JPS6058602B2 - Amplified output circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an amplification output circuit, and in particular to m゛L (Bri
dged or BalancedTransformer
The target is an amplification output circuit that can be used both as a (less) amplification circuit and a dual (Dlkll) amplification circuit.

A BTL amplification circuit uses two amplification output circuits to obtain output signals of mutually opposite phases between their output terminals based on one input signal. It is intended to drive a load.

Since this circuit has two amplifier circuits,
By separating these, it can be used as a two-channel amplification output circuit. However, when configuring an amplification output circuit that can be used as both an mL amplification circuit and a dual amplification circuit in a monolithic integrated circuit, switching between the two must be performed using external terminals, which causes problems such as an increase in the number of external terminals. have a problem

This invention minimizes the increase in external terminals and
The BTL amplifier circuit was designed to provide a low distortion factor, and the dual amplifier circuit was designed to provide an amplification output circuit with uniform characteristics. This invention is a differential amplifier circuit as an input circuit, in which the common emitters of the differential pair transistors are connected to an external terminal, and one output of this differential amplifier circuit is input, and the amplified output is a first amplification output circuit that supplies a signal to a first external output terminal; and a second amplification output circuit that receives the other output of the differential amplification circuit and supplies the amplified output signal to a second external output terminal. The present invention attempts to obtain an amplification output circuit configured in a monolithic integrated circuit.

Hereinafter, the present invention will be specifically explained with reference to Examples.

FIG. 1 is a circuit diagram showing an embodiment of the present invention.
This circuit is composed of a differential amplifier circuit 2 as an input circuit, and positive phase amplifier circuits 3 and 4 each receiving the differential output as an input.

The differential amplifier circuit 2 connects the bases of its input differential pair transistors Ql, Q2 to external terminals Pl, P2 of the monolithic integrated circuit 1 constituting each circuit. The common emitter terminals of the differential pair transistors Ql and Q2 are connected to the external terminal P3 in the same manner as described above.
Further, it is assumed that the output terminals of the positive phase amplifier circuits 2 and 3 are connected to external terminals P4 and P5, respectively. In addition, other terminals as a monolithic integrated circuit, such as a power supply voltage terminal,
Ground terminals and the like are omitted.

When the amplification output circuit 1 as described above is used as a BI'L amplification circuit, the external circuit is configured as follows.

An input signal is applied to one input terminal, for example, external terminal P1, and a predetermined bias voltage (alternating current grounding) is applied to the other input terminal P2, and external terminal P5 is left open. By doing so, this input circuit is operated as a differential amplifier circuit.

In this case, a load is connected between the external terminals P4 and P5, which are the output terminals of the positive phase amplifier circuits 3 and 4. As a result, the positive-phase amplifier circuits 3 and 4 amplify and output signals formed by the differential amplifier circuit 2 that are in opposite phases to each other with respect to the input signal. By outputting and driving, a BTL amplifier circuit can be constructed. On the other hand, when the amplification output circuit 1 as described above is used as a dual amplification circuit, the external circuit is configured as follows. In addition, a dual amplifier circuit is a circuit in which a signal obtained by amplifying the first input terminal signal of the first input terminal P1 is transmitted to the first output terminal P5, and a second input signal of the second input terminal P2 is amplified. A signal is transmitted to the second output terminal P4, and the signal is transmitted from the first input terminal P1 to the first output terminal . A two-signal amplification circuit is defined in which signal transmission up to P5 and signal transmission from the second input terminal P2 to the second output terminal P are performed independently of each other.

Therefore, such a dual amplification circuit can be used to independently amplify a stereo left channel signal.

External terminals Pl, P2 are used as input terminals of the respective amplifier circuits, input signals are applied thereto, and external terminals P, P2 are connected to the common emitter of the differential transistors Ql, Q2.
By grounding the input circuit in an alternating current manner, this input circuit operates as an emitter-grounded amplifier circuit.

In addition, an external terminal P which is the output terminal of the positive phase amplifier circuits 3 and 4
4. A load is connected between P5 and the AC ground terminal, respectively. As a result, the input circuit 1 operates as a common emitter amplifier circuit, so that the transistors Ql,
The collector output of Q2 amplifies each input signal independently of each other to form an output signal.

Therefore, the output signals obtained from these through the positive phase amplifier circuits 3 and 4 correspond to the respective input signals, and a dual amplifier circuit can be constructed. When a BTL amplifier circuit and a dual amplifier circuit are used, two input terminals and two output terminals are required.

In addition, in this embodiment, in order to switch between the two, the common emitter terminal of the differential amplifier circuit 2 is provided as an external terminal as described above, and the number of external terminals is increased by one. can be kept to a minimum. Furthermore, the circuit of the embodiment has the following features when used as a BTL amplifier circuit.

