JP2003087064A - Amplifier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a balanced output type stereo amplifier which will not be damaged, even if it is connected to a three-terminal headphone. SOLUTION: The balanced output type stereo amplifier is provided with an operational amplifier 1 for applying non-reverse amplification to an input signal SL and output it, an operational amplifier 2 for applying reverse amplification to the signal SL and for outputting it, an operational amplifier 3 for applying non-reverse amplification to an input signal SR and output it, and an operational amplifier 4 for subjecting the signal SR to reverse amplification and output it, where the amplifier 2 is connected to a negative phase output terminal 10 via a resistor R1, having a resistance value which is identical to that of a voice coil resistance component R3 of the headphone, and the amplifier 4 is connected to the negative phase output terminal 12 via a resistor R2, having a resistance value identical to that of a voice coil resistance component R4 of the headphone.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an amplifier that outputs an audio signal.

[0002]

2. Description of the Related Art Most of the amplifiers of audio equipment currently on the market are analog amplifiers that amplify and output analog signals. The structure of a typical analog amplifier is shown in FIG. The inverting input terminal of the operational amplifier 23 is grounded via the resistor R5 and is connected to the output terminal of the operational amplifier 23 via the resistor R6. Operational amplifier 2
The power supply voltage V _CC is supplied to 3. Then, the analog audio signal V _i input to the non-inverting input terminal of the operational amplifier 23 is amplified and output.

[0003] analog amplifier of FIG. 6 is applied with negative feedback, even when the power supply voltage V _CC is varied by this negative feedback, that variations in the power supply voltage V _CC is to reduce the effect on the output voltage V _O it can. Therefore, the power supply voltage V _CC
Fluctuations of sound quality have less adverse effects on sound quality. Further, the connection node between the output terminal of the operational amplifier 23 and the resistor R6 is connected to the output terminal 24 via the coupling capacitor C1.
The coupling capacitor C1 removes the DC component of the output signal of the operational amplifier 23. That is, the coupling capacitor C1 removes the low frequency component due to the fluctuation of the power supply voltage V _CC included in the output signal of the operational amplifier 23.

As described above, most of the amplifiers of audio equipment on the market are analog amplifiers, but it is considered that digital amplifiers will be replaced by analog amplifiers in the future.

For example, in the electric circuit of the MD reproducing apparatus, all circuits that can be digitized are composed of digital circuits. The only circuits that have not been digitized at present are amplifiers that output audio signals to audio output means such as headphones. In other words, this amplifier is the only analog circuit. If this amplifier is digitized, all the circuits become digital circuits, the manufacture of the MD reproducing device LSI is simplified, and the cost of the MD reproducing device can be reduced.

[0006]

However, when amplifying a digital signal, negative feedback cannot be applied because the input signal is a digital signal. Therefore, in the digital amplifier, when the power supply voltage V _CC fluctuates, the influence of the fluctuation _directly affects the output signal, and the sound quality deteriorates.

In view of the above problems, it is a first object of the present invention to provide a digital amplifier which is not affected by fluctuations in power supply voltage.

Further, when a digital amplifier which is not affected by the fluctuation of the power supply voltage is realized by means which will be described later, four output terminals are required for two-channel stereo output. When connecting headphones to an amplifier having such four output terminals, four-terminal headphones having a plug composed of four terminals 28, 29, 30, and 31 as shown in FIG. 7 are used.

However, in the market, there is a 3 having a plug composed of three terminals 32, 33 and 34 as shown in FIG.
Most of the headphones are terminal headphones. Therefore, it is desirable to be able to use three-terminal headphones.

However, if the three-terminal headphone is connected to a digital amplifier having the above-mentioned four output terminals and not affected by the fluctuation of the power supply voltage, the digital amplifier will be damaged or a large crosstalk will occur. Similarly, even in a balanced output type analog amplifier that outputs two channels of stereo type, if three-terminal headphones are connected, the analog amplifier will be damaged or large crosstalk will occur.

In view of the above problems, it is a second object of the present invention to provide a balanced output type amplifier which outputs two channels of stereo type without being damaged even when connected to three terminal headphones.

