JPH06103816B2 - Semiconductor integrated circuit device - Google Patents

Description

The present invention relates to a semiconductor integrated circuit device suitable for application to a voice circuit such as a VTR.

[Outline of Invention]

The present invention relates to a semiconductor integrated circuit device suitable for application to a voice circuit such as a VTR, for example, an amplifier circuit to which an input signal is supplied from an input terminal, an output level of the amplifier circuit and a first amplifier circuit.
Of the control signal based on the comparison result, and the level of the control signal from the detection circuit and the second reference level are compared with each other to obtain the comparison result. Used in common with both monaural and stereo audio circuits by providing a control current signal based on this control circuit to control the gain of this amplifier circuit In addition, it is possible to obtain excellent stereo sound when used in a stereo type sound circuit.

[Conventional technology]

Conventionally, for example, in a VTR audio signal recording apparatus, a semiconductor integrated circuit device (1) as shown in FIG. 5 is used.

In FIG. 5, (6) indicates an input terminal to which an audio signal is input, and the audio signal from this input terminal (6) is output to the output terminal (7) and the detection circuit (2) through the voltage control amplifier circuit (8). ) Respectively.

The detection circuit (2) compares the level of the audio signal with the level of the reference voltage V _ref , and supplies a control voltage based on the result to the voltage control amplifier circuit (8). Thereby, the gain of the voltage control amplifier circuit (8) is the maximum gain when the level of the audio signal supplied to the detection circuit (2) is equal to or lower than the level of the reference voltage V _ref (= V _rer ′). Audio signal level is reference voltage V
When the value exceeds _ref, as shown in FIG. 7A, the gain is such that the output signal becomes substantially constant with respect to the input signal.

Although one semiconductor integrated circuit device (1) described above is used in a monaural signal recording device, when the semiconductor integrated circuit device (1) that constitutes this AGC circuit is used in a stereo type audio signal recording device, two semiconductor integrated circuit devices are used. Will be needed. However, in that case, since the gain control of both semiconductor integrated circuit devices is performed separately, for example, the level of one audio signal is set to the reference voltage V _ref.
When the level of the other audio signal is equal to or lower than the reference voltage V _ref , the gain of one voltage control amplifier circuit (8) is controlled to be small, and the gain of the other voltage control amplifier circuit (8) is the maximum gain. As a result, the level difference between the one audio signal and the other audio signal becomes small, and there is the inconvenience that a stereo feeling cannot be obtained. In order to eliminate such an inconvenience, as shown in FIG. 6, a method of averaging the control voltages of two semiconductor integrated circuit devices with a capacitor C has been proposed.

In FIG. 6, the L channel audio signal input terminal (6
The L channel audio signal supplied to L) is supplied to the output terminal (7L) through the voltage control amplifier circuit (8L) and also to the detection circuit (2L).

On the other hand, the R-channel audio signal supplied to the R-channel audio signal input terminal (6R) is supplied to the output terminal (7R) through the voltage control amplifier circuit (8R) and the detection circuits (2L) and (2L).
R) are connected to each other, and the control voltage of each of them is averaged by one capacitor C connected to the midpoint of the connection.

In this case, even if one of the input audio signals has a fairly high level and the other audio signal has a low level, when the average value of the control voltage becomes equal to or higher than the reference voltage V _ref , the voltage control of the one and the other is performed. Since the gains of the amplifier circuits (8L) and (8R) are both lowered, the output audio signal is controlled so that the level is lowered, and the other audio signal is also controlled so that the level is lowered. The level difference between the one and the other audio signals is maintained, and good stereo audio can be obtained.

[Problems to be Solved by the Invention]

By the way, in the above case, the semiconductor integrated circuit device (1L) and (1R) due to variations in so-called semiconductor integrated circuit device
The respective reference voltages V _ref of may not be equal to each other. In this case, the gains corresponding to the control voltages supplied from the respective detection circuits (2L) and (2R) to the voltage controlled amplifier circuits (8L) and (8R) are also different.

