RU2601182C1 - Two-cycle power amplifier - Google Patents

Abstract

FIELD: radio electronics.

SUBSTANCE: invention relates to radio electronics and can be used as an amplifier of high power sinusoidal oscillations. In power amplifier with transformer input and output, each arm of which is made on transistor with resistor in emitter, second outputs of resistors in emitters of both arms are connected to common point of the circuit. Collectors are connected to extreme connections of the primary winding of the output transformer, load is connected to its secondary winding. power supply source is connected between middle point of the primary winding of the output transformer and the common point of the circuit. Input signal source is connected to the primary winding of the input transformer. Two additional resistors are included in amplifier circuit. First additional resistor is connected between the first output of the secondary winding of the input transformer and first transistor base, and connection point of first additional resistor and first transistor base is connected to second transistor emitter. Second additional resistor is connected between the second output of the secondary winding of the input transformer and second transistor base, and connection point of second additional resistor and second transistor base is connected to first transistor emitter.

EFFECT: separation of functions of limitation of reverse voltage and control of output power.

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Description

The invention relates to the field of electronics and can be used as an amplifier of sinusoidal oscillations of increased power.

Known push-pull power amplifier [1] with transformer input and output, containing two transistors, the emitters of which are connected to a common point of the circuit, the bases of both transistors are connected to a common point of the circuit through resistors, collectors of transistors are connected to the extreme terminals of the primary winding of the output transformer, between the midpoint the primary winding and the common point of the circuit includes a power source, the load is connected to the secondary winding of the output transformer, the terminals of the secondary winding of the input transformer respectively They are connected to transistor bases, and the source of the amplified signal is connected to the primary winding of the input transformer.

Since power amplifiers work with large input signals, very often the reverse voltage between the base and the emitter of transistors in such an amplifier exceeds the value allowed by the technical conditions.

The closest in technical essence to the claimed technical solution is a push-pull power amplifier [2] with a transformer input and output, each arm of which is made on a transistor with a resistor in the emitter circuit, the transistor base being connected to one end of the corresponding secondary winding of the input transformer, the other end of each the secondary winding of the input transformer is connected to the emitter of the transistor of the opposite arm.

In such an amplifier, the magnitude of the reverse voltage between the base and the emitter of the transistor is determined by the difference between the magnitude of the voltage on the secondary winding of the input transformer and the magnitude of the voltage across the resistor in the emitter circuit of the open transistor. Thus, in the known device, the resistor in the emitter circuit, while reducing the reverse voltage value of the closed transistor, simultaneously reduces the gain of the amplifier.

The technical result of the present invention is the separation of the functions of limiting the reverse voltage and regulating the output power of the amplifier.

The technical result is achieved in that in a push-pull power amplifier with a transformer input and output, each arm of which is made on a transistor with a resistor in the emitter, the second terminals of the resistors in the emitters of the transistors of both arms are connected to a common point in the circuit, the collectors of the transistors are connected to the extreme terminals of the primary output winding a transformer, to the secondary winding of which a load is connected, between the midpoint of the primary winding of the output transformer and the common point of the circuit is connected and the source of the amplified signal is connected to the primary winding of the input transformer, two additional resistors are introduced into the amplifier circuit, the first additional resistor connected between the first terminal of the secondary winding of the input transformer and the base of the first transistor and the connection point of the first additional resistor and the base of the first transistor is connected to the emitter of the second transistor, and a second additional resistor is connected between the second terminal of the secondary winding of the input transformer and the base of the second transistor pa and the connection point of the second additional resistor and the base of the second transistor is connected to the emitter of the first transistor.

In FIG. 1 is a diagram of a push-pull power amplifier. A push-pull power amplifier contains an amplified signal source 1, an input transformer 2, a first transistor 3 with a resistor 4 in the emitter circuit, a second transistor 5 with a resistor 6 in the emitter circuit, a first additional resistor 7, a second additional resistor 8, an output transformer 9, a load of 10, and power source 11.

In FIG. 2 presents the results of modeling the operation of a push-pull power amplifier. In FIG. 2 numbers indicate: 12 - the output signal of the source 1, 13 - the signal between the base and the emitter of the first transistor 3, 14 - the signal between the base and the emitter of the second transistor 5, 15 - the signal on the collector of the first transistor 3, 16 - the signal on the collector of the second transistor 5 , 17 - output signal of the amplifier.

Push-pull power amplifier operates as follows. The bipolar sinusoidal signal from source 1 through the output winding of transformer 2 and resistors 7 and 8 is supplied to the bases of the first 3 and second 5 transistors, respectively, connected to the emitters of the second 5 and first 3 transistors, respectively. Thus, between the base and emitter of the first transistor 3 and the base and emitter of the second transistor 5, alternating voltage is applied alternately after half the period of the initial signal, while the base-emitter transitions of each of the transistors 3, 5 in combination with resistors 7, 8 work as a semiconductor voltage limiter. Limiting the magnitude of the reverse voltage at the base-emitter junctions of each transistor is achieved by the fact that the junctions are turned on in the opposite direction and the forward (opening) voltage of one transistor will be reverse for the other. Thus, the magnitude of the reverse voltage at each transistor never exceeds the forward voltage. The waveform between the bases and emitters of transistors 3 and 5 is shown in FIG. 2 under numbers 13 and 14 respectively.

Transistors 3 and 5 open alternately after half the period and the current from the source 11 flows alternately through each half of the primary winding of the output transformer 9 and the corresponding resistor 4 or 6. The antiphase currents of the primary winding are added to the secondary winding of the output transformer and enter the load 10. By changing the value of the resistors 4 and 6 in the emitters of transistors is regulated by the output power of the amplifier.

In FIG. 2 shows the ratio of the amplitudes and frequencies of the input 12 and output 17 signals of the proposed power amplifier. The amplitude of the sinusoidal signal of source 1 is 5 V, the frequency is 5 MHz. The transformation coefficient of the input transformer 2 by voltage is 2. The value of the additional resistors 7, 8 is 0.5 Ohms. The value of resistors 4, 6 in the emitters of transistors is 2 ohms. The transformation ratio of the output transformer 9 by voltage is 10. The load resistance 10 is 50 Ohms. The voltage of the power source 11 is 28 V.

INFORMATION SOURCES

1. Design of radio transmitting devices. Textbook for universities edited by VV Shahgildyan, Moscow: Radio and Communications, 1993, p. 107, fig. 2.11b.

2. USSR Author's Certificate No. 507912, 25.03.76. Push-pull power amplifier.

Claims (1)

A push-pull power amplifier with a transformer input and output, each arm of which is made on a transistor with a resistor in the emitter, the second terminals of the resistors in the emitters of the transistors of both arms are connected to a common point in the circuit, the transistor collectors are connected to the extreme terminals of the primary winding of the output transformer, to the secondary winding of which load, between the midpoint of the primary winding of the output transformer and the common point of the circuit, a power source is connected, to the primary winding of the input transformer an amplified signal source is connected, characterized in that two additional resistors are introduced into the push-pull amplifier circuit, the first additional resistor connected between the first terminal of the secondary winding of the input transformer and the base of the first transistor, and the connection point of the first additional resistor and the base of the first transistor connected to the emitter of the second transistor, and the second additional resistor is connected between the second terminal of the secondary winding of the input transformer and the base of the second transistor and point c The connection of the second additional resistor and the base of the second transistor is connected to the emitter of the first transistor.

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