[0012]

In order to achieve the above first object, in a digital amplifier according to the present invention,
A positive phase amplifying means for non-inverting and amplifying the input signal and outputting, a negative phase amplifying means for inverting and amplifying the input signal and outputting, and a first output terminal connected to the output side of the positive phase amplifying means, A second output terminal connected to the output side of the negative phase amplifying means, wherein the positive phase amplifying means and the negative phase amplifying means receive the same input signal, and the same input signal is binary. It is a quantized signal.

In order to achieve the second object, in the amplifier according to the present invention, first positive phase amplifying means and second positive phase amplifying means for non-inverting amplifying an input signal and outputting the non-inverted signal,
A first anti-phase amplifying means and a second anti-phase amplifying means for inverting and amplifying an input signal and outputting the same; a first positive-phase output terminal connected to an output side of the first positive-phase amplifying means; A second positive phase output terminal connected to the output side of the second positive phase amplification means, and a first positive phase output terminal connected to the output side of the first negative phase amplification means.
A negative-phase output terminal and a second negative-phase output terminal connected to the output side of the second negative-phase amplifying means, the first positive-phase amplifying means and the first negative-phase amplifying means being provided. Means inputs the first input signal, the second positive phase amplification means and the second negative phase amplification means input the second input signal, and the first positive phase amplification means and the first The positive-phase output terminal is connected via the first resistor, and the second positive-phase amplifying means and the second positive-phase output terminal are connected via the second resistor. Alternatively, the first signal that non-inverts and amplifies the input signal and outputs
Of the positive phase amplifying means and the second positive phase amplifying means, the first negative phase amplifying means and the second negative phase amplifying means for inverting and amplifying the input signal and outputting the inverted signal, and the first positive phase amplifying means. A first positive-phase output terminal connected to the output side, a second positive-phase output terminal connected to the output side of the second positive-phase amplification means, and the first
A first anti-phase output terminal connected to the output side of the anti-phase amplification means and a second anti-phase output terminal connected to the output side of the second anti-phase amplification means. One positive phase amplification means and the first negative phase amplification means input the first input signal, and the second positive phase amplification means and the second negative phase amplification means input the second input signal. However, the first anti-phase amplification means and the first anti-phase output terminal are connected via a first resistor, and the second anti-phase amplification means and the second anti-phase output terminal are connected. The connection is made via the second resistance means.

The first input signal and the second input signal may be binary quantized signals.

Further, the first resistor and the second resistor may be variable resistors.

Further, each of the first resistor and the second resistor may be a resistance means comprising a plurality of resistances and a switching means for switching a connection state of the plurality of resistances.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described with reference to the drawings. First, the digital amplifier according to the first embodiment of the present invention will be described. The structure of the digital amplifier of the first embodiment is shown in FIG.

The terminal to which the binary quantized signal S1 is input is connected to the terminal 16a of the switch circuit 16. The terminal to which the analog audio signal S2 is input is connected to the terminal 16b of the switch circuit 16 via the delta-sigma modulation circuit 13.
Connected to. Further, the 16-bit digital signal S3 is connected to the terminal 16c of the switch circuit 16 via the interpolation circuit 14 and the delta-sigma modulation circuit 15.

The terminal 16d of the switch circuit 16 is connected to the non-inverting input terminal of the operational amplifier 17 and the inverting input terminal of the operational amplifier 18. The inverting input terminal of the operational amplifier 17 and the non-inverting input terminal of the operational amplifier 18 are grounded.

The output terminal of the operational amplifier 17 is connected to the positive phase output terminal 21 via the low-pass filter 19 composed of a resistor and a capacitor. The output terminal of the operational amplifier 18 has a low-pass filter 20 including a resistor and a capacitor.
Is connected to the negative-phase output terminal 22 via.

The operation of the digital amplifier of the first embodiment having such a configuration will be described. The analog audio signal S2 is converted into 2 by the delta-sigma modulation circuit 13.
Value is converted to a quantized signal. Further, the 16-bit digital signal is converted by the interpolation circuit 14 into, for example, a 32-bit digital signal having a sine pulling frequency which is N times the original sampling frequency. The 32-bit digital signal is converted into a binary quantized signal by the delta sigma modulation circuit 15. Therefore, the signals input to the terminals 16a, 16b, and 16c of the switch circuit 16 are all binary quantized signals.

The switch circuit 16 selects one of the terminals 16a to 16c according to a control signal from a control circuit (not shown) and connects it to the terminal 16d. This gives 2
The value quantized signal is input to the operational amplifiers 17 and 18.

