Class B amplifier. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Transistor power amplifiers

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We offer you a class amplifier В with the following characteristics:

scheme

Extreme reduction of non-linear distortion was achieved by controlling the transistors of the output stage not by voltage, but by current. That is, transistors VT1 and VT2 are current sources for VT3 and VT4.

Without going into deep details, I will only say that this amplifier was assembled and worked without any tuning for a very long time, until some irresponsible citizens splashed beer on the radiators of the output transistors. For some reason they didn't like it.

Nevertheless, I want to give the tuning method for this amplifier, described by the author of the circuit.

To begin with, without load, by selecting resistors R7 and R8, a voltage of 1-2 volts is set on the bases of transistors VT0,4 and VT0,5. Then, resistor R5 sets zero voltage at the output of the amplifier. After that, the load is connected and listens to what happened from all this.

The amplifier is not critical to the choice of elements and does not require the selection of transistors. The operational amplifier K140UD8A can be replaced with K574UD1 or K544UD2. The output stage transistors are mounted on a radiator with an area of ​​at least 600 square meters. see And transistors VT1 and VT2 on separate radiators of 60 square meters. cm.

Publication: radiokot.ru

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