For example, assume that the reference voltage V _ref and V _ref ′ of the detection circuit (2L) and the voltage control amplifier circuit (8L) of the semiconductor integrated circuit device (1L) are V ₁ and V ₁ ′, respectively. Further, these voltage values V ₁ and V ₁ ′ are equal because they are formed in the same semiconductor integrated circuit device (1L).

Further, the respective voltage values of the reference voltages V _ref and V _ref ′ of the detection circuit (2R) and the voltage control amplifier circuit (8R) of the semiconductor integrated circuit device (1R) are V ₂ and V ₂ ′, respectively. Also, these respective voltage values V ₂ and V ₂ ′
Can be made equal because they are formed in the same semiconductor integrated circuit device (1R).

At this time, it is assumed that the voltage value V ₁ of the reference voltage V _ref of the semiconductor integrated circuit device (1L) is smaller than the voltage value V ₂ of the reference voltage V _ref of the semiconductor integrated circuit device (1R).

In this case, the detection circuit (2L) and (2R) of each semiconductor integrated circuit device (1L) and (1R), if the level of the input audio signal respectively supplied does not exceed the respective reference voltage V _ref Control amplifier circuits (8L) and (8R) respectively Since supplying a control voltage, these semiconductor integrated circuit device voltage value V ₁ of the reference voltage V _ref of (1L), the semiconductor integrated circuit device voltage value V ₂ of the reference voltage V _ref of the (1R), a control voltage The relationship is as follows.

Therefore, the reference voltages V _ref and V of the semiconductor integrated circuit device (1L) are
_It is assumed that the voltage values V ₁ and V ₁ ′ of _ref ′ are equal and the reference voltage V _{ref of} the semiconductor integrated circuit device (1R) and the voltage values V ₂ and V _ref of V _ref ′ are
If V ₂ ′ are equal, then

First, the voltage control amplifier circuit (8L) of the semiconductor integrated circuit device (1L)
Is a control voltage larger than the voltage value V ₁ ′ of the reference voltage V _ref ′. Is supplied, the voltage control amplifier circuit (8L) lowers the gain at that time.

On the other hand, the voltage control amplifier circuit (8R) of the semiconductor integrated circuit device (1R)
Is a control voltage smaller than the voltage value V ₂ ′ of the reference voltage V _ref ′. , The voltage controlled amplifier circuit (8R) maximizes the gain.

Therefore, in this case, as shown in FIG. 7B, the characteristic of the output level with respect to the input level is the semiconductor integrated circuit device (1L).
Shows the characteristics indicated by the one-dot chain line, and the semiconductor integrated circuit device (1
In R), the characteristic is shown by the broken line. In such a case,
The correction is impossible because of the semiconductor integrated circuit device.

In such a case, the relative level difference at the time of input of the L channel and R channel audio signals changes at the time of output. Therefore, after recording this on a magnetic tape, the magnetic tape is reproduced by a reproducing system and supplied to speakers for the L channel and the R channel via an amplifier or the like to deteriorate localization. In addition to the monaural semiconductor integrated circuit device, the cost of manufacturing a stereo semiconductor integrated circuit device is high.

The present invention has been made in view of the above points, and can be commonly used for audio circuits of both monaural and stereo systems, and also provides good stereo audio when used for stereo system audio circuits. The present invention intends to propose a semiconductor integrated circuit device that can obtain the above-mentioned characteristics.

[Means for Solving the Problems]

The semiconductor integrated circuit device according to the present invention is, for example, as shown in FIGS. 1 to 4, an amplifier circuit (5) to which an input signal from an input terminal (6) is supplied, an output level of the amplifier circuit (5) and The detection circuit (2) which compares the reference level V _{ref of} 1 and outputs a control signal based on the comparison result, the level of the control signal from the detection circuit (2) and the second reference level V _ref ′. And a control current signal based on the comparison result is supplied to the amplifier circuit (5) to control the gain of the amplifier circuit (5).
And are provided.