Here, the binary quantized signal input to the operational amplifiers 17 and 18 is S [V], the gain of the operational amplifiers 17 and 18 is A, and the power supply voltage of the operational amplifiers 17 and 18 is V _CC [ V], and the fluctuation of the power supply voltage of the operational amplifiers 17 and 18 is ΔV _CC [V]. Further, the operational amplifiers 17 and 18 perform voltage level shift so that the reference potential of the output signal becomes half of the power supply voltage.

Since the operational amplifier 17 non-inverts and amplifies the binary quantized signal and outputs it, the output signal of the operational amplifier 17 is A
× S + (V _CC + ΔV _CC ) / 2 [V]. On the other hand, since the operational amplifier 18 non-inverts and amplifies the binary quantized signal and outputs it, the output signal of the operational amplifier 18 is A × (−S) + (V _CC
+ ΔV _CC ) / 2 [V].

The low-pass filter circuit 19 removes high frequency components of the output signal of the operational amplifier 17,
Only the audible range component of the output signal of is output to the positive phase output terminal 21. Further, the low-pass filter circuit 20 removes a high frequency component of the output signal of the operational amplifier 18,
Only the audible range component of the output signal of is output to the negative phase output terminal 22.

Since the voltage drop in the low-pass filter circuits 19 and 20 is very small, it is considered that there is no voltage drop. Then, the voltage between the positive-phase output terminal 21 and the negative-phase output terminal is {A × S + (V _CC + ΔV _CC ) / 2} − {A
× (−S) + (V _CC + ΔV _CC ) / 2} [V], and A ×
It becomes 2S [V]. Therefore, the audio signal output by the digital amplifier is not affected by the fluctuation of the power supply voltage. Of course, the coupling capacitor provided in the conventional analog amplifier (see FIG. 6) is not required.

Next, the amplifier of the first embodiment described above is
A case where the present invention is applied to a channel stereo amplifier will be described with reference to FIG. The stereo amplifier of FIG. 3 inputs a binary quantized signal S _L which is a left channel input signal and a binary quantized signal S _R which is a right channel input signal.

The terminal to which the binary quantized signal S _L is input is connected to the non-inverting input terminal of the operational amplifier 1 and the inverting input terminal of the operational amplifier 2. The inverting input terminal of the operational amplifier 1 and the non-inverting input terminal of the operational amplifier 2 are grounded.

The output terminal of the operational amplifier 1 is connected to the left channel positive phase output terminal 9 via a low pass filter 5 composed of a resistor and a capacitor. The output terminal of the operational amplifier 2 is connected to the left channel negative phase output terminal 10 via the low-pass filter 6 including a resistor and a capacitor.

The terminal to which the binary quantized signal S _R is input is connected to the non-inverting input terminal of the operational amplifier 3 and the inverting input terminal of the operational amplifier 4. The inverting input terminal of the operational amplifier 3 and the non-inverting input terminal of the operational amplifier 4 are grounded.

The output terminal of the operational amplifier 3 is connected to the right channel positive phase output terminal 11 via a low pass filter 7 composed of a resistor and a capacitor. The output terminal of the operational amplifier 4 has a low-pass filter 8 including a resistor and a capacitor.
Is connected to the right channel reverse phase output terminal 12 via.

The stereo amplifier having such a structure operates as follows. First, the left channel side will be described.
Since the operational amplifier 1 non-inverts and amplifies and outputs the binary quantized signal S _L , the output signal of the operational amplifier 1 is A × S _L + (V
It becomes _CC + ΔV _CC ) / 2 [V]. On the other hand, the operational amplifier 2 is 2
Since the value quantized signal S _L is inverted and amplified and output, the output signal of the operational amplifier 2 is A × (−S _L ) + (V _CC + ΔV _CC ).
It becomes / 2 [V].

The low pass filter circuit 5 includes an operational amplifier 1
The high frequency component of the output signal of is removed and only the audible range component of the output signal of the operational amplifier 1 is output to the left channel positive phase output terminal 9. Further, the low-pass filter circuit 6 removes the high frequency component of the output signal of the operational amplifier 2 and outputs only the audible component of the output signal of the operational amplifier 2 to the left channel anti-phase output terminal 10.
Output to.

