SU1420643A1 - Power amplifier - Google Patents

Abstract

The invention relates to radio engineering. The purpose of the invention is to expand the dynamic range. The device contains in each arm an input cascade on a transistor (T) 1, an output cascade on T2 and 3, a switching diode 4, a threshold el-th on Zener diode 5, a non-linear el-6, high-voltage and low-voltage sources 7 and 8 of the power supply, and a load 9 With an increase in the input signal, the collector current T 1 increases, which through a non-linear el-6 enters the base T 3 and is amplified by it. The TOR is in the linear mode of operation until the voltage at load 9 approaches the voltage of source 8. T 3 is saturated, and its coefficient is. current gain drops sharply. An increase in the collector current T 1 at saturation T 3 leads to a sharp increase in voltage on the nonlinear element 6, which leads to the breakdown of Zener diode 5 and an increase in current through the base T 2, which increases the voltage on the emitter T 3. The diode 4 closes by disconnecting the source 8 from T 3. T 3 goes out from the state close to saturation, its base current decreases, the voltage on the non-linear element 6 drops and the Zener diode 5 closes, i.e. The T 3 operation mode, which is close to saturation, is automatically maintained. The goal is achieved by introducing a non-linear element 6, the internal resistance of which varies in phase with the base current T 3 1 sludge. (L

Description

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About O5 1 SB

This invention relates to radio engineering and can be used in low frequency amplifiers with increased output power.

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

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

The push-pull power amplifier in each arm includes an input stage on the first transistor 1, an output stage on the second and third transistors 2 and 3, a switching diode 4, a threshold element made at Zener diode 5, a nonlinear element 6, the internal resistance of which is in phase with voltage input, high-voltage and low-voltage power sources 7 and 8, load 9.

The input signal is fed to the bases of the first transistors 1, and the upper arm of the circuit serves to amplify the positive half-wave signal, and the lower one - negative. Since both arms of the circuit work in a similar way, consider the work of the upper arm.

As the input signal increases, the collector current of transistor 1 increases, which through nonlinear element 6 enters the base of transistor 3 and is amplified by it. The voltage across the zener diode b in this case is equal to

UcT U7 - U8-f Ufl,:, + U ,,, 6,

where and us is the voltage source of sources 7 and 8

nutrition; Usj.-j - voltage base - emitter

transistor 3;

Uirjg is the voltage across the nonlinear element 6, close to zero in this mode, i.e. when the current through the nonlinear element 6 is less than its maximum current.

The stabilization voltage of the Zener diode 5 is slightly higher than the voltage of the UCT with a small input voltage, where UCT is the voltage drop across the Zener diode 5, and the Zener diode 5 is closed in this mode. The current through the base of the transistor 2 does not leak. Transistor 3 is in linear mode of operation until the voltage at load 9 approaches the voltage of source 8. Transistor 3 is saturated and its current gain drops sharply. Nonlinear element 6

calculated for the maximum base current of the transistor 3 in the linear mode of its operation. Increasing the collector current of transistor 1 while saturating transistor 3 results in

a sharp increase in voltage on the nonlinear element 6, which leads to the breakdown of Zener diode 5 and an increase in current through the base of transistor 2, which increases the voltage at the emitter of transistor 3. Switching diode 4 closes, disconnecting the power supply 8 from transistor 3. Power supply in this area characteristics are carried out from series-connected sources 7 and 8. Transistor 3 goes out of saturation state NIN, and its base current decreases, voltage on nonlinear element 6 drops a little, Zener diode 5 closes . Practically in this case, the operation mode of the transistor 3 is automatically maintained, which is close to saturation, when the voltage

The emitter-collector of this transistor is close to 1.5-2V. Transistor 2 in this case operates in linear mode. With a further increase in the input signal, it opens more and together with the scheme

control supports the specified mode of operation of the transistor 3.

Claims (1)

Invention Formula A power amplifier containing in each arm an input stage, made on the first transistor connected in a circuit with a common emitter and having a single structure, an output stage performed on the second and third transistors connected in series over a constant current having a different structure, in which the collector of the third transistor is a push-pull amplifier output, emitters the third and second transistors are connected via a switching diode to a low-voltage power supply bus and with high voltage bus power supply, respectively, the collector of the first transistor through the threshold element is connected to the base of the second transistor, and the same-name transistors of the shoulders of the push-pull power amplifier have different structures, characterized in that, in order to broaden the dynamic range, a non-linear element is introduced between the collector of the first transistor and the base of the third transistor, the internal resistance of which changes in phase with change the base current of the third transistor.