SU1506512A1 - Power amplifier - Google Patents

Abstract

The invention relates to amplifier technology. The purpose of the invention is to increase the speed at high output currents. The power amplifier contains transistors (T) 1-6, sources 7 and 8 current and resistors 9-12. In this amplifier, the input capacitance is reduced by an amount close to the sum of the collector-base capacitors T 1 and 2 of the input stage. This occurs due to the fact that the output voltage differs little from the input one and the process of recharging the indicated capacitances is practically absent. This reduces the time constant of the input circuit of the power amplifier, which increases its speed — the maximum rate of rise of the output voltage, and also broadens the passband. 1 il.

Description

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ten

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thirty

The invention is intended to be used in the output stages of an amplifier of audio and ultrasonic frequency signals, radio electronic devices for various purposes, in particular, in measuring equipment and amplifying equipment of high quality reproduction.

The purpose of the invention is to increase the speed at high output currents.

The drawing shows a circuit diagram of a power amplifier.

The power amplifier contains the first 1, second 2, third 3, fourth A, fifth 5 and sixth 6 transistors, first 7 and second 8 current sources, first 9, second 10, third 11 and fourth 12 resistors.

The power amplifier works as follows.

When the input signal has a positive half-wave, the current of the first source 7 is redistributed between the emitter circuit of the first transistor 1 and the base circuit of the third transistor 3, which leads to an increase in the collector current of the third transistor 3 and the fifth transistor 5 to the maximum value. In the negative half-period, similar processes occur in the lower arm of the circuit, consisting of the second source 8, as well as the second 2, fourth 4, and second 6 transistors. As a result, an output signal appears at the output, the amplitude of the current of which exceeds the amplitude of the input by a number of times, approximately equal to the product of the current gain in the circuit with a common emitter of transistors operating in one arm, with the amplitude of the voltage at the output of the amplifier, approximately equal to input.

The proposed implementation of the power amplifier allows you to expand the bandwidth and improve performance, since the input capacitance of the amplifier decreases by an amount close to the sum of the collector capacitances — the base of the first 1 and second 2 transistors, of the input stage, because the output voltage differs little from input and the process of recharging these tanks is practically absent, and thus causes, oo, a decrease in the constant time

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five

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five

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five

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five

the input circuit of the power amplifier, which increases the maximum rate of rise of the output voltage of the power amplifier (increase in speed), and also expands the bandwidth.

With an appropriate choice of the resistances of the first 9 and second 10 resistors, the effect of the load on the collector voltage — the base of the first 1 and second 2 transistors can be ignored in the calculation. So, for example, having received the resistance values of the first 9 and second 10 resistors 20 times as large as the resistance of the third 11 and fourth 12 resistors, it is obtained that the main part of the current in the load is provided by the fifth 5 and sixth 6 transistors, and the role of the third 3 and fourth 4 transistors are reduced only to supplying current to the collector circuits of the first 1 and second 2 transistors.

Claims (1)

Invention Formula A power amplifier containing the first and second transistors of different structure, the bases of which are combined and are the input of the power amplifier, and the emitter circuits include the first and second current sources, respectively, the third and fourth transistors of different structure, connected according to the circuit with a common collector, base which are connected to the emitters of the first and second transistors, respectively, and the emitters through the first and second resistors connected in series with each other, the common point of the resistors being the output of the power amplifier Spikes, characterized in that, in order to increase speed at high output currents, the collectors of the first and second transistors are connected to the emitters of the fourth and third transistors, respectively, the fifth and sixth transistors connected according to the common collector circuit, the bases of which are connected to bases of the third and the fourth transistors, respectively, and the emitters through the third and fourth resistors in series connected with each other, with their common point connected to the common point of the first and second resist oops.