JPH03252211A - Automatic gain controlled amplifying circuit - Google Patents

Abstract

PURPOSE:To automatically control and adjust the degree of amplification in accordance with the noise level by detecting the noise level to extract a gain control signal corresponding to the noise level at the time of sending a prescribed signal in the noise. CONSTITUTION:A prescribed signal is inputted from a terminal 101 and has the level adjusted by a variable resistor 14 and is amplified to a prescribed level by a gain variable amplifying circuit 11 and is outputted through a terminal 102. In this case, the gain of the circuit 11 is controlled by the control signal sent from a smoothing circuit 13 through a variable resistor 15. Not only the output signal of the circuit 11 but also the mixed signal of a noise signal and the prescribed signal from a terminal 103 is inputted to an echo canceller 12, and only the noise signal is separated from both inputs. This signal is inputted to the circuit 13 and is smoothed and is outputted as a control signal corresponding to the noise signal level. Thus, the degree of amplification of the signal input is automatically controlled and adjusted in accordance with the variance of the noise signal level superposed on the signal.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an automatic gain control amplifier circuit, and more particularly to an automatic gain control amplifier circuit that adjusts the gain for a signal in response to a varying noise level. , the output level of the audio output in a television receiver, radio receiver, etc. is adjusted by a predetermined variable gain amplifier circuit5.Therefore, the audio output level is once set via the variable gain amplifier circuit. Generally, you cannot change the volume unless you reset it.

Problems to be Solved by the Invention In the conventional variable gain amplifier circuit described above, the gain is fixed when the -degree audio output level is set.
There is a drawback that when the ambient noise signal level changes, the gain must be corrected and the volume adjusted in response to the variation in the ambient noise signal level.

The present invention has been made in view of the above-mentioned conventional situation,
SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a novel automatic gain control amplifier circuit which makes it possible to eliminate the above-mentioned drawbacks inherent in the prior art.

Means for Solving the Problems In order to achieve the above object, an automatic gain control amplifier circuit according to the present invention detects the level of the ambient noise signal from a mixed signal of the ambient noise signal and a predetermined signal, and adjusts the level of the noise signal. The device is configured to include means for extracting a gain control signal corresponding to the level, and variable gain amplification means used for amplifying a predetermined signal whose amplification degree is controlled and adjusted by the gain control signal.

Embodiment Next, a preferred embodiment of the present invention will be specifically explained with reference to the drawings.

FIG. 1 is a block diagram showing the main parts of an embodiment of the present invention.4 As shown in FIG. 1, an embodiment of the present invention includes a variable gain amplifier circuit 11, an echo canceller 12, 13 and variable resistors 14 and 15.

In FIG. 1, a predetermined input signal is input from a terminal 1111, its level is adjusted by a variable resistor 14, and amplified to a predetermined level by a variable gain amplifier 11.
]2. In this case, the gain of the variable gain amplifier circuit 11 is controlled by the smoothing circuit 13 through the variable resistor 15.
It is controlled by control signals sent from The output signal of the variable gain amplifier circuit 11 is outputted via the terminal 102 as described above, and is also inputted to the echo canceller 12. A mixed signal of a noise signal and a predetermined signal is input to the echo canceller 12 from the terminal 11]3 to the output signal of the variable gain amplifier circuit 11, and only the noise signal is separated from both inputs and output. The output of this noise signal is input to the smoothing circuit 13, smoothed, and outputted from the smoothing circuit 13 as a control signal corresponding to the noise signal level.
The signal is input to the variable gain amplifier circuit 11 via the variable resistor 15. As already mentioned above, the gain of the variable gain amplifier circuit 11 is controlled and adjusted by the control signal.6 Therefore, in this embodiment, the control signal is used to control and adjust the gain of the variable gain amplifier circuit 11. , the amplification degree for the signal input is automatically controlled and adjusted.

As described in detail, according to the present invention, when a predetermined signal is sent out in noise, the noise level is detected and the gain control signal corresponding to the noise level is extracted, thereby adjusting the sound reduction level. It is possible to easily provide an automatic gain adjustment amplifier circuit that can automatically control and adjust the amplification degree in accordance with the above.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the main parts of an embodiment of the present invention.

Claims (1)

[Claims] means for detecting the noise signal level from a mixed signal of a noise signal and a predetermined signal and extracting a gain control signal corresponding to the noise signal level; An automatic gain adjustment amplifier circuit comprising: variable gain amplification means used for amplification.