. Appliances equipped with built-in low-frequency channels, but for home design electronic homemade products You may need to make this device yourself.
DIY transistor audio amplifier circuit
The range of sound frequencies that are perceived by the human ear is in the range of 20 Hz-20 kHz, but a device made on a single semiconductor device, due to the simplicity of the circuit and the minimum number of parts, provides a narrower frequency band. IN simple devices, enough to listen to music frequency range 100 Hz-6,000 Hz. This is enough to play music on a miniature speaker or earphone. The quality will be average, but for mobile device quite acceptable.
Scheme simple amplifier sound on transistors can be collected on silicon or germanium products of direct or reverse conduction (p-n-p, n-p-n). Silicon semiconductors are less critical to supply voltage and have less dependence of characteristics on junction temperature.
Audio amplifier circuit with 1 transistor
The simplest audio amplifier circuit using a single transistor includes the following elements:
- Transistor KT 315 B
- Resistor R1 – 16 kom
- Resistor R2 – 1.6 kom
- Resistor R3 – 150 ohm
- Resistor R4 – 15 ohm
- Capacitor C1 – 10.0 µF
- Capacitor C2 – 500.0 µF
This is a device with a fixed base bias voltage, which is set by the divider R1-R2. The collector circuit includes resistor R3, which is the load of the cascade. Between pin X2 and the plus of the power source, you can connect a miniature speaker or earphone, which should have a high resistance. A low-impedance load cannot be connected to the cascade output. Right assembled circuit starts working immediately and does not require configuration.
A higher quality ULF can be assembled using two devices.
The amplifier circuit with two transistors includes more components, but can operate with a low input signal level, since the first element acts as a preliminary stage.
An alternating audio frequency signal is supplied to potentiometer R1, which plays the role of a volume control. Next, through an isolation capacitor, the signal is supplied to the base of the first stage element, where it is amplified to a value that ensures normal operation of the second stage. The collector circuit of the second semiconductor includes a sound source, which can be a small-sized earphone. The bias on the bases is set by resistors R2 and R4. In addition to KT 315, any low-power silicon semiconductors can be used in the audio amplifier circuit with two transistors, but depending on the type of products used, selection of bias resistors may be required.
If you use a push-pull output you can achieve a good volume level and good frequency response. This circuit is made on three common KT 315 silicon devices, but other semiconductors can be used in the device. The big advantage of the circuit is that it can operate on a low-impedance load. Miniature speakers with a resistance of 4 to 8 ohms can be used as a sound source.
The device can be used in conjunction with a player, tuner or other household appliance. The supply voltage of 9 V can be obtained from a Krona battery. If you use KT 815 in the output stage, then at a 4 ohm load you can get up to 1 watt of power. In this case, the supply voltage will need to be increased to 12 volts, and the output elements will need to be mounted on small aluminum heat sinks.
Get good ones electrical characteristics It is almost impossible to use an amplifier assembled on one semiconductor, so high-quality devices are assembled on several semiconductor devices. Such designs produce tens and hundreds of watts at low-impedance loads and are intended for operation in Hi-Fi complexes. When choosing a device, the question may arise as to which transistors can be used to make a sound amplifier. These can be any silicon or germanium semiconductors. ULFs assembled on field-effect semiconductors have become widespread. For low-power devices with low-voltage power supply, you can use silicon products KT 312, KT 315, KT 361, KT 342 or germanium products of the old MP 39-MP 42 series.
A do-it-yourself power amplifier using transistors can be made using the complementary pair KT 818B-KT 819B. This design will require a pre-block, an input stage and a pre-final block. The pre-assembly includes signal level control and tone control for high and low frequencies or a multi-band equalizer. The voltage at the output of the preliminary unit must be at least 0.5 volts. The input node of the power block can be assembled on a high-speed operational amplifier. In order to swing the terminal part, a pre-terminal cascade is required, which is assembled on a complementary pair of medium-power devices KT 816-KT 817. Designs powerful amplifiers low frequencies are distinguished by complex circuitry and big amount components. To properly adjust and configure such a unit, you will need not only a tester, but an oscilloscope and an audio frequency generator.
The modern element base includes powerful MOSFET devices that allow the design of high-class ULFs. They provide signal reproduction in the frequency range from 20 Hz to 40 kHz with high linearity, total harmonic distortion less than 0.1% and output power from 50 W and above. This design is easy to replicate and adjust, but requires the use of a high quality bipolar power supply.
Low frequency amplifier (LF) is integral part most radio devices such as TVs, players, radios and various household appliances. Let's consider two simple two-stage circuits ULF on.
The first version of ULF on transistors
In the first version, the amplifier is built on silicon npn transistors conductivity. The input signal comes through variable resistor R1, which in turn is a load resistor for the signal source circuit. connected to the collector circuit of transistor VT2 of the amplifier.
Setting up the amplifier of the first option comes down to selecting resistances R2 and R4. The resistance value must be selected such that the milliammeter connected to the collector circuit of each transistor shows a current in the region of 0.5...0.8 mA. According to the second scheme, it is also necessary to set the collector current of the second transistor by selecting the resistance of resistor R3.
In the first option, it is possible to use transistors of the KT312 brand, or their foreign analogues, however, it will be necessary to set the correct voltage bias of the transistors by selecting resistances R2, R4. In the second option, in turn, it is possible to use silicon transistors of the KT209, KT361 brands, or foreign analogues. In this case, you can set the operating modes of the transistors by changing the resistance R3.
Instead of headphones, it is possible to connect a high-impedance speaker to the collector circuit of transistor VT2 (both amplifiers). If you need to get more powerful sound amplification, you can assemble an amplifier that provides amplification of up to 15 W.
Portable USB oscilloscope, 2 channels, 40 MHz....
Single transistor amplifier— here is the design of a simple ULF on one transistor. It was with similar schemes that many radio amateurs began their journey. Once we have assembled a simple amplifier, we always strive to produce a more powerful and high-quality device. And so everything goes on and on, there is always a desire to make an impeccable power amplifier.
Shown below simplest scheme The amplifier is made of one bipolar transistor and six electronic components, including a speaker. This design of a device that amplifies low-frequency sound was created just for beginner radio amateurs. Its main purpose is to make it clear the simple principle of operation of the amplifier, so it is assembled using a minimum number of radio-electronic elements.
This amplifier naturally has low power; to begin with, it is large and not needed. However, if you install a more powerful transistor and raise the supply voltage a little, you can get about 0.5 W at the output. And this is already considered quite decent power for an amplifier with such a design. In the diagram, for clarity, a bipolar transistor with n-p-n conductivity is used, but you can use any of them with any conductivity.
To get 0.5 W output, it is best to use powerful bipolar transistors like KT819 or their foreign analogs, for example 2N6288, 2N5490. You can also use silicon transistors of the KT805 type, their foreign analogues are 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 shapes the sensitivity of the device relative to the frequency of the sound signal.
If you install a capacitor with a large capacity, then the output will be predominantly low frequencies, and the tall ones will be cut off. And vice versa, if the capacitance is small, then low frequencies will be cut and high frequencies will be passed through. Therefore, this output capacitor is selected and installed based on your preferences regarding the audio range. The supply voltage for the circuit must be selected in the range from 3v to 12v.
I would also like to clarify that 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 of course 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 appear in the dynamics.