[Action]

According to the present invention described above, the control current generation circuit (4) compares the level of the control signal from the detection circuit (2) with the first reference level V _ref, and the control current based on the comparison result. By supplying a signal to the amplifier circuit (5) so as to control the gain of the amplifier circuit (5), for example, as shown in FIG. 4A, the non-linear characteristic of the control current generation circuit (4) causes Since it is possible to absorb variations in the reference voltage V _ref ,
It can be commonly used for both monaural and stereo audio circuits, and good stereo sound can be obtained even when used for a stereo audio circuit.

〔Example〕

An embodiment of the semiconductor integrated circuit device of the present invention will be described in detail below with reference to FIG.

In FIG. 1, the monaural audio signal supplied to the audio signal input terminal (6) is supplied to the output terminal (7) through the current control amplifier circuit (5). The audio signal from the current control amplifier circuit (5) is input to the detection circuit (2) and the reference voltage V
compared with _ref . The control voltage output by this comparison is supplied to the control current generation circuit (4) through the amplifier circuit (3) and compared with the reference voltage V _ref ′ (= V _ref ). Then, a control current signal based on the result is supplied from the control current generating circuit (4) to the current control amplifier circuit (5).

The control current generating circuit (4) has a circuit configuration as shown in FIG.

In FIG. 2, T ₁ is an input terminal supplied with the control voltage from the amplifier circuit (3), and the control voltage supplied to this input terminal T ₁ is supplied to the base of the PNP transistor Q _1. .

The collector of this transistor Q ₁ is grounded and the emitter of the transistor Q ₂ is connected to the emitter of the constant current source.
Through (3a), it is connected to the power supply terminal (9) to which the positive power supply + B is supplied.

A reference voltage V _ref ′ is applied to the base of the transistor Q ₂ , and its collector is connected to the collector of a diode-connected NPN transistor Q ₃ .

The emitter of the diode-connected transistor Q ₃ is a resistor R ₁
Grounded through the base of this transistor Q ₃
Together with this, it is connected to the base of an NPN type transistor Q ₄ which constitutes a current mirror circuit (9).

The emitter of the transistor Q ₄ is grounded via the resistor R ₂ , and its collector is connected to the control current signal output terminal T ₂ connected to the gain control terminal of the current control amplifier circuit (5).

Therefore, the control voltage from the detection circuit (2) is supplied to the base of the transistor Q ₁ through the amplification circuit (buffer) (3), and the voltage of the control voltage is applied to the base of the transistor Q ₂ as a reference voltage. When the voltage is the same as V _ref ′, the differential balance between the transistors Q ₁ and Q ₂ is maintained, so that the control current signal flowing through the collector of the transistor Q ₄ is constant current source (3a).
When the current I ₀ is Becomes When the control voltage exceeds the reference voltage V _ref ′, the differential balance between the transistors Q ₁ and Q ₂ is disturbed, so that the control current signal changes according to the characteristics shown in FIG.

Further, for example, the reference voltage V _ref ′ applied to the base of the transistor Q ₂ is calculated from the control voltage (= V _ref ) in the steady state supplied from the detection circuit (2) through the amplification circuit (3). A slightly higher voltage may be set to supply the control voltage (= V _ref ). In this case [control signal (= V _ref )], a very small current flows through the collector of the transistor Q ₄ .

The semiconductor integrated circuit device that constitutes the above-mentioned AGC circuit is one in the case of a monaural audio signal recording device, but when it is used in a stereo type audio signal recording device, as shown in FIG. And R channel will be used.

