JPS61131906A - Power amplifier - Google Patents

Abstract

PURPOSE:To realize a low distortion factor and to decrease a DC voltage difference between outputs by placing a non-inverting negative feedback amplifier circuit to the 1st stage and inverting the phase by an inverting negative feedback amplifier circuit so as to decrease the variance in the voltage gain. CONSTITUTION:When a signal is inputted to an input terminal 115, a non-inverting negative feedback amplifier circuit 101 having a gain 0dB inputs a signal having the same amplitude and in phase with the input signal to a negative feedback circuit 103, from which a signal amplified by a factor of the gain is outputted to an output terminal 117. On the other hand, a signal inputted to an inverting negative feedback amplifier circuit 102 with gain 0dB via the circuit 101 becomes an inverted signal with the same amplitude as the input signal, amplified by a negative feedback circuit 104 and outputted to an output terminal 118. In this case, the gain of the circuits 101, 102 is the unity, the feedback rate is the unity and the voltage gain variation and distortion factor of each amplifier circuit are decreased to 1/(1+Avo) with respect to those at no feedback and then the circuit is stabilized, where Avo is the voltage gain. Further, the voltage gain variance is compressed to stabilize the DC voltage difference between output terminals thereby realizing a low distortion factor.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a BTL (usually referred to as BTL and this abbreviation will be used hereinafter) type amplifier circuit.

[Conventional technology]

The so-called BTL type amplifier circuit uses two sets of amplifiers, drives the outputs of each amplifier so that the phases of the signals are opposite to each other, and connects a load between the output terminals to create a single amplifier. This is an amplifier configured so that it can supply twice the output voltage to the load, and if the impedance of the load is the same, it can extract four times the power signal of a single amplifier.

An example of a conventional BTL type amplifier circuit has a circuit configuration as shown in Fig. 2. This circuit has a common emitter connected to a constant current source 11 (PNP)? Load resistors 3 and 4 are connected to the collectors of transistors 1 and 2, respectively, and a human input signal is applied to the base of PNP) run raster 20 via the input terminal 16. A differential amplifier 50 with a differential configuration as a second output, and an L differential amplifier 50
A tenth negative feedback amplifier circuit 13 whose tenth output is human powered and has feedback resistors 5, 7 and a capacitor 6, and a second negative feedback circuit whose second output is human powered and has feedback resistors 8, 10 and a capacitor 9. It is composed of an amplifier circuit 14.

In this circuit, when a signal is input to the input terminal 16, the first . Signals with opposite phases are output to the second outputs, respectively, and the first... The second output signals are respectively the first . Amplified by the second negative feedback amplification circuit 813.14,
Signals with opposite phases are also output to the output terminal 18 and the output terminal 19, respectively.

Therefore, the load resistor 15 connected between the output terminals 18 and 19
It is possible to obtain four times the output power of a single amplifier.

Note that the capacitors 6.9 and 1. This is to prevent the second negative feedback amplifier circuit wr13.14 from having a DC voltage gain, the constant current source 11 is for operating the differential amplifier 50, and the constant voltage source 12 is for PNP
) is for biasing the pace of transistor 1.

[Means for the invention to solve the problem]

When using this BTL type amplifier circuit, the first stage differential m
In the differential amplifier 50, since there has never been feedback, there is no compression effect due to the feedback, and the voltage gain of the differential amplifier 50 has large variations in voltage gain. The DC voltage difference between the second outputs is large, and a low distortion rate cannot be expected even if the distortion rate is low. Then, a pjk system using this differential amplifier 50.

Even as a BTL type amplifier circuit, the voltage gain is large, the voltage difference between the output terminals 18 and 19 is large, and there is a limit to the distortion rate.

It is an object of the present invention to reduce variations in voltage gain, reduce direct R and voltage differences between output terminals, and further,
An object of the present invention is to provide a BTL type amplifier circuit that can realize a low distortion rate.

[Means for solving problems]

According to the present invention, a negative feedback human power amplifier receiving an input signal;
a tenth negative feedback power amplifier that amplifies the output of the negative feedback human power amplifier; and a gain 111 that receives the output of the negative feedback input amplifier.
A zero inversion base negative feedback amplifier, a second negative feedback power amplifier that amplifies the output of the inversion negative feedback amplifier circuit, and a load connected between the output terminals of the first and f742 negative feedback power amplifiers. Get a power amplifier containing.

