SU365017A1 - TWO-POWER POWER AMPLIFIER - Google Patents

Description

one

This invention relates to transistor power amplifiers.

This amplifier can be used in powerful output devices of radio equipment for various purposes.

A push-pull power amplifier is known, which contains an input stage on transistors of different types of conductivity, an output stage on transistors of one type of conductivity, and a control transistor.

The purpose of the invention is to increase the stability of the operation mode of the amplifier and protect the output transistors against overload. It is achieved by the fact that, in the proposed amplifier, the emitters of the input stage transistors are connected directly to the base transistor of the output stage connected to the common collector circuit, and the base of one of the input stage transistors is connected through a series-connected resistor to the collector of the control transistor.

The drawing is a schematic diagram of a push-pull power amplifier.

The amplifier contains an input type p / p transistor, a type 2 transistor, a type 3-4 output transistors, a control transistor 5, a signal source 6, a bias circuit 7 and 5, resistors 9 -16, capacitors 17-19; load 20, zener diodes 21 and 22.

The proposed push-pull audio power amplifier contains transistors / and 2 at the input stage, transistors at the output stage 4 4 W. control transistor 5. The base of the transistor / is connected to the signal source 6 and the bias circuit 7, the collector is connected to the power source pole

through the resistor 9. The emitter of the transistor / is connected to the emitter of transistor 2 and the base of the output transistor 3 directly, and to the base of transistor 2 through a capacitor 17 and a resistor 10. The common connection point of resistor 10 and capacitor 17 is connected via resistor // to the power supply pole . The base of transistor 2 is connected via resistors / 2 and 13 to the collector of control transistor 5, and through resistor 12 and capacitor 18 to the common emitter point of transistor 3 and collector of transistor 4. This same point is connected to load 20, and through capacitor 19 and resistor 14 - with the base of the control transistor. Manager Base

the transistor is connected via resistor 15 and offset value 8 to the power supply pole b, and through resistor 15 and zener diode 21 to the common connection point of the emitter of transistor 5, collector of transistor 3 and resistor 16. The latter is connected to power source pole with its other end. The collector of the transistor 2 is connected to the pole b of the power supply. The emitter and the base of the output transistor 4 are connected via a Zener diode 22 and a resistor 9 with a pole and a pit-5 source. The base of the transistor 4 is connected to the collector of the input transistor / directly. In the mode, the rest current through transistors 1-5 is set by the bias circuit 7-8, the sta-Yu bilitron 22 and resistors 16, 9, 10, and 11. The emitter current of transistor 5 is set by the bias circuit 7 and resistors 10 and 11, and the current through transistors / and 2 - zener diode 22, connected in the forward direction, and resi-15 by stator 9. At the same time, the current through resistors 10 vi 11 is set greater than the possible maximum return current of the collector of transistor 2. If the reverse current of the collector of transistor 2 is less than its base current resistors 20 10, 11 and capacitor 17 are optional. Due to the fact that all transistors are in the negative feedback feedback loop and the collector of control transistor 5 is connected directly to the base of transistor 2, the instability coefficient of the output current of the collector of transistor 4 is significantly less than one, the quiescent current of transistor 5 and 4 rigidly stabilized. For example, increasing the output30 of the collector current of transistor 3 causes a decrease in the emitter current and, accordingly, the collector current of transistor 5, thereby reducing the bias voltage at the emitter-base portion of transistor 2 and decreasing its emitter current and, accordingly, the collector current of the input transistor 1. This current, flowing through a resistor 9, reduces the bias voltage at the base-emitter section of the transistor 4. At the same time, the collector current of trans-40 resistor 3 decreases, and stabilization of the output collector current of this transducer is achieved. anzistor. In the dynamic mode, when the signal from the source 45 of signal 6 arrives at the base of the transistor /, in one half period of the input signal to the load 20, transistors 1 a 4 are working, ъ the other half period is transistors 1, 4, 2 n 3. The input signal to the transistor base -50 stor 2 comes from the output of the amplifier through a capacitor 18 and a resistor 12. Despite the large asymmetry of the amplifier's shoulders for current amplification for different half-periods of the input signal, nonlinear distortions 55 are quite small due to deep negative current and voltage feedback . In the half-life of the transistors / and 4, this connection is made through the emitter-base portion of transistor 3, which is not fully closed due to the fact that an additional signal from the amplifier output goes to the base of transistor 5 through a capacitor 19 and a resistor 14. In this case, the transistor 5 in the region of a large signal enters into saturation, and the current flowing through resistors 12 and 13 opens transistors 2 and 5. In the half-period of operation of transistors 1, 4, 2 and 3, transistors 1 and 4 first turn on the load. transistors are reduced; while the emitter currents of transistors 2 and 3 grow due to the fact that the signal from the amplifier output goes to the base of transistor 2 through capacitor 18 and resistor 12. The collector current of transistor 3 is closed through the zener diode 21 connected in the forward direction and low-impedance bias circuit 8, performed, for example, also on a zener diode. At the same time, the collector current of transistor 5 decreases and closes to the load through resistor 13 and capacitor 18. With the help of follower feedback capacitor 17 and resistor 10, the shunting effect of resistor 11 on the signal to the base of transistor 2 from the amplifier output is reduced. For this half cycle, the AC and voltage feedback is carried out via transistors /, respectively. The protection of the output transistors against overload is achieved by the fact that the AC signal at the output disappears at the moment of short circuit of the load. Therefore, alternating current is not supplied to the bases of transistor 2 and control transistor 5 through capacitors 18 and 19 and resistors 12 and 14, respectively, which protects output transistors 5 and 4. A decrease in short circuit current is achieved by connecting the collector of transistor 2 to a common point connection of the emitter and collector of the control and output transistors, The subject of the invention Push-pull power amplifier, containing an input stage on transistors of different types of conductivity, an output stage on transistors one conduction type, one of the transistors of which is connected according to a circuit with a common collector, and the other - according to a scheme with a common emitter, and a control transistor, characterized in that, in order to increase the stability of the amplifier operation mode and protect the output transistors from overload, the input transistors the cascade is connected directly to the base of the transistor of the output stage connected according to the circuit with a common collector, and the base of one of the transistors of the input stage is connected via two series-connected resistors to the collector py control transistor.