In FIG. 3, the L channel audio signal input terminal (6
The L channel audio signal supplied to L) is supplied to the output terminal (7L) through the current control amplifier circuit (5L) and also to the detection circuit (2L) and compared with the reference voltage V _ref. . The control voltage based on the comparison result from the detection circuit (2L) is supplied to the control current generation circuit (4L) through the amplification circuit (3L). The control current generation circuit (4L) supplies a control current signal having a characteristic that the output power value thereof is almost unchanged to a voltage near the reference voltage V _ref ′ to the current control amplification circuit (5L).

On the other hand, the R channel audio signal supplied to the R channel audio signal input terminal (6R) is supplied to the output terminal (7R) through the current control amplifier circuit (5R) and also to the detection circuit (2R). The control voltage based on the comparison result from the detection circuit (2R) is supplied to the control current generation circuit (4R) through the amplification circuit (3R). This control current generation circuit (4R)
A control current signal having a characteristic that the output current value hardly changes in the voltage near _ref ′ is supplied to the current control amplifier circuit (5
R).

Further, the respective detection circuits (2L) and (2R) are connected to each other, and the respective control voltages are averaged by one capacitor C connected to the midpoint of the connection.

In the above-mentioned case, due to so-called variations in the semiconductor integrated circuit device, the reference voltages V _ref of the semiconductor integrated circuit devices (1L) and (1R) do not become equal to each other, so that the respective detection circuits (2L) and ( The reference voltage V _ref 'compared with the control voltage supplied from the 2R) to the control current generation circuits (4L) and (4R) through the amplifier circuits (3L) and (3R), respectively, is also different from each other. But,
The control voltages from the detection circuits (2L) and (2R) are supplied to the control current generation circuits (4L) and (4R) described in FIG. 2, respectively, and these control current generation circuits (4L) and (4R) are supplied to the control current generation circuits (4L) and (4R). These control current generating circuits (4L) and (4R) respectively output control current signals having the characteristics shown in FIG. 4, so that the reference voltage is changed depending on the characteristics of these control current signals.
It is used for stereo audio signal recording device because it absorbs the variation of V _{ref and} the gain for input level is almost uniform even if the reference voltages V _{ref of} semiconductor integrated circuit devices (1L) and (1R) vary slightly. When you do, the left and right localization is not recorded as it is different from the localization at the time of input.

As is apparent from the above, since one type of 1C can be used for both a monaural audio signal recording device and a stereo audio signal recording device, a significant cost reduction can be achieved.

〔The invention's effect〕

According to the present invention described above, by the control current generating circuit,
The level of the control signal from the detection circuit and the first reference level V
By comparing with _ref and supplying the control current signal based on the comparison result to the amplifier circuit to control the gain of the amplifier circuit, for example, as shown in FIG. Since the non-linear characteristic of can absorb this variation in the reference voltage V _ref , it can be used in common with both monaural and stereo audio circuits, and when used in a stereo audio circuit. , Good stereo sound is obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention, FIG. 2 is a circuit diagram showing a comparison circuit, and FIG. 3 is a diagram showing an example in which a semiconductor integrated circuit device according to the present invention is adapted to a stereo system. FIG. 4 is a graph, FIG. 5 is a view showing a conventional example, FIG. 6 is a view showing an example in which a conventional semiconductor integrated circuit device is adapted to a stereo system, and FIG. 7 is a graph. (1) is a semiconductor integrated circuit device (AGC circuit), (2) is a detection circuit, (4) is a control current generation circuit, (5) is an amplification circuit, and (6) is an input terminal.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Katsumi Imai 2-18 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (72) Nobuyuki Otaka 2-18th Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd.

Claims (1)

[Claims] 1. An amplifier circuit supplied with an input signal from an input terminal and a detection circuit for comparing an output level of the amplifier circuit with a first reference level and outputting a control signal based on the comparison result. And a level of the control signal from the detection circuit is compared with a second reference level, and a control current signal based on the comparison result is supplied to the amplification circuit to control the gain of the amplification circuit. A semiconductor integrated circuit device comprising a control current generating circuit.