Linear transistor KB amplifier with a power of 50 watts. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / RF power amplifiers

 Comments on the article

The IRF520 linear power amplifier based on field-effect transistors, developed by the Polish radio amateur Jerzy Mroszczak (SQ7JHM), differs from most of the technical solutions known nearby, although not new, but rather rarely used. Its good parameters and high signal quality are confirmed by a large number of positive feedback received from correspondents in QSOs conducted by the author.

Fig. 1

The appearance of the amplifier is shown in fig. 1, and its diagram is in Fig. 2. The amplified signal applied to the XW1 connector enters through an attenuator of resistors R1-R3 and a transformer T1 to the gates of field-effect transistors VT1 and VT2. The scheme used provides good symmetry of the gate signals. With the help of a tuning resistor R7, a constant bias is set on the gates of the transistors, which provides a quiescent current in the circuit of their drains (in the absence of an alternating voltage at the gates) of about 80 ... 100 mA. The total quiescent current, which can be measured by connecting the ammeter to the break in the power wire marked in the diagram with a cross, is twice as much - 160 ... 200 mA. At maximum output power, the current here increases to approximately 4 A.

Fig. 2

The resistive attenuator serves to better match the amplifier with the signal source and dampen the excess power of this signal. The values ​​of the resistors R1-R3 indicated in the diagram are optimal when working from the Kajman transceiver used by the QRP author with an output power of 2 watts. In other cases, these resistors may have to be re-selected. Transformer T1 is wound with double-folded insulated copper wire with a diameter of 0,55 mm on a ring ferrite magnetic circuit FT-82-43. Its windings contain 11 turns.

The amplifier uses an original unit for summing the output signals of the arms of a push-pull amplifier, assembled on a T2 transformer, which also serves to match the amplifier with a 50-ohm load. Isolating capacitors C6-C9 do not allow the DC component of the transistor drain current to pass into the transformer windings. This saves its magnetic circuit from unwanted bias, which may result in increased non-linear distortion of the output signal, insufficient power, and an increased level of harmonics at the output. The design and number of turns of the windings of the transformer T2 are the same as those of T1. But its magnetic circuit is glued from two ferrite rings FT-114-43, and the diameter of the winding wire is 1 mm.

It is impossible to get rid of the DC component of the current flowing in the windings of the inductors L1, L2, L4, L5. The danger of saturation is eliminated here in a different way - by using open rod rather than closed ring magnetic circuits. Chokes L1 and L2 have 25 turns of wire 1 mm in diameter, wound on a ferrite rod with a diameter of 8 mm, and chokes L4 and L5 - 20 turns of the same wire on a rod 5 mm in diameter. The author, unfortunately, does not report the magnetic permeability of ferrite rods, saying only that it should be high.

Coil L3 is wound on an annular magnetic circuit T68-2 made of carbonyl iron. It contains 19 turns of wire with a diameter of 0,9 mm.

The printed circuit board of the amplifier is shown in fig. 3. The foil on its reverse side is completely preserved. With several wire jumpers passed through specially drilled holes, it is connected to a common printed conductor on the front side. Windows are made for the cases of field-effect transistors in the board, and the transistors themselves are mounted on heat sinks. Transistors must be selected with a parameter spread of no more than 10%. If this fails, shown in Fig. 3 wire jumpers in the source circuits of the transistors must be replaced with resistors with a resistance of 0,22 ohms and a power of 2 watts.

Fig. 3

When a sinusoidal signal with an amplitude of 9 V was applied to the input of the amplifier, a power of 50 W was obtained at its load of 55 Ohms. According to the author, it depends little on the frequency in the entire KB range, which, unfortunately, he does not indicate the boundaries of and the magnitude of the unevenness.

Publication: radioradar.net

See other articles Section RF power amplifiers.

Read and write useful comments on this article.

