JPH1041758A - Semiconductor integrated circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide line-out output signals of a large amplitude, a high S/N and less influence of nose during transmission by incorporating a line-out output stage in an integrated circuit for a low frequency power amplifier and operating it by a high power supply potential. SOLUTION: The IC 22 for the low frequency power amplification is incorporated in an audio equipment 21. The integrated IC 22 for the low frequency power amplification is constituted of an input amplifier stage 26, a push-pull power amplifier stage 27 and the line-out output stage 29. The line-out output stage 29 is incorporated in the integrated circuit 22 for the low frequency power amplifier and is prepared in a high breakdown strength process. Thus, the amplitude of the line-out output signals is enlarged and the S/N of the line-out output signals is raised. Further, since additional functions such as a muting function and a beep sound function, etc., are shared by a power amplifier part and a line-out output part, the cost is reduced and the space is made small.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor integrated circuit in which a low-frequency power amplifier is integrated, and more particularly to a low-frequency power amplification stage of an audio device having a line-out function such as a component stereo or a car stereo. Things.

[0002]

2. Description of the Related Art In an audio device having a line-out output, a low-frequency power amplifier which is generally called a power amplifier and drives a speaker and a low-frequency voltage amplifier which is called a line-out output are separately provided. . Usually, the power amplifier section is configured using a power IC, and the line-out output section is configured using a line amplifier IC, an operational amplifier, and the like.

FIG. 3 shows an example of a conventional audio device having a line-out function. In FIG. 3, the low-frequency power amplifying IC 1 has an audio signal input terminal, a beep sound input terminal, a mute signal input terminal, and an output terminal. An audio signal is supplied to the audio signal input terminal, and the audio signal input terminal is connected to the input terminal of the low frequency power amplifier 5. A beep sound is supplied to the beep sound input terminal, and the beep sound is supplied to the input terminal of the low frequency power amplifier 5 via the beep sound means 3 which is a buffer amplifier. Further, a mute means 4 is provided between the input terminal of the low-frequency power amplifier 5 and the ground. A mute signal is input to the mute signal input terminal, and the mute means 4 operates according to the mute signal. The power supply Vcc of the audio device 11 is supplied to the power terminal of the power amplifier 5 from within the audio device. The output terminal of the low-frequency power amplifier 5 becomes the output terminal of the low-frequency power amplification IC 1, and is connected to the audio output terminal of the audio device 11 via the coupling capacitor 9. For example, a speaker 12 is connected to the audio output terminal.

In the line-out output unit 2, a beep sound is supplied to an input terminal of the low-frequency voltage amplifier 8, and an audio signal is supplied to an input terminal of the low-frequency voltage amplifier 8 via a switch 6. Switch 6 is normally closed and opens when a beep is input. The low frequency voltage amplifier 8
It is provided to amplify an input signal having a small amplitude, such as an audio signal, to obtain a line-out output signal having a good S / N ratio. A mute means 7 which operates between an input terminal of the low frequency voltage amplifier 8 and the ground in accordance with a mute signal.
Is provided. The power supply terminal of the voltage amplifier 8 has a reference potential V
ref is supplied. The output terminal of the line-out output unit 2 becomes the output terminal of the low-frequency voltage amplifying IC 8, and is connected to the line-out output terminal of the audio device 11 via the coupling capacitor 10. The line-out output terminal of the audio device is connected to, for example, a booster amplifier or an AV amplifier via a cable 13.

[0005] In general, how much audio output an audio device can obtain is an important factor indicating the performance of the audio device. for that reason,
The low-frequency power amplifier 1 is supplied with power from a power supply line having the highest potential in the audio equipment, regardless of whether it is integrated or not, and performs a high-voltage process suitable for the highest power supply voltage to be used. It is manufactured using.

On the other hand, the use of a high breakdown voltage process increases the manufacturing cost. Therefore, in order to reduce the cost, the line-out low-frequency voltage amplifier 8 is usually manufactured using a relatively low withstand voltage process. Therefore, a reference voltage Vref lower than the power supply voltage Vcc is generated from the power supply voltage Vcc using the stabilized power supply circuit, and the reference voltage is supplied to the power supply terminal of the low-frequency voltage amplifier 8.

[0007]

As described above, since the line-out low-frequency voltage amplifier is formed by using a process with a relatively low withstand voltage in order to reduce the cost, the amplitude of the line-out output signal is limited. Occurs. As a result, the S / N ratio of the line-out output signal cannot be sufficiently obtained, and in the circuit example shown in FIG. 3, the disturbance noise 14 rides on the signal while the line-out output signal is transmitted through the cable 13. During transmission, the S / N ratio deteriorates considerably.

