Cyclotron on two transistors. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Transistor power amplifiers

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The diagram below was created from many variations of this topology, based on the maximum sound quality.

Its advantages include the current control of the output transistor, the absence of the need for zero-balancing at the output, and the absolute symmetry of the signal amplification. The disadvantage is the dependence of the quiescent current on the load resistance. Adjusting the gain from minimum to maximum changes the quiescent current very little. The minimum volume level is made by the method of not connecting the first group of contacts. Thus, no quiescent current flows through the output transistor. It is better to connect the speaker as shown in the diagram, i.e. to nutritional benefits. In this version, microdynamics, accuracy and speed of working out subtle moments are better.

(click to enlarge)

The network transformer is made according to the same principle as in previous models. Transistors used MJL21194. Rectifier diodes 80SQ045. DC/DC converters in this amplifier TEN 30-2409WI by TRACO with an input voltage of 10 ... 40 V and an output voltage of 2,5 V (8A). They require two. The input transformer is made simply. A 113-meter-long bundle consisting of 21 strands is wound on the already existing nanoperm rings M-20 in size. Six cores of PETV 0,1 wire for the primary winding (three cores for one arm and three for the other). Two strands of PESHOK 0,12 wire for the first sections of the secondary windings (they are marked in light green) and twelve strands of PETV 0,315 wire for the remaining sections of the secondary windings. Sections consisting of wire PESHOK 0,12 have an active resistance of about 870 ohms each. Thus, they are current-setting. In this case, the quiescent current is 100-105 mA. The remaining sections of the secondary winding have an active resistance of approximately 3,8 ohms each.

In the process of designing, the following points of constructing this scheme were found out:

1. Two galvanically independent bias sources are needed.
2. Mandatory absence of any inter-emitter resistors.
3. The absence of any resistors in the circuit at all. Their role should be played by a current-setting winding with high internal resistance.
4. Connecting the load to the collectors.
5. The absence of any bindings to the ground and common wires.
6. The excitation signal must not pass through the speaker.
7. I still didn’t install thermal compensation, or rather removed it - it spoils the sound. After a long listening, it turned out that the amplifier practically does not heat up. You can, in extreme cases, use computer coolers with a soft-start fan, powered by a temperature sensor.
8. The places on the diagram where there are exclamation marks are very critical. From the emitters of the transistors, the excitation current must go first. Structurally, a thick wire (annealed copper monocore 2,0) is soldered directly to the transistor output spine, and the other end to the DC / DC converter. Further, a power circuit wire is soldered to the emitter terminal. This gives a clear and natural elaboration of ultra-quiet places. On the contrary, you can't do it. If possible, the conductors should be as short as possible.
9. Another important place: the conductors from the biscuit engine to the terminals of the bases of the transistors. They turned out to be about eight centimeters. Having tried many different options, I settled on a copper monocore with a diameter of 0,8. You don't need to burn it.

And I would say that this circuit is built on the principle of a current horn. Both in circuitry and in terms of conductors (here we mean the use of different diameters). Of course, neodymium magnets on transistors are also supplied. This contributes to the enlightenment of the sound, which is heard very clearly. The body is made in exactly the same way as the previous complementary version. The whole structure is made according to the descending principle. The lowest point is the output terminals. Why this is necessary, I think it is clear.

Well, the project is completed. If there is time and inspiration, then maybe something will come to mind. What is time? For myself, I gave the following definition: the amount of movement of changes in events (it’s too early to write about gravity yet). I will also say that this amplifier not only does not extinguish, but also enhances the informational nature of the electricity received from the bias source. In other words, it (amplifier) ​​can be used for medical purposes as well. This is in cases where the patient cannot take the medicine orally due to negative reactions of the body, and the basic properties of the medicine are required. That's when it is necessary to transfer the information structure of the substance into the electrical component with its further amplification. But I won't write about that either. In general, repeat the design and listen to your favorite works.

In the development of this scheme, and the addition of the above points, it is possible to formulate the fundamental principle of constructing a high-quality sound apparatus. It consists in the following: one and only one uniform current must flow through one single wire. It is highly desirable that it also does not change direction, but only amplitude. In this circuit, all places are executed according to this principle, with the exception of one: the internal base-emitter junction. In it, along this short segment of the conductor, two dissimilar currents flow, namely: the exciting circuit and the power circuit. This is where the task arises, which can be singled out as a separate study: "Opening a bipolar transistor in a non-galvanic way."

Author: George; Publication: cxem.net

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