SU416821A1 - - Google Patents

Description

one

This invention relates to radio engineering and, in particular, to low-frequency amplifiers.

Known low-frequency amplifiers containing the INPUT cascade, the pre-terminal cascade on the transistor, the collector of which is connected via a resistive divider to the load, and the output push-pull cascade performed on transistors of one type of conductivity, one of which is connected with a common collector, and the other with common emitter.

However, the known amplifiers have a large current.

The aim of the invention is to reduce the quiescent current of the amplifier.

For this, the emitter of the first transistor of the output stage is connected to the collector and the base of the second transistor of the output stage, respectively, through a resistor and an additional transistor of the opposite conductivity type, the base of which is connected to the IK resistive divider.

The drawing shows a circuit diagram of an amplifier.

The low-frequency amplifier contains a transistor 1 of an amplifier stage, a transistor 2 of a pre-terminal stage, a transistor 3 of an additional amplifier stage, a transistor 4, 5 of the terminal stage, a resistor 6 and a dynamic loudspeaker 7.

The amplifier works as follows.

The signal amplified by transistor 1 is fed to the base of transistor 2 of the pre-terminal cascade, which operates in alternating mode: in class A mode for a negative (positive) half-wave signal, and in class AB mode with a low initial current for a positive half-wave (negative). Cascades on transistors 3, 4, 5 operate in class B mode.

For a negative (positive) half-wave of the signal amplified by transistor 4, the load is a dynamic loudspeaker 7, and for a positive half-wave signal amplified by transistors 3 and

5 is a circuit consisting of a dynamic loudspeaker 7 and a resistor 6.

Thus, the negative feedback voltage taken from successively

included 6 n dynamic loudspeaker 7, will be more for a positive (negative) half-wave signal amplified by transistors 3 and 5. This allows you to fully compensate

the difference in gains between cascades on transistors 3 and 5 and transistor 4. Resistor 6 serves to reduce nonlinear distortion and is chosen so that the amplifier does not reflect the output power.

Subject invention

Low-frequency amplifier, -containing input: a kaokad, a pedestal cascade on a transistor whose collector is connected to a load through a resistive divider, and an output push-pull cascade implemented on transistors of the same type of conductivity, one of which is included in the circuit with a common

a collector, and another with a common emitter, characterized in that, in order to reduce the quiescent amplifier current, the emitter of the first of the output transistors of the aocad is connected to the collector and base of the second transistor of the output stage, respectively, through an additional transistor of opposite type and conductivity, the base of which is connected to resistive divider.

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