Further, as shown in FIG. 3, when additional functions such as a mute function and a beep sound function are incorporated in an integrated circuit for a low-frequency power amplifier, the line-out low-frequency voltage amplifier has these additional functions. Can not be used. Therefore, as shown in FIG. 3, a mute function, a beep sound amplifier, and the like must be separately provided for line out, so that the cost increases and the mounting space increases.

When a low-frequency power amplifier and a low-frequency voltage amplifier share an additional function using a low-frequency power amplifier having a built-in additional function, a line-out output signal is generated from an output signal of the low-frequency power amplifier. become. FIG.
Shows an example of a conventional audio device sharing such additional functions. Hereinafter, the same components are denoted by the same reference numerals, and description thereof will be omitted.

In FIG. 4, the low-frequency power amplifying IC 1 is the same as the IC 1 shown in FIG. The sound signal and the beep sound are supplied to the sound signal input terminal and the beep sound input terminal of the low-frequency power amplifying IC 1, respectively. The output terminal of the low-frequency power amplifying IC 1 is connected to the audio output terminal of the audio device via the coupling capacitor 9. The output terminal of the power amplifying IC1 is connected to one end of a resistor R1, and the other end of the resistor R1 is grounded via a resistor R2. The resistors R1 and R2 constitute the attenuation resistor 15. Furthermore, the connection point of the resistors R1 and R2 is connected to the low-frequency voltage amplifier 8
Is connected to the input terminal. The power supply terminal of the low-frequency voltage amplifier 8 is supplied with the reference potential Vref, and the output terminal of the voltage amplifier is connected via a coupling capacitor 10 to a line-out output terminal of the audio equipment. Thus, the low-frequency voltage amplifying means 2 is constituted by the attenuation resistor 15 and the voltage amplifier 8.

In this circuit, unlike the circuit shown in FIG. 3, it is not necessary to separately provide a circuit for additional functions such as a mute function and a beep function for line out. However, the output signal of the low-frequency power amplifier generally has a lower distortion factor and a higher noise voltage than the input signal. In the circuit shown in FIG. 4, since the output signal of the power amplifier is amplified instead of the input audio signal to obtain the line amplifier output signal, the characteristics of the line-out output signal are degraded, and the quality of the entire audio set is reduced. Will go down.

If the low-frequency voltage amplifier 8 produced by the low-breakdown-voltage process is used for cost reduction, it becomes difficult to sufficiently obtain the amplitude of the line-out output signal.
Furthermore, since the large-amplitude output signal amplified by the low-frequency power amplifier is divided by the resistors R1 and R2 and input to the line-out low-frequency voltage amplifier, it is necessary to increase the breakdown voltage of the attenuation resistors R1 and R2.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and in an audio device having a line-out function, a mute function, a beep sound function, and the like can be provided together with a power amplifier for a speaker and a line-out without deteriorating the quality of the entire set. To reduce cost and space by sharing with a voltage amplifier for
Another object is to obtain a line-out signal having a large S / N ratio.

[0014]

In order to solve the above problems, a semiconductor integrated circuit according to the present invention comprises an audio signal input terminal to which an audio signal is supplied, a mute signal input terminal to which a mute signal is supplied, and an audio signal output terminal. And a first amplifier having a line-out output terminal and receiving an audio signal;
A mute function that acts on the first amplifier in response to a mute signal, and an input terminal connected to an output terminal of the first amplifier, which outputs a power-amplified audio signal to an audio signal output terminal and uses the highest power supply A power amplifier having a withstand voltage suitable for the voltage, a voltage amplifier having an input terminal connected to the output terminal of the first amplifier, outputting a line-out signal to a line-out output terminal, and having a withstand voltage suitable for the highest power supply voltage to be used; Is provided.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a first embodiment of the present invention. In FIG. 1, an audio device 21 has a built-in low frequency power amplification IC 22. The integrated low-frequency power amplification IC 22 includes an input amplifier stage 26, a push-pull type power amplification stage 27, and a line-out output stage 29.
It consists of. Further, the low-frequency power amplification IC 22
Is provided with mute means 25 and beep sound means 23 as additional functions. The IC 22 is manufactured using a high withstand voltage process suitable for the highest power supply potential Vcc used in the audio equipment.
Is supplied as a power supply potential.

In this embodiment, the audio signal input from the audio signal input terminal is voltage-amplified by the input amplifier stage 26. The mute means 25 acts on the input amplifier stage 26 according to the mute signal. For example, the mute means is a transistor having a base to which a mute signal is supplied. When the mute signal is supplied, the mute means grounds the input terminal of the input amplifier stage 26, and the input amplifier stage 26 does not output any signal. The output signal of the input amplifier stage 26 is supplied to input terminals of a line-out output stage 29 and a push-pull power amplifier stage 27, respectively.

