SU543134A1 - Amplifier - Google Patents

Description

as well as a low-impedance bias source 11 and a resistor 12 connected to the power supply bus 13.

The power amplifier works as follows.

In the current mode, the current through the input and output transistors 1 and 2 is determined by the magnitude of the resistance of the resistor 12 and the voltage on the base-emitter section of the output transistor 3, the quiescent current of which is determined by the resistance of the resistors 6-8 and not the bias connected to the input of the amplifier. The additional transistor 10 in the quiescent mode is closed, since the voltage of the bias source 11 and the voltage drop across the resistor 8 are appropriately selected. The mode of operation of the transistors 1–3 by direct current is stabilized by the deep negative feedback surrounding the amplifier.

The device is a push-pull unbalanced power amplifier, the output transistors 2 and 3 of which operate in class AB. In dynamic mode, the amplifier works differently with negative and positive half-wave signals.

With a negative half-wave signal on the amplifier's input, transistors 1 and 3 take part in its operation, while transistors 2 and 10 are closed. The load through the Zener diode 4 operates the output transistor 3.

When the input signal has a negative half-wave, the output transistor 2 operates, and the output transistor 3 performs the role of a Class A pre-final stage providing the necessary input current for the output stage assembled on transistors 2 and 10. An additional transistor 10 closes the positive feedback circuit, covering the output stage. Due to the effect of this connection to the base of the output transistor 2 from the amplifier output through the capacitor 5, the resistor 7 and the emitter-collector gap of the additional transistor

10, an additional current is supplied, the amplitude of which is determined by the amplitude of the voltage of the signal at the amplifier output and by the magnitude of the resistor 7. As a result of the positive coupling, the current amplitude required by the output transistor 3 decreases, which allows for a corresponding decrease in the rest current and the power dissipated by the output transistor 3 .

The nonlinear distortions introduced by the amplifier are quite small, since it is a repeater with a voltage gain close to one and is covered by a very deep negative

feedback.

Since the auxiliary transistor 10 is closed at the moment of switching on the power supply voltage, the current pulse through the output transistor 2 has a small amplitude with an appropriate choice of resistors 6, 7 and 8.

Claims (1)

Invention Formula A power amplifier containing an input transistor connected in series along the power supply circuit with the first output transistor, and a second output transistor, the base of which is connected to the collector of the input transistor, while the junction of the emitters of the input and nerve output transistors is connected to the junction of the base of the first and second output collectors transistors through the Zener diode and simultaneously through the capacitor, to the removal of a resistive divider, one end connected to the base of the first output transistor, is different In order to reduce the power dissipation, the second end of the resistive divider through the newly introduced resistor is connected to the corresponding power supply bus, and through an additional transistor connected on the common base circuit to the base of the first output transistor.