Since the voltage drop in the low-pass filter circuits 5 and 6 is very small, it is considered that there is no voltage drop. Then, the output signal S _{L +} of the left channel positive phase output terminal 9 becomes A × S _L + (V _CC + ΔV _CC ) / 2 [V], and the output signal S _L- of the left channel negative phase output terminal 10 is A ×. (-
S _L ) + (V _CC + ΔV _CC ) / 2 [V].

Therefore, the left channel output audio signal
Issue (S_{L +}-S_L-) Is {A × S_L+ (V_CC+ ΔV_CC) /
2}-{Ax (-S_L) + (V_CC+ ΔV_CC) / 2} [V]
Yes, A x 2S_LIt becomes [V]. This allows the left channel output
Input audio signal is immune to power supply voltage fluctuations
It Here, the output signal S of the left channel positive phase output terminal 9 _{L +}
And the output signal S of the left channel negative phase output terminal 10_L-Voltage
An example of the waveform is shown in FIG. The broken line in the figure is the reference potential.
And its value is (V_CC+ ΔV_CC) / 2 [V].

Next, the right channel side will be described. Since the operational amplifier 3 non-inverts and amplifies and outputs the binary quantized signal S _R , the output signal of the operational amplifier 3 is A × S _R + (V _CC
+ ΔV _CC ) / 2 [V]. On the other hand, since the operational amplifier 4 inverts and amplifies the binary quantized signal S _R and outputs it, the output signal of the operational amplifier 4 is A × (−S _R ) + (V _CC + ΔV _CC ) /
It becomes 2 [V].

The low pass filter circuit 7 includes an operational amplifier 3
Of the output signal of the operational amplifier 3 is output to the right channel positive phase output terminal 11. The low-pass filter circuit 8 removes the high frequency component of the output signal of the operational amplifier 4 and outputs only the audible component of the output signal of the operational amplifier 4 to the right channel anti-phase output terminal 1.
Output to 2.

Since the voltage drop in the low pass filter circuits 7 and 8 is very small, it is considered that there is no voltage drop. Then, the output signal S _{R +} of the right channel positive phase output terminal 11 becomes A × S _R + (V _CC + ΔV _CC ) / 2 [V], and the output signal S _R- of the right channel negative phase output terminal 12 is A × (-S
_R ) + (V _CC + ΔV _CC ) / 2 [V].

Therefore, the right channel output audio signal (S _{R +} -S _R- ) is {A × S _R + (V _CC + ΔV _CC ) /
2} − {A × (−S _R ) + (V _CC + ΔV _CC ) / 2} [V], which is A × 2 S _R [V]. As a result, the right channel output audio signal is not affected by the fluctuation of the power supply voltage. Here, the output signal S of the right channel positive phase output terminal 11
FIG. 4 shows an example of the voltage waveforms of the output signal S _R- of the _{R +} and right channel negative phase output terminal 12. The broken line in the figure is the reference potential, and its value is (V _CC + ΔV _CC ) / 2 [V].

Then, 4-terminal headphones are connected to the output terminals of the stereo amplifier shown in FIG. Therefore,
One end of the resistor R3, which is the resistance component of the left-channel voice coil of the stereo headphones, is connected to the left-channel positive-phase output terminal 9, and the other end of the resistor R3 is connected to the left-channel negative-phase output terminal 10. One end of the resistor R4, which is the resistance component of the right channel voice coil, is connected to the right channel positive phase output terminal 11, and the other end of the resistor R4 is connected to the right channel negative phase output terminal 12.

A × 2S _L [V] is applied to both ends of the resistor R3, and a sound pressure corresponding to the left channel output audio signal of A × 2S _L [V] is generated from the left channel voice coil. Moreover, A × 2S _R [V] is applied to both ends of the resistor R4,
A sound pressure corresponding to the right channel output audio signal of A × 2S _R [V] is generated from the right channel voice coil.

In this way, when connecting the four-terminal headphones to the stereo amplifier of FIG. 3, no problem occurs. However, when three-terminal headphones are connected to the stereo amplifier of FIG. 3, the left channel positive phase output terminal 9 and the right channel positive phase output terminal 11 are connected or the left channel negative phase output terminal 10 and the right channel negative phase output are connected. The terminal 12 will be connected. In the following description, when three-terminal headphones are connected, the left channel negative phase output terminal 10 and the right channel negative phase output terminal 12 are connected.

