Refinement of the UMZCH with a non-standard inclusion of an op-amp. Scheme, description

Free technical library

ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
Free library / Schemes of radio-electronic and electrical devices

Refinement of the UMZCH with a non-standard inclusion of an op-amp. Encyclopedia of radio electronics and electrical engineering

Free technical library

Encyclopedia of radio electronics and electrical engineering / Transistor power amplifiers

Comments on the article

At one time, many radio amateurs repeated the AF power amplifier described by N. Troshin in the article "UMZCH with non-standard inclusion of an op-amp" ("Radio". 1988. No. 6. p. 55, 56). According to radio amateurs, the amplifier is simple, reliable in operation, easy to set up and has very good parameters. All this is so. However, it also has a small drawback. The thing is. that at low volume levels, the sound of a loudspeaker working with this amplifier loses transparency and is noticeably distorted, especially when playing the signals of acoustic instruments.

These distortions appear due to the low quiescent current of the output transistors.

Small changes in the circuit diagram of the amplifier in question made it possible to increase the quiescent current of the output transistors, to make it more stable and independent of temperature. For this purpose, diodes VD3-VD6 and resistor R7 were excluded from the amplifier circuit, and instead a complementary pair of low-power transistors VTT' and VT2' (see figure) was introduced, which stabilizes the current through transistors VT2, VT3 and resistor R10. As a result, the quiescent current through the transistors VT4 and VT5 is also stabilized due to the resistors R11, R12 included in their emitter circuits.

Refinement of UMZCH with non-standard inclusion of OU

One of the newly introduced transistors VT' must have thermal contact with the output transistors. The easiest way for this purpose is to solder it at the terminals of these transistors. For example, the output of the base of the transistor VT1' can be soldered directly to the output of the base of the transistor VT4, and the outputs of its collector and emitter can be connected with thin mounting wires, respectively, to the base of the transistor VT2 and the emitter VT2'.

The other transistor VT2' should not have thermal contact with the UMZCH output transistors. To minimize the length of the connecting conductors, it should be installed on an additional getinax plate next to the specified transistors.

You can increase the stability of the UMZCH by connecting the circuit R1' and C1' to its output. The quiescent current of the output transistors is automatically set within 120...150 mA. UMZCH does not need additional adjustment.

When improving the stereo version of the UMZCH, it is useful to first refine one of the channels and. only after evaluating the sound quality, take up the revision of the second.

Author: M. Sapozhnikov, Ganei Aviv, Israel

See other articles Section Transistor power amplifiers.

Read and write useful comments on this article.

<< Back

Latest news of science and technology, new electronics:

Machine for thinning flowers in gardens 02.05.2024

In modern agriculture, technological progress is developing aimed at increasing the efficiency of plant care processes. The innovative Florix flower thinning machine was presented in Italy, designed to optimize the harvesting stage. This tool is equipped with mobile arms, allowing it to be easily adapted to the needs of the garden. The operator can adjust the speed of the thin wires by controlling them from the tractor cab using a joystick. This approach significantly increases the efficiency of the flower thinning process, providing the possibility of individual adjustment to the specific conditions of the garden, as well as the variety and type of fruit grown in it. After testing the Florix machine for two years on various types of fruit, the results were very encouraging. Farmers such as Filiberto Montanari, who has used a Florix machine for several years, have reported a significant reduction in the time and labor required to thin flowers. ... >>

Advanced Infrared Microscope 02.05.2024

Microscopes play an important role in scientific research, allowing scientists to delve into structures and processes invisible to the eye. However, various microscopy methods have their limitations, and among them was the limitation of resolution when using the infrared range. But the latest achievements of Japanese researchers from the University of Tokyo open up new prospects for studying the microworld. Scientists from the University of Tokyo have unveiled a new microscope that will revolutionize the capabilities of infrared microscopy. This advanced instrument allows you to see the internal structures of living bacteria with amazing clarity on the nanometer scale. Typically, mid-infrared microscopes are limited by low resolution, but the latest development from Japanese researchers overcomes these limitations. According to scientists, the developed microscope allows creating images with a resolution of up to 120 nanometers, which is 30 times higher than the resolution of traditional microscopes. ... >>

Air trap for insects 01.05.2024

Agriculture is one of the key sectors of the economy, and pest control is an integral part of this process. A team of scientists from the Indian Council of Agricultural Research-Central Potato Research Institute (ICAR-CPRI), Shimla, has come up with an innovative solution to this problem - a wind-powered insect air trap. This device addresses the shortcomings of traditional pest control methods by providing real-time insect population data. The trap is powered entirely by wind energy, making it an environmentally friendly solution that requires no power. Its unique design allows monitoring of both harmful and beneficial insects, providing a complete overview of the population in any agricultural area. “By assessing target pests at the right time, we can take necessary measures to control both pests and diseases,” says Kapil ... >>

Random news from the Archive

Gen8 generation IGBTs from IR for benchmark efficiency and reliability 27.04.2015

International Rectifier has released a series of IGBTs in the manufacture of which the new generation technology - Gen8 was used. The new transistors use the latest "Field-stop trench" IGBT chip technology and are rated for 1200V. The transistors are available in industry standard TO-247 packages.

The new transistors cover an operating current range from 8A to 60A, have a typical Vce(on)=1,7V, and a safe short-circuit operating area (SCSOA) of up to 10µs. All this allows to reduce heat losses, increase the output power density and ensure high reliability of industrial systems.

The new technology minimizes the dv/dt voltage slope, reducing EMI and lowering surge levels, making the Gen8 IGBT an ideal solution for motor drive applications. The switching frequency of these transistors is from 0 to 8 kHz (fast speed range).

The advent of this new technology and state-of-the-art silicon IGBT fabrication platform is the result of IR's efforts to advance technology in power electronics over several decades.

The company's goal is to achieve 100% of the possibility of using its components in inverters to control electric motors of various capacities in order to more efficiently use electrical energy and improve the environment.

Other interesting news:

▪ Worm blood transfusion to human

▪ 5000 tons of extraterrestrial particles fall to Earth every year

▪ Mobile workstation Eurocom Racer 3W

▪ Radeon RX 640 graphics card

▪ Global flood delayed

News feed of science and technology, new electronics

Interesting materials of the Free Technical Library:

▪ site section Welding equipment. Article selection

▪ article Linguistic concept of Saussure. History and essence of scientific discovery

▪ article Why do female squirrels collect the feces of their young with their mouths? Detailed answer

▪ article Lemon mint. Legends, cultivation, methods of application