The beep sound supplied from the audio device is supplied to an input terminal of the beep sound means 23, and an output terminal of the beep sound means 23 is connected to an output terminal of the input amplifier stage 26. The beeping means 23 comprises an amplifier 24, and the input beeping sound is amplified by the amplifier 24 to generate a push-pull power amplifier stage 27 and a line-out output stage 29.
Is supplied to the input terminal of.

The output terminal of the push-pull type power amplification stage 27 becomes the audio signal output terminal of the low frequency power amplification IC 22, and is connected to the audio signal output terminal of the audio device 21 via the coupling capacitor 30. An audio signal output terminal of the audio device 21 is connected to, for example, the speaker 12.

The line-out output stage 29 includes, for example, a buffer 28, and is supplied with a power supply potential Vcc as a power supply. The output terminal of the input amplifier stage 26 is supplied to the input terminal of the buffer 28, and the output terminal of the buffer 28 is connected to the line-out output terminal of the low-frequency power amplification IC 22. A line-out output terminal of the low-frequency power amplification IC 22 is connected to a line-out output terminal of the audio device 21 via a coupling capacitor 31.

The buffer 28 of the line-out output stage 29
Functions to prevent interference of electrical characteristics between devices when a booster amplifier or AV amplifier is connected to the line-out output terminal. Further, the buffer 28
May be 1, but if the amplitude of the input signal of the buffer 28 does not reach an appropriate value as the line-out output, since the voltage gain of the input amplifier stage 26 is set as a buffer, for example, 28 is provided with a voltage gain to obtain a line-out output signal having an appropriate amplitude. Conversely, if the voltage gain of the input amplifier stage 26 is appropriate for a line-out output, the buffer 28 can be omitted.

In the present embodiment, the line-out output stage is built in the integrated circuit for the low-frequency power amplifier, and is formed by a high withstand voltage process. Therefore, the amplitude of the line-out output signal can be increased, and the S of the line-out output signal can be increased.
/ N ratio can be increased. Further, since the line-out output stage is formed as one chip together with the low-frequency power amplifier, even if the line-out output stage is manufactured by a high withstand voltage process, the cost hardly increases.

Further, since additional functions such as a mute function and a beep sound function are shared by the power amplifier section and the line-out output section, the cost can be reduced and the space can be reduced.

Further, since the input amplifier stage 26 is shared by the power amplifier section and the line-out output section, the space can be reduced. In the present embodiment, the mute function and the beep sound function are provided in the integrated circuit 22, but any one of them may be provided. Further, with the integrated circuit shown in FIG. 1, when a beep sound is supplied by utilizing the mute function, it is possible to mute (mute) the audio signal without adding external components.

FIG. 2 shows a second embodiment of the present invention. In the present embodiment, the present invention is applied to a BTL (Balanced Transformerless or Bridge TiedLoad) power amplifier, and a line-out signal can be output in the form of a balanced signal.

As shown in FIG. 2, an IC for amplifying low frequency power
Reference numeral 41 denotes an input amplifier stage 42, push-pull power amplification stages 46 and 47, a phase inversion amplifier 45, a line-out output stage 48, a mute means 44, and a beep sound means 43. The IC 41 is manufactured by a high withstand voltage process, and a power supply potential Vcc of an audio device is supplied as a power supply.

In this embodiment, the audio signal input from the audio signal input terminal is voltage-amplified by the input amplifier stage 42. The mute means 44 acts on the input amplifier stage 42, and operates when the mute means operates in response to a mute signal supplied to the mute signal input terminal.
2 does not output any signal.

The beep sound supplied from inside the audio device is supplied to an input terminal of the beep sound means 43, and an output terminal of the beep sound means 43 is connected to an output terminal of the input amplifier stage 42. The beep sound means 43 includes an amplifier 52, and the input beep sound is amplified by the amplifier 52 and output.

Further, the output signal of the input amplifier stage 42 and the output signal of the beep sound unit 43 are input to a phase inversion amplifier 45. The phase inversion amplifier 45 divides the input signal into a signal having the same phase as the input signal and a signal having the opposite phase, and outputs the signal. The audio signal in phase with the input signal is supplied to the input terminal of the push-pull power amplification stage 46, and the output terminal of the push-pull power amplification stage 46 becomes the in-phase audio signal output terminal of the low-frequency power amplification IC 41. A signal having a phase opposite to that of the input signal is supplied to an input terminal of the push-pull type power amplifying stage 47, and an output terminal of the push-pull type power amplifying stage 47 is a negative-phase audio signal output terminal of the low-frequency power amplifying IC 41. Becomes

