JPS5811057Y2 - mixing circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a mixing circuit that mixes a first signal and a second signal from different sound sources, such as radio sound and microphone sound.

The circuit shown in Fig. 1 is a conventionally commonly used mixing circuit, and in the figure, 1 and 2 are input terminals to which first and second signals from different sound sources are applied, and 3 and 4 are input terminals of the signals. Variable resistor to adjust the level, 5 is an amplifier circuit,
6 is a speaker that emits the signal amplified by the amplifier circuit 5;

In such a conventional mixing circuit, resistors 7 and 8 are inserted and connected in the signal path as shown in the figure in order to prevent the signal from being influenced by other input signals.

Although it is possible to make the mutual interference negligible by increasing the values of the resistors 7 and 8, it has the disadvantage that the gain of the entire circuit decreases because the resistors are connected in the signal path. There is.

This is a big problem now that even in portable devices, the output of amplifier circuits is increasing.

Balanced transformerless (hereinafter referred to as BTL) is a method of increasing the output of an amplifier circuit.

) connection, and the present invention relates to a mixing circuit in such a BTL connected amplifier circuit.

Generally, in a low-frequency amplifier circuit of an output-less (OTL) type, the output stage is a push-pull connection, and when configured with an integrated circuit, a differential amplifier is installed in the preamplification stage to improve temperature characteristics. In many cases, the control electrodes of the differential pair active elements of the differential amplifier are used as input terminals.

The present invention is intended to provide a mixing circuit in an amplifier circuit in which circuit blocks such as integrated circuits configured in this manner are connected in a BTL manner, and will be explained below with reference to the drawings.

FIG. 2 shows an embodiment of the mixing circuit of the present invention, and in the same figure, 9 and 10 are first and second circuit blocks having the same circuit configuration, each having a differential amplifier at the input section as described above; Reference numerals 11, 12, 13 and 14 are input terminals connected to respective control electrodes of active elements constituting the differential amplifier.

Input terminals 15 and 16 are respectively applied with first and second signals from different sound sources, and variable resistors 17 and 18 adjust the input level of the signals.

A speaker 19 is connected as a load between the output terminal of the first circuit block 9 and the output terminal of the second circuit block 10, and the signal obtained from the output terminal of the first circuit block 9 is transmitted by a resistor 20.21. The signal is divided and applied to the input terminal 14 of the second circuit block 10.

The first human power signal applied to the input terminal 15 has its level adjusted by the variable resistor 17, and then the second human power signal applied to the input terminal 11 of the first circuit block 9 and the input terminal 16 is After the level is adjusted by the variable resistor 18, the second
It is connected to be applied to the input terminal 13 of the circuit block 10.

The present invention is constructed as described above, and its operation will be explained next.

First, the first input signal applied to the input terminal 15 is BTL.
Connected first circuit block 9 and second circuit block 1
0 and emitted from the speaker 19.

The second input signal applied to the input terminal 16 is amplified by the second circuit block 10 and emitted from the speaker 19.

As is clear from this operation explanation, the first circuit block 9 and the second circuit block 10 are BTL only for the first human input signal.
In order to control the operation, when the level of the first human power signal and the second human power signal are the same, the first human power signal is amplified to a greater extent, but by adjusting the variable resistor 17, its output level can be adjusted. If they are made the same, there will be no problem with the mixing operation.

Note that the BTL-connected amplifier circuit is well known, and a description of its operation will be omitted.

As explained above, the mixing circuit of the present invention is BTL
Since the second signal is applied to the input terminal of one circuit block in an amplifier circuit that can be connected to obtain a large output, a resistor is placed in the signal path to prevent mutual interference between the signal systems as in the conventional case. There is no need to insert it at all, and therefore there is no problem in increasing the output of the amplifier circuit, and the practicality of the present invention is extremely high.

[Brief explanation of drawings]

FIG. 1 shows an embodiment of a conventional mixing circuit, and FIG. 2 shows an embodiment of the mixing circuit of the present invention.

Claims (1)

[Scope of utility model registration request] The first and second circuits of the same circuit configuration, such as an integrated circuit, are equipped with a differential amplifier having a first and second active element in the input section, and have first and second input terminals that are in an antiphase relationship with each other. and a load is connected between the output terminals of the first circuit block and the output terminal of the second circuit block, and a first input signal is applied to the first input terminal of the first circuit block, and a signal from the output terminal of the first circuit block is applied to the second input terminal. In the amplifier circuit configured to supply large power to the load by applying it to a second input terminal of a circuit block, a sound source different from the first input signal is applied to the first input terminal of the second circuit block. 1. A mixing circuit characterized in that the second input signal is not applied to the load so that the first input signal and the second input signal are mixed and supplied to the load.