The output signal S of the left channel negative phase output terminal 10
_The voltage value of the _L- and the output signal S _{R- of the} right channel negative phase output terminal 12 is different (see FIG. 4). Further, usually, the output resistance of the amplifier that outputs the audio signal to the sound output means such as headphones may be considered to be substantially zero.

Therefore, the left channel reverse phase output terminal 10
And the right channel negative phase output terminal 12 are connected, the left channel negative phase output terminal 10 and the right channel negative phase output terminal 12 are connected.
A large short-circuit current will flow between and, and in the worst case, the amplifier will be damaged. Even if the amplifier is not damaged, a large crosstalk is generated because an intermediate level signal is generated between the output signal S _{L- of the} left channel negative phase output terminal 10 and the output signal S _R- of the right channel negative phase output terminal 12. Will occur.

Therefore, in the amplifier of the second embodiment according to the present invention, a stereo amplifier which does not cause a problem even if headphones with three terminals are connected is realized. The amplifier of the second embodiment is shown in FIG. The same parts as those in FIG. 3 are designated by the same reference numerals and the description thereof will be omitted.

A resistor R1 is provided between the low pass filter 6 and the left channel negative phase output terminal 10, and the low pass filter 8 is provided.
A resistor R2 is provided between the output terminal 12 and the right channel negative phase output terminal 12. The resistance value of the resistor R1 is made equal to that of the resistor R3, and the resistance value of the resistor R2 is made equal to that of the resistor R4.

Since the three-terminal headphones are connected to the amplifier of the second embodiment, the left channel negative phase output terminal 10 and the right channel negative phase output terminal 12 are connected.

The voltage waveforms of the signals S _{L +} , S _L- , S _{R +} , and S _R- output from the output terminals of the amplifier of the second embodiment, the voltage waveform of the output signal S _L- 'of the low-pass filter 6, and The voltage waveform of the output signal S _R- 'of the low pass filter 8 is shown in FIG.
Shown in. The broken line in the figure is the reference potential, and its value is (V _CC + ΔV _CC ) / 2 [V].

Output signal S of the left channel positive phase output terminal 9_{L +}
And the output signal S of the low-pass filter 6 _L-’Is in phase with each other
Are signals that differ by 180 °. Also, the resistance value of the resistor R1
And the resistance value of the resistor R3 are equal, so the left channel reverse phase output
The potential of the terminal 10 is the same as the left channel positive phase output terminal 9
It becomes an intermediate potential with the output side of the filter 6. According to
The output signal S of the left channel negative phase output terminal 10_L-Is (V
_CC+ ΔV_CC) / 2 [V].

Output signal S from the right channel positive phase output terminal 11
_{R +} and the output signal S _{R-'of the} low pass filter 8 are signals whose phases are different from each other by 180 °. Since the resistance value of the resistor R2 is equal to the resistance value of the resistor R4, the potential of the right channel negative phase output terminal 12 becomes an intermediate potential between the right channel positive phase output terminal 11 and the output side of the low pass filter 8. Therefore, the output signal S _R- of the right channel negative phase output terminal 12 becomes (V _CC + ΔV _CC ) / 2 [V].

Since the potential of the left channel anti-phase output terminal 10 and the potential of the right channel anti-phase output terminal 12 are equal, even if the left channel anti-phase output terminal 10 and the right channel anti-phase output terminal 12 are connected, the amplifier is damaged. And there is no risk of crosstalk.

The left channel output audio signal (S
_{L +} −S _L− ) becomes A × S _L [V], and the right channel output audio signal (S _{R +} −S _R− ) becomes A × S _R [V]. Therefore, the amplifier of the second embodiment is an amplifier that is not affected by the fluctuation of the power supply voltage, like the amplifier of the first embodiment.
As a matter of course, no problem occurs even if the 4-terminal headphones are connected.

If the resistance value of the resistor R1 is not equal to the resistance value of the resistor R3, or if the resistance value of the resistor R2 is not equal to the resistance value of the resistor R4, the left channel reverse phase output terminal 1
The potential of 0 and the potential of the right channel negative phase output terminal 12 do not match. In this case, a short circuit current flows between the left channel negative phase output terminal 10 and the right channel negative phase output terminal 12. However, the potential difference between the left channel negative-phase output terminal 10 and the right channel negative-phase output terminal 12 can be made smaller than that of the amplifier shown in FIG. Further, the crosstalk becomes smaller than that of the amplifier shown in FIG.

