JPS6024714A - Voice mixing circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an audio mixing circuit that synthesizes and outputs two audio input signals.

Conventional configuration and problems thereof First, an example of a conventionally used audio mixing circuit will be described with reference to FIG. 1, 3, 6 in the figure.
12 are capacitors for canting DC components, one end of which is connected to an audio input signal, and the other end is connected to a resistor 2. It is connected to the base of transistor 100 via capacitor 6.

Further, another audio input signal B is applied to one end of the capacitor 3, and is applied to the drain of the FET 4 via this. The source of FET 4 is connected to the connection point between capacitor 6 and resistor 2 through resistor 5 . A control signal is applied to the gate of FET4.

A resistor 7 is connected between the power supply and the base of the transistor 100, and a resistor 8 is a bias resistor connected between the base of the transistor 1o and ground.

A resistor 11 is an emitter resistor of the transistor 10, and a resistor 9 is a load resistor connected between the collector of the transistor 10 and the power supply. Further, the capacitor 12 is connected to the collector of the transistor 10, and the synthesized audio output signal is outputted from the other end.

Next, the operation of this circuit will be explained. The audio input signal B is turned on and off by the FET 4 in accordance with the control signal to control whether or not to perform audio synthesis. After that, the audio input signal 4A
, B are combined, and the loss caused by the resistor 2.6 is amplified by the transistor 10 and output.

However, in these conventional circuits, it is necessary to use an expensive switching element using FET 4, and since the DC component of all signals is canted with a capacitor of 1°3.6.12, the DC The disadvantage is that it cannot be transmitted at all.

Purpose of the Invention The present invention eliminates the above-mentioned drawbacks of the conventional technology, allows a circuit to be constructed without using expensive switching elements such as FETs, and is also capable of transmitting the DC component of one audio signal. The purpose is to provide an audio mixing circuit.

Structure of the Invention In the present invention, by limiting the base current of a control transistor and using the active region of the transistor to perform a switching operation, control performance equivalent to or higher than that of an FET is achieved, and a DC component is further transmitted. Therefore, the mixing is performed by an emitter follower circuit.

DESCRIPTION OF THE EMBODIMENTS An audio mixing circuit according to an embodiment of the present invention will be described below with reference to FIG. In FIG. 2, one audio input signal is applied through resistor 13 to the base of transistor 14. In FIG. The other audio input signal B is connected to the capacitor 19.
It is inputted to the collector of transistor 1B via , and from its emitter is further applied to the base of transistor 160 via capacitor 17 . Transistors 14 and 16 have their collectors and emitters connected together, with their common collectors connected to a power supply and their common emitters connected through a resistor 15 to ground. A control signal is applied to the base of transistor 18 via resistor 2o, and an audio output signal is output from the common emitter of transistors 14 and 16.The operation of this circuit will now be described. Audio input signal A I
d is output as an emitter follower output through the transistor 14.

The other audio input signal B is transmitted from the collector to the emitter of the transistor 18 because the transistor 18 is conductive when a control signal is applied to the base of the transistor 18 via the high resistance 2o, and is further transmitted to the capacitor. 17 to the base of transistor 16. Therefore, at this time, two audio input signals A are generated at the common emitter of transistor 14 and transistor 16.

B is combined and output.

When no control signal is applied to the base of transistor 18, transistor 1B is in a cut-off state and audio input signal B is not transmitted to transistor 16, so that only audio input signal B is output at this time.

In this way, transistor 18 is connected to capacitor 17.19.
Since the direct current is cut off and used, it is possible to operate in an active region where the current amplification factor is close to 1, and it is possible to perform good control of characteristics with little distortion. Therefore, this allows F
Expensive switching elements such as ETs are not required, and an inexpensive circuit can be obtained.

Also, the DC component of the audio input signal can be transmitted to the output terminal via the emitter follower circuit.

Effects of the Invention As described above, according to the present invention, by using the control transistor in the active region where the DC amplification degree is approximately 1, F
It is possible to obtain a circuit that exhibits good control effects with characteristics equal to or better than ET at a low cost, and furthermore, by effectively using the emitter follower circuit, it is possible to transmit the DC component of the audio input signal to the output signal. .

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a conventional audio mixing device. FIG. 2 is a circuit diagram of an audio mixing device according to an embodiment of the present invention. 13.15... Resistance, 14.16...
Transistor for synthesis, 17.19... Capacitor for DC cut, 18... Transistor for control, 2o... Resistor.

Claims (1)

[Claims] One of the two audio input signals is the first audio input signal.
in addition to the collector of the transistor, and from its emitter through the capacitor to the base of the second transistor,
A control signal is applied to the base of the first transistor, another internal audio force signal is applied to the base of the third transistor, the collectors and emitters of the second transistor and the third transistor are connected in common, respectively; An audio mixing circuit that connects a common emitter to ground through a resistor, connects the common collector to a power supply, and outputs a synthesized audio output signal from the common emitter.