〔Example〕

Hereinafter, specific embodiments of the present invention will be described using FIG. 1.

A non-inverting negative feedback amplifier circuit 101 with a gain of OdB is connected to the input terminal 115, and a feedback resistor 107 is connected to the output of the non-inverting negative feedback amplifier circuit 101.
and 109 and a capacitor 108 and an inverted negative feedback amplifier circuit 102 with a gain of OdB, feedback resistors 110 and 112 and a capacitor 11
1 is connected to the negative feedback amplifier circuit 104. A load resistor 114 is connected to both output terminals 117 and 118 of the negative feedback amplifier circuits 103 and 104. Negative feedback amplifier circuit 10
3. 104 is configured as a non-inverting type, and the negative feedback amplifier circuit 102 is configured as an inverting type. The negative feedback amplifier circuit 101 is
Since the gain is Ode, a signal having the same amplitude and the same phase as the input signal is input to the negative feedback amplifier circuit 103, and the negative feedback amplifier circuit 1
The signal multiplied by the gain at 03 is output to the output terminal 117. On the other hand, since the gain of the inverting negative feedback amplifier circuit 102 is OdB, the signal input manually to the inverting negative feedback amplifier circuit 102 via the non-inverting negative feedback amplifier circuit 101 becomes an O signal with the same amplitude and opposite phase as the human input signal. Increased by the negative feedback amplifier circuit 104
and output to the output terminal 11B.

In addition, signals having mutually opposite phases are output to the output terminals 117 and 118, and if a load 114' is connected, four times the power can be obtained compared to a single amplifier. As a BTL type amplifier circuit, this is similar to the nine-conductor circuit shown in FIG. Furthermore, an inverting negative feedback amplifier circuit 1'02 is used for phase inversion, and the difference from the conventional circuit shown in FIG. 2 is that the first stage differential amplifier 50 is non-feedback.

Generally, in the case of a negative feedback amplifier circuit, if the voltage gain without feedback is Avo and the feedback rate is β, then the fluctuation of the voltage gain of the negative feedback amplifier circuit is the voltage gain Av without feedback.

It is well known that the fluctuation of the signal is compressed to 1/(1+Avoβ), and the distortion rate is felt to be 17(1+Avoβ), which is the distortion rate when there is no feedback.

Therefore, in this embodiment, the non-inverting negative feedback amplifier circuit 10
Since the gain of the 1-inverting negative feedback amplifier circuit 102 is 11', the feedback factor β = 1. The voltage gain fluctuation and distortion rate of each amplifier circuit are felt and stabilized as l/1 + Avo when there is no feedback. .

In addition, since fluctuations in voltage gain are compressed to 1/1+Avo, the DC voltage difference between the output terminals is also stabilized.
Even as a BTL type amplifier circuit, fluctuations in the voltage gain are small, and the DC voltage difference between the output brackets 117 and 118 is also small, making it possible to achieve a low distortion rate.

〔Effect of the invention〕

As described above, according to the present invention, in a BTL type amplifier circuit, a non-inverting negative feedback amplifier circuit is provided at the first stage, and phase inversion is performed by an inverting negative feedback amplifier circuit.
It is possible to reduce variations in voltage gain, reduce output amount DC voltage difference, and achieve low distortion.

[Brief explanation of drawings]

FIG. 1 is a wiring diagram showing a BTL type amplifier circuit according to an embodiment of the present invention, and FIG. 2 is a wiring diagram of a conventional BTL type amplifier circuit. 1.2...PNP) Tunjista, 3, 4, 5,
7゜8.10,105,106,107,109,11
0°112...Resistance, 6,9,108,111
... Capacitor, 11 ... Constant current source,
12,113... Constant voltage source, 13,14,10
1,102,103,104...-negative feedback amplifier circuit, 15,114...load, 16,115...
...Input terminal, 17,116...Power supply layer,
18゜19.117,118... Output trend, 2
0,119... Grounding trend. 1,・-),.

Claims (1)

[Claims] A tenth negative feedback amplifier circuit that receives an input signal applied to an input terminal, and a second negative feedback amplifier circuit that amplifies the output of the first negative feedback amplifier circuit.
an inverting negative feedback amplifier circuit with a gain of "1" that receives the output of the first negative feedback amplifier circuit; and the inverting negative feedback amplifier circuit. A power amplifier comprising: a third negative feedback amplifier circuit that amplifies an output; and a load connected between the outputs of the first and second negative feedback amplifier circuits.