SU1741252A1 - Push-pull amplifier - Google Patents

Abstract

The invention relates to amplifier technology and can be used in the output stages of operational amplifiers, in power amplifiers. The purpose of the invention is improving speed. The emitters of the two pairs of additional transistors are the input to the amplifiers, to which a signal is supplied from the previous amplifying stage. Under the influence of the input signal, the ratio of the currents in the collector circuits of the additional transistors, creating a dynamic load to each other, changes. The amplified signal through the current-generating element and matching elements is supplied to the bases of transistors of push-pull stages. Further, this signal, amplified in power, is fed to the load circuit. 1 Il.

Description

The invention relates to amplifier technology and can be used in the output stages of operational amplifiers, as well as in power amplifiers.

The purpose of the invention is to increase speed.

The drawing shows a circuit diagram of a push-pull amplifier.

The push-pull amplifier contains 1 input and 2 output push-pull stages, each of which is performed on the first and second transistors having a different structure, the first 3 and second 4 resistors, the current supply element 5, two matching elements 6 and 7, the two first additional transistors 8 and 9 , two second additional transistors 10 and 11, inputs 12 and 13 for supplying the first and second reference voltages.

Push-pull amplifier works as follows.

The emitters of the two first 8 and 9 and two second 10 and 11 additional transistors are push-pull amplifier inputs, which receive a signal from a previous amplifier stage, made, for example, in the form of a dynamic stage amplifier.

At zero input signal, the push-pull amplifier is in balance, the collector current of transistor 8 of the input stage 1 is equal to the collector current of transistor 10 of the input stage 1, the collector current of transistor 9 of the output stage 2 is equal to the collector current of transistor 11 of the output stage 2, the currents of both transistors of the input 1 and output 2 stages are equal, the signal at the output of the amplifier is zero.

When a signal amplifier, for example, positive, arrives at the input, currents through transistors 8 and 9 increase, and currents of transistors 10 and 11 decrease. Collectors

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transistors 8.9 and 10.11 create mutually dynamic loads, so the potentials of the bases and, accordingly, the emitters of the first and second transistors of the push-pull stages 1 and 2 are shifted towards increasing their potential, the signal and voltage are amplified. With an increase in the amplitude of the input signal, the difference in the collector currents of the corresponding transistor pairs 8.9 and 10.11 increases, this difference in currents increases the excitation current of two-stroke stages 1 and 2, and the excitation current is greater, the greater the amplitude of the input signal. An increase in the excitation current makes it possible to increase the recharge rate of the parasitic capacitances of the base circuit of the first and second transistors, first of all, the base – collector capacitance, and also the collector capacitance – substrate of the current supply element 5 and matching elements 6 and 7 when the amplifier is integrated; signal at the output, especially at large signal amplitudes and, as a result, increase the speed of the amplifier.

High performance in the proposed push-pull amplifier is achieved by controlled current generators on resistors 3 and 4 and transistors 8-11, which allow creating large currents of overcharging and parasitic capacitances of push-pull stages.

The use of a push-pull amplifier, for example, as part of an operational amplifier, makes it possible to increase the cut-off frequency of the amplifier by 1.5–2 times, especially in large signal mode.

Claims (1)

Invention Formula Push-pull amplifier containing input and output push-pull stages, 0 five 0 five 0 five 0 each of which is made on the first and second transistors, having a different structure, connected according to a common collector circuit, as well as the first and second resistors, the first terminals of which are connected to the corresponding power terminals of a push-pull amplifier, while between the bases of the first and second transistors of the input push-pull cascade the current supply element is turned on, and between the bases of the first and second transistors of the output push-pull stage there are two series-connected matching elements, the junction points of which are Connected to the emitters of the first and second transistors of the input push-pull cascade, characterized in that, in order to improve performance, the first two additional transistors are introduced, having one structure, the bases of which are connected and are the input for supplying the first reference voltage, the emitters are connected to the second output the first resistor and are the first input bus of the push-pull amplifier, and the collectors are connected to the bases of the first transistors of the input and output push-pull stages, respectively, and two watts are introduced Additional transistors having a different structure, the bases of which are connected and are the input for supplying the second reference voltage, the emitters are connected to the second output of the second resistor and are the second input bus of the push-pull amplifier, and the collectors are connected to the bases of the second transistors respectively the input and output two-stroke cascades. -