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Сообщение: [QUOTE="Samodelkin, post: 366963, member: 1786"] Задача была поставлена, она выполнена: The dissipation of the output transistors is normally about 8W, and the output pair can both be mounted on a single 3.5in. x 4in. black anodised, ribbed heat sink. The heat sink should be earthed - very simply by omitting the mica washer on the MJ491 Статью в оригинале можно прочесть, там это уже есть: The classic system for output transistor protection, using two input bypass transistors, is that due to Bailey(3), and this is also applicable to the output circuit of this design. However, because of the d.c. asymmetry between the potential at the base of Tr3 and the output point 'X', a much simpler arrangement can be used, consisting solely of a good quality (low leakage) zener diode between these two points, with the positive zener end connected to the base of Tr3. Any 4 - 4.7V zener will do provided that the leakage current at 3V reverse, and 0.4V forward, is less than 10uA. The ITT400mW series ZF4.7 is quite suitable. Again, for 20W output into 8ohm, the resistors R1 and R2 must be reduced to 0.47ohm. [/QUOTE]