<< Back

Latest news of science and technology, new electronics:

Artificial leather for touch emulation 15.04.2024

In a modern technology world where distance is becoming increasingly commonplace, maintaining connection and a sense of closeness is important. Recent developments in artificial skin by German scientists from Saarland University represent a new era in virtual interactions. German researchers from Saarland University have developed ultra-thin films that can transmit the sensation of touch over a distance. This cutting-edge technology provides new opportunities for virtual communication, especially for those who find themselves far from their loved ones. The ultra-thin films developed by the researchers, just 50 micrometers thick, can be integrated into textiles and worn like a second skin. These films act as sensors that recognize tactile signals from mom or dad, and as actuators that transmit these movements to the baby. Parents' touch to the fabric activates sensors that react to pressure and deform the ultra-thin film. This ... >>

Petgugu Global cat litter 15.04.2024

Taking care of pets can often be a challenge, especially when it comes to keeping your home clean. A new interesting solution from the Petgugu Global startup has been presented, which will make life easier for cat owners and help them keep their home perfectly clean and tidy. Startup Petgugu Global has unveiled a unique cat toilet that can automatically flush feces, keeping your home clean and fresh. This innovative device is equipped with various smart sensors that monitor your pet's toilet activity and activate to automatically clean after use. The device connects to the sewer system and ensures efficient waste removal without the need for intervention from the owner. Additionally, the toilet has a large flushable storage capacity, making it ideal for multi-cat households. The Petgugu cat litter bowl is designed for use with water-soluble litters and offers a range of additional ... >>

The attractiveness of caring men 14.04.2024

The stereotype that women prefer "bad boys" has long been widespread. However, recent research conducted by British scientists from Monash University offers a new perspective on this issue. They looked at how women responded to men's emotional responsibility and willingness to help others. The study's findings could change our understanding of what makes men attractive to women. A study conducted by scientists from Monash University leads to new findings about men's attractiveness to women. In the experiment, women were shown photographs of men with brief stories about their behavior in various situations, including their reaction to an encounter with a homeless person. Some of the men ignored the homeless man, while others helped him, such as buying him food. A study found that men who showed empathy and kindness were more attractive to women compared to men who showed empathy and kindness. ... >>

Random news from the Archive New Year's Eve comes a second later 31.12.2016 The last day of 2016 will last a second longer. This will be confirmed by the computer clock, which, before the onset of January 1, will show an unusual value of 23:59:60. The extra second will help bridge the gap between international coordinated time. The leap second will appear before midnight on December 31, when the whole world will celebrate the new year 2017. Day extension is related to International Time Coordination (UTC). The gap appears during the daily rotation of the Earth and is measured by atomic clocks and UT1, but it needs to be reduced periodically. Adding an extra second has already happened 26 times. The first time such a procedure was carried out occurred on June 30, 1972, and the last time on June 30, 2015.

Other interesting news:

▪ Magic Leap 1 Mixed Reality Headset

▪ Sony Handycam FDR-AX4E 1K camcorder

▪ Processing moon dust into oxygen

▪ The latest solar panels for spacecraft

▪ Dinosaurs time to cut

News feed of science and technology, new electronics

Interesting materials of the Free Technical Library:

▪ section of the Radio Control website. Article selection

▪ Molotov cocktail article. Popular expression

▪ article How did lunar craters form? Detailed answer

▪ article The driver of the car with the installed removable equipment of the sand and salt spreader. Standard instruction on labor protection

▪ article LED rechargeable flashlight. Encyclopedia of radio electronics and electrical engineering

▪ article Stabilized power supply, 60 volts 0,1 amperes. Encyclopedia of radio electronics and electrical engineering

Leave your comment on this article:

All languages ​​of this page

Arabic	Hebrew	Polish
Bengali	Hindi	Portuguese
Chinese	Italian	Spanish
English	Japanese	Turkish
French	Korean	Ukrainian
German	Malay	Vietnamese

Home page | Library | Articles | Website map | Site Reviews

www.diagram.com.ua
2000-2024