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Assemble a powerful amplifier using complementary transistors. Powerful transistor amplifier. Two-stage transistor amplifier

28.09.2014
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On the NCP2809 chip you can assemble high high quality amplifier AF power for headphones. Amplifier output power 135 mW (16 Ohms) per channel. The microcircuit is characterized by a low supply voltage from 2.2V to 5.5V, and the microcircuit can also be connected directly to the battery without a voltage stabilizer. An output power of 135mW is achieved with a supply voltage of 5V at the load...
04.11.2014
The stereo amplifier is designed for a small speaker. It is made on KA2206 and develops a power of 3 W per channel with a load resistance of 4 Ohms, when powered by a constant voltage from 15 to 24 V. Amplifier current consumption is no more than 300mA. The KA2206 microcircuit is connected according to a standard circuit. A signal from the telephone output of the CD-ROM is supplied to its input. ...
28.09.2014
The basis of the frequency meter is IC K155LA3, the frequency meter consists of an input device, a Schmitt trigger, a differentiating circuit, a waiting multivibrator and a measuring device. The input device is made on VT1 connected according to the emitter follower circuit. VD1 VD2 protect the frequency meter from overloads. From the input device, the signal is fed to the Schmitt trigger (DD1.1 DD1.2). Next, the formed rectangular pulses through the differentiating...

There was a desire to assemble a more powerful Class A amplifier. Having read a sufficient amount of relevant literature and selected the most from what was offered latest version. It was a 30 W amplifier corresponding in its parameters to high-class amplifiers.

I did not intend to make any changes to the existing routing of the original printed circuit boards, however, due to the lack of original power transistors, a more reliable output stage was chosen using 2SA1943 and 2SC5200 transistors. The use of these transistors ultimately made it possible to provide greater output power amplifier Schematic diagram my version of the amplifier below.

This is an image of boards assembled according to this circuit with Toshiba 2SA1943 and 2SC5200 transistors.

If you look closely, you can see on the printed circuit board along with all the components there are bias resistors, they are 1 W carbon type. It turned out that they are more thermostable. When any high-power amplifier operates, a huge amount of heat is generated, so maintaining a constant rating of the electronic component when heating it is an important condition for the high-quality operation of the device.

The assembled version of the amplifier operates at a current of about 1.6 A and a voltage of 35 V. As a result, 60 W of continuous power is dissipated on the transistors in the output stage. I should note that this is only a third of the power they can handle. Try to imagine how much heat is generated on the radiators when they are heated to 40 degrees.

The amplifier case is made by hand from aluminum. Top plate and mounting plate 3mm thick. The radiator consists of two parts, its overall dimensions are 420 x 180 x 35 mm. Fasteners - screws, mostly with a countersunk stainless steel head and M5 or M3 thread. The number of capacitors was increased to six, their total capacity is 220,000 µF. A 500 W toroidal transformer was used for power supply.

Amplifier power supply

The amplifier device, which has copper busbars of the appropriate design, is clearly visible. A small toroid has been added for controlled feed under the control of an anti-corrosion circuit. direct current. There is also a high-pass filter in the power supply circuit. For all its simplicity, it must be said deceptive simplicity, the board topology of this amplifier produces sound as if without any effort, implying in turn the possibility of its infinite amplification.

Oscillograms of amplifier operation

3 dB roll-off at 208 kHz

Sine wave 10 Hz and 100 Hz

Sine wave 1 kHz and 10 kHz

100 kHz and 1 MHz signals

Square wave 10 Hz and 100 Hz

Square wave 1 kHz and 10 kHz

60 W total power, 1 kHz symmetry cutoff

Thus, it becomes clear that a simple and high-quality design of UMZCH is not necessarily made using integrated circuits- only 8 transistors allow you to achieve decent sound with a circuit that can be assembled in half a day.

The editors of the “Two Schemes” website present a simple but high-quality low-frequency amplifier based on MOSFET transistors. His circuit should be well known to radio amateurs and audiophiles, since it is already about 20 years old. The circuit was developed by the famous Anthony Holton, which is why it is sometimes called ULF Holton. The sound amplification system has low harmonic distortion, not exceeding 0.1%, with a load power of about 100 watts.

This amplifier is an alternative to the popular amplifiers of the TDA series and similar pop ones, because at a slightly higher cost you can get an amplifier with clearly better characteristics.