In general, the input/output transfer characteristics of an amplifier circuit have nonlinear characteristics, as shown in FIG.

In the case of a positive phase amplifier circuit, as shown by the solid line, distortion occurs in the output signal such that the positive half cycle of the input signal is expanded and the negative half cycle of the input signal is compressed. In this embodiment circuit, since the input signals of the positive phase amplifier circuits 3 and 4 are signals with opposite phases to each other, their outputs also become signals with opposite phases as shown by solid lines and broken lines in the figure, and the difference potential between them is is applied to the load.

Therefore, in the positive half cycle of the input signal of the differential amplifier circuit 2, the output signal expanded by the amplifier circuit 3 (solid line) and the output signal compressed by the amplifier circuit 4 are distorted by each other. It acts to cancel out. Further, even in the negative half cycle of the input signal, the output signal compressed by the amplifier circuit 3 and the output signal expanded by the amplifier circuit 2 act to cancel each other's distortion components. In other words, the even-order harmonic components generated in the outputs of the amplifier circuits 3 and 4 appear as in-phase signals.

Therefore, in the BTL amplification circuit that outputs the output voltage difference between the amplification circuits 3 and 4, the distortion caused by the even-order harmonics can be canceled out as an output signal, and generally, two of the nonlinear distortions are The third harmonic component is the largest, and by canceling it, the output amplitude of the BTL circuit is doubled, and the distortion factor is significantly reduced. In addition, in this embodiment circuit, since the output is the difference voltage between the positive phase amplifier circuits 3 and 4, the influence of disturbances such as power supply fluctuations (including power supply ripples) on the output signal waveform is reduced. Since the signals are generated as in-phase signals, they are canceled out as output signals, and output distortion caused by these signals can be reduced. especially,
It can also cancel out the hop sound when the power is turned on. Furthermore, as shown in FIG. 3, in order to form input signals with opposite phases to each other, a BTL amplifier circuit may be used, in which an inversion circuit 5 is provided on one input side, or the inversion circuit 5 may be omitted and the other input signal may be inverted. In a BTL circuit in which the amplifier circuit 4 is a reverse phase amplifier circuit and the output of one amplifier circuit 3 is directly inverted to form outputs having opposite phases, the signal transmission path for the input signal is However, as shown in this example circuit, by making the amplification paths symmetrical with respect to the input signal, the above-mentioned phase difference can be avoided. Problems caused by misalignment can also be resolved.

This also applies when used as a dual amplifier circuit.
This is very convenient because the characteristics of both amplifier circuits are matched.

In particular, in the case of a monolithic integrated circuit, variations in the characteristics of each element are canceled out, and the circuit of this embodiment can be said to be suitable for monolithic integrated circuit formation.

Note that in this embodiment circuit, the distortion in the input circuit 2 is not corrected from the viewpoint of distortion rate;
Whether it is a TL amplifier circuit or a dual amplifier circuit, there is no need to use a large amplification factor, and in the case of a differential circuit, the input/output transfer characteristics have excellent linearity, so distortion in this circuit is not a problem. do not become.

The present invention is not limited to the above-mentioned embodiments, and the differential amplifier circuit 2 may include a differential pair of transistors made of Pnp transistors, and the amplifier circuits 3 and 4 may both be configured as anti-phase amplifier circuits. good.

However, since the output impedance of the differential amplifier circuit is large, from the viewpoint of impedance matching, it is preferable to use a positive-phase amplifier circuit with a high input impedance. The specific circuits of these amplifier circuits may be any power amplifier circuit used for power 1C whose output circuit is a single-ended push-pull circuit or the like.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 is an input/output transfer characteristic diagram of a booster circuit, and FIG. 3 is a circuit diagram showing an example of a BTL circuit. 1... Monolithic integrated circuit (amplification output circuit), 2...
...Differential amplifier circuit (input circuit), 3, 4... Positive phase amplifier circuit, 5... Inverter circuit.

Claims (1)

[Claims] 1. A differential amplifier circuit in which the bases and common emitters of the differential pair transistors are respectively connected to external terminals, and a monolithic integrated circuit that is the same as this differential amplifier circuit, and one output of the differential amplifier circuit. a first amplification output circuit which takes as an input and supplies the amplified output signal to a first external output terminal; an amplification output circuit comprising a second amplification circuit for supplying to an output terminal, the amplification output circuit is operated in a BTL manner by opening the common emitter, and by grounding the common emitter in an alternating current manner; An amplification output circuit characterized in that the amplification output circuit is capable of performing dual amplification operation.