The output signal of the phase inverting amplifier 45 is
It is also supplied to the input terminal of the line-out output stage 48. The line-out output stage 48 includes a common-mode signal voltage amplifier 49,
It is constituted by a voltage amplifier 50 for a reverse phase signal. The in-phase signal output from the phase inversion amplifier 45 is supplied to the input terminal of the in-phase signal voltage amplifier 49, and the in-phase signal voltage amplifier 49
Are the common-mode line-out output terminals.
Similarly, the negative-phase signal output from the phase inversion amplifier 45 is supplied to the input terminal of the negative-phase signal voltage amplifier 50, and the output terminal of the negative-phase signal voltage amplifier 50 becomes a negative-phase signal line-out output terminal. Thus, the line-out output stage 48
Outputs the line-out output signal as a balanced signal.
If the line-out output signal is output in the form of a balanced signal, it is less likely to be affected by disturbance noise in the signal transmission process, and is used for high-quality audio equipment and studio technology.

In the present embodiment, the line-out output stage is built in the integrated circuit for the low-frequency power amplifier, is formed by a high withstand voltage process, and operates at the power supply potential Vcc. for that reason,
The amplitude of the line-out output signal can be increased,
The S / N ratio of the line-out output signal can be increased. Further, since the line-out output stage is formed as one chip together with the low-frequency power amplifier, the mounting space can be reduced, and even if the line-out output stage is manufactured by a high breakdown voltage process, the cost hardly increases.

Further, since additional functions such as a mute function and a beep sound function and an input amplifier stage are shared by the power amplifier section and the line-out output stage, costs can be reduced and space can be saved. Further, since the line-out output signal and the audio signal are output as a balanced signal, the output signal is less likely to be affected by disturbance noise in the signal transmission process.

[0032]

As described above, according to the present invention,
The line-out output stage is built in the integrated circuit for the low-frequency power amplifier manufactured by the high withstand voltage process and operated at a high power supply potential, so that the amplitude is large, the S / N ratio is high, and the influence of noise during transmission is small. A line-out output signal can be obtained, cost can be reduced, and mounting space can be reduced.

According to the present invention, the additional function provided in the low-frequency power amplifier can be used in the line-out output stage without deteriorating the quality of the line-out output signal.
It is possible to reduce the cost of the entire audio device and save space.

[Brief description of the drawings]

FIG. 1 is a diagram showing a first embodiment of the present invention.

FIG. 2 is a diagram showing a second embodiment of the present invention.

FIG. 3 is a diagram showing a conventional example.

FIG. 4 is a diagram showing a conventional example.

[Explanation of symbols]

 12, 51 ... speaker, 11, 21 ... audio equipment, 22, 41 ... integrated circuit, 23, 43 ... beep means, 24, 52 ... amplifier, 25, 44 ... mute means, 26, 42 ... input amplifier stage, 27 , 46, 47: push-pull power amplification stage, 28: buffer amplifier, 29, 48: line-out output stage, 30, 31: coupling capacitor 45: phase inversion amplifier 49, 50: voltage amplifier.

Claims (5)

[Claims] An audio signal input terminal to which an audio signal is supplied, a mute signal input terminal to which a mute signal is supplied,
A first amplifier having an audio signal output terminal and a line-out output terminal, to which the audio signal is input; a mute function to which the mute signal is input, which acts on the first amplifier; A power amplifier connected to an output terminal of the first amplifier, outputting a power-amplified audio signal to the audio signal output terminal, and having a withstand voltage suitable for the highest power supply voltage to be used; Output terminal, and outputs a line-out signal to the line-out output terminal,
A semiconductor integrated circuit comprising: a voltage amplifier having a withstand voltage suitable for the highest power supply voltage to be used. 2. An audio signal input terminal to which an audio signal is supplied, a mute signal input terminal to which a mute signal is supplied,
An audio signal output terminal, and a line-out output terminal, an audio signal input from the audio signal input terminal is input, and a power-amplified audio signal is output to the audio signal output terminal; A power amplifier having a withstand voltage suitable for a voltage, an audio signal input from the audio signal input terminal being supplied, outputting a line-out signal to the line-out output terminal, and a voltage having a withstand voltage suitable for the highest power supply voltage to be used A semiconductor integrated circuit comprising: an amplifier; and a mute circuit connected to the audio signal input terminal and muting the audio signal input to the power amplifier and the voltage amplifier according to the mute signal. 3. The semiconductor integrated circuit according to claim 1, further comprising a beeping means for supplying a beeping sound to input terminals of said power amplifier and said voltage amplifier. 4. The semiconductor integrated circuit according to claim 1, wherein said voltage amplifier is a buffer amplifier. 5. The semiconductor integrated circuit according to claim 1, wherein said power amplifier is a BTL type amplifier.