The big advantage of the system is simple design and an output stage consisting of 2 inexpensive MOS transistors. The amplifier can work with speakers with impedance of both 4 and 8 ohms. The only adjustment that needs to be made during startup is to set the quiescent current value of the output transistors.

Schematic diagram of UMZCH Holton

Holton amplifier on MOSFET - circuit diagram

The circuit is a classic two-stage amplifier; it consists of a differential input amplifier and a symmetrical power amplifier, in which one pair of power transistors operates. The system diagram is shown above.

Printed circuit board

ULF printed circuit board - finished view

Here is the archive with PDF files printed circuit board - .

Amplifier operating principle

Transistors T4 (BC546) and T5 (BC546) operate in a differential amplifier configuration and are designed to be powered by a current source built on the basis of transistors T7 (BC546), T10 (BC546) and resistors R18 (22 kohm), R20 (680 Ohm) and R12 (22 rooms). The input signal is fed to two filters: a low-pass filter, built from elements R6 (470 Ohm) and C6 (1 nf) - it limits the high-frequency components of the signal and a bandpass filter, consisting of C5 (1 μF), R6 and R10 (47 kohm), limiting signal components at infra-low frequencies.

The load of the differential amplifier is resistors R2 (4.7 kΩ) and R3 (4.7 kΩ). Transistors T1 (MJE350) and T2 (MJE350) represent another gain stage, and its load is transistors T8 (MJE340), T9 (MJE340) and T6 (BD139).

Capacitors C3 (33 pf) and C4 (33 pf) counteract the excitation of the amplifier. Capacitor C8 (10 nf) connected in parallel with R13 (10 kom/1 V) improves the transient response of the ULF, which is important for rapidly rising input signals.

Transistor T6, together with elements R9 (4.7 ohms), R15 (680 Ohms), R16 (82 Ohms) and PR1 (5 ohms), allows you to set the correct polarity of the amplifier output stages at rest. Using a potentiometer, it is necessary to set the quiescent current of the output transistors within 90-110 mA, which corresponds to a voltage drop across R8 (0.22 Ohm/5 W) and R17 (0.22 Ohm/5 W) within 20-25 mV. The total current consumption in idle mode of the amplifier should be around 130 mA.

The output elements of the amplifier are MOSFETs T3 (IRFP240) and T11 (IRFP9240). These transistors are installed as a voltage follower with a large maximum output current, so the first 2 stages must drive a sufficiently large amplitude for the output signal.

Resistors R8 and R17 were used mainly for quickly measuring the quiescent current of power amplifier transistors without interfering with the circuit. They may also be useful in case of expanding the system with another pair of power transistors, due to differences in the resistance of the open channels of the transistors.

Resistors R5 (470 Ohm) and R19 (470 Ohm) limit the charging rate of the pass transistor capacitance, and, therefore, limit the frequency range of the amplifier. Diodes D1-D2 (BZX85-C12V) protect powerful transistors. With them, the voltage at startup relative to the power supplies of the transistors should not be more than 12 V.

The amplifier board provides space for power filter capacitors C2 (4700 µF/50 V) and C13 (4700 µF/50 V).

Homemade transistor ULF on MOSFET

The control is powered through an additional RC filter built on elements R1 (100 Ω/1 V), C1 (220 μF/50 V) and R23 (100 Ω/1 V) and C12 (220 μF/50 V).

Power supply for UMZCH

The amplifier circuit provides power that reaches a real 100 W (effective sine wave), with an input voltage of around 600 mV and a load resistance of 4 ohms.

Holton amplifier on a board with details

The recommended transformer is a 200 W toroid with a voltage of 2x24 V. After rectification and smoothing, you should get bipolar power supply to the power amplifiers in the region of +/-33 Volts. The design presented here is a mono amplifier module with very good parameters, built on MOSFET transistors, which can be used as a separate unit or as part of.

A low frequency amplifier (LF) is an integral part of most radio devices such as a TV, player, radio and various household appliances. Let's consider two simple circuits two-stage ULF on.

The first version of ULF on transistors

In the first version, the amplifier is built on silicon transistors n-p-n conductivity. The input signal comes through variable resistor R1, which in turn is the load resistance 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.

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 they are used in car radios, active subwoofers, home acoustics and in many other audio amplifiers and 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.