SU1569943A1 - Power amplifier - Google Patents

Abstract

The invention relates to radio engineering. The purpose of the invention is to expand the dynamic range. When a signal is applied to the input of a power amplifier, such as a positive polarity, the first transistor 1 starts to close and the fraction of the current of the first current source 7 flowing into the base of the third transistor 3 increases. A decrease in the emitter current of the first transistor 1 is associated with a decrease in the voltage on its base-emitter junction and an increase in the opening voltage on the base-emitter junction of the fifth transistor 5, the increase in the emitter current of which reduces the limits on the base current of the third transistor 3. When applied to the negative polarity signal input power amplifier works in a similar way. 1 il.

Description

The invention relates to radio engineering and can be used in the output stages of operational amplifiers, as well as in the output stages of integrated amplifiers of low frequency household radio equipment.,

The drawing shows a circuit diagram of a power amplifier (PA).

The purpose of the invention is to expand the dynamic range.

The PA contains the first-sixth transistors 1-6, the first 7 and second 8 current sources, the first 9 and second 10 resistors, the first 11 and second 12 diodes.

UM works as follows.

The operating mode of the PAs of the current sources 7 and 8, the magnitude of the current being quiescent is based on considerations of obtaining permissible harmonic coefficients and efficiency and can be quite small. The voltage drop between the bases of the first 1 and the fifth 5 transistors is equal to the voltage drop on the first forward diode 11, the voltage drop between the bases of the second 2 and sixth 6 transistors is equal to the voltage drop on the second straight diode 12.

Taking into account that the first 1 and second 2 transistors due to the currents of the first 7 and second 8 current sources are in active mode and the voltage drop across their bae-emitter transitions is approximately equal to the voltage drop on a forward-shifted diode, in the absence of an input signal n The 5th and 6th 6 transistors turn out to be closed. And the UM does not affect the operation.

When a signal is applied to the input of the PA, for example, of a positive polarity, the first transistor 1 begins to close and the fraction of the current of the first current source 7 flowing into the base of the third transistor 3 begins to increase, as a result of which the output voltage repeats the input voltage. As the input voltage rises, the emitter-voltage of the first transistor 1 continues to decrease, and the base current of the third transistor 3 increases. In this case, the base current of the third transistor 3 is limited by the value of the initial current value of the first current source, since the emitter current of the first one decreases

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transistor 1 is associated with a decrease in voltage at its Bae-emitter junction, and, therefore, with an increase in the opening voltage at the base-emitter junction of the fifth transistor 5. As a result, even before the base current of the third transistor 3 begins to limit, the input signal open the fifth transistor 5. An increase in the emitter current removes the limitations on the base current of the third transistor 3 n, as a result, on the output voltage.

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When a negative polarity signal is applied to the input, the PA operates in a similar way.

Claims (1)

Invention Formula The power amplifier containing the first and second transistors having a different structure and connected according to a common-collector circuit, the bases of which are connected and are the input of the power amplifier, the emitters are connected to the first and second power supply lines through the first and second current sources, the third and fourth, respectively. transistors having the structure of the second and first transistors, respectively, connected according to a common collector circuit, the emitters of which are connected and are the output of the power amplifier, and the bases are connected to the emitters The first and second transistors, respectively, are characterized by the fact that, in order to expand the dynamic range, the fifth and sixth transistors are included, connected in a common collector circuit and having the structure of the second and first transistors, respectively, the first and second diodes, the first and second resistors, the emitters of the fifth and sixth transistors are connected to the emitters of the first and second transistors, respectively, the base of the fifth transistor is connected to the first power supply bus through the first resistor, and through the first diode to the input of the power amplifier, the base of the sixth transistor through the second resistor is connected to the second power supply bus, and through the second diode to the input of the power amplifier.