Resistors R1 and R2 of the amplifier of the second embodiment
May be a variable resistance. If the resistors R1 and R2 are variable resistors, the resistance values of the resistors R3 and R4 that differ depending on the type of the three-terminal headphones can be dealt with. Therefore, the potential of the left-channel negative-phase output terminal 10 and the right-channel negative-phase output terminal 1 is irrespective of the type of three-terminal headphones.
The potential of 2 can be made equal, and the occurrence of crosstalk can be prevented.

Further, a configuration is provided in which a plurality of resistors and a switching circuit that switches the connection state of those resistors are provided instead of the resistor R1, and a switching circuit that switches the plurality of resistors and the connection state of those resistors is provided instead of the resistor R2. Also has the same effect as the configuration in which the resistors R1 and R2 are variable resistors. As one embodiment of this configuration, a plurality of resistors having resistance values corresponding to the resistance values of the resistors R3 and R4 that differ depending on the type of three-terminal headphones are provided, and the switching circuit selectively selects one resistor from the plurality of resistors. And a mode in which a plurality of resistors having the same resistance value are provided and the switching circuit switches the number of resistors connected in parallel to change the resistance value of the combined resistance.

Although the amplifier of the second embodiment described above has a configuration in which a resistor is provided on the negative phase side, a configuration may be provided in which a resistor is provided on the positive phase side. In the case of a configuration that provides a resistor on the positive phase side,
Left channel positive phase output terminal provided on the jack of the amplifier connected to the headphone plug so that the left channel positive phase output terminal and the right channel positive phase output terminal are connected when three-terminal headphones are connected The positions of the channel negative phase output terminal, the right channel positive phase output terminal, and the right channel negative phase output terminal are determined.

The amplifier of the second embodiment described above has two
Although it is a digital amplifier for inputting a value-quantized signal, it may be in the form of an analog amplifier for inputting an analog audio signal. Also when inputting an analog audio signal, the same effect as when inputting a binary quantized signal is obtained.

[0058]

According to the present invention, the positive phase amplifying means for non-inverting amplifying the input signal and outputting it, the negative phase amplifying means for inverting amplifying the input signal and outputting the same, and the output side of the positive phase amplifying means. A first output terminal and a second output terminal connected to the output side of the negative phase amplifying means, and the positive phase amplifying means and the negative phase amplifying means both receive the same binary quantized signal. Therefore, it is possible to realize a digital amplifier in which the output audio signal, which is the voltage between the first output terminal and the second output terminal, is not affected by the power supply voltage. As a result, good sound quality can be obtained. Further, it becomes easy to manufacture an integrated circuit including this digital amplifier and other digital circuits provided in the audio equipment, and the cost of the audio equipment can be reduced.

Further, according to the present invention, the first positive phase amplification means and the second positive phase amplification means, the first negative phase amplification means and the second negative phase amplification means, and the first positive phase amplification means. A first positive phase output terminal connected to the output side of the means, a second positive phase output terminal connected to the output side of the second positive phase amplification means, and an output side of the first negative phase amplification means A first negative phase output terminal connected to the first negative phase output terminal and a second negative phase output terminal connected to the output side of the second negative phase amplification means. The negative phase amplifying means inputs the first input signal, the second positive phase amplifying means and the second negative phase amplifying means input the second input signal, and the first positive phase amplifying means and the first positive phase amplifying means. Positive phase output terminal is the first
Since the second positive phase amplifying means and the second positive phase output terminal are connected via the second resistor,
When the first positive-phase output terminal and the first negative-phase output terminal are connected via the voice coil of the headphone, the potential of the first positive-phase output terminal is changed to the output signal of the first positive-phase amplifying means and the second signal. It is possible to set it to a level near the intermediate level of the output signal of the negative phase amplification means of No. 1, and when the second positive phase output terminal and the second negative phase output terminal are connected via the voice coil of the headphones, The potential of the positive-phase output terminal can be near the intermediate level between the output signal of the second positive-phase amplifier and the output signal of the second negative-phase amplifier. Accordingly, even if the first positive-phase output terminal and the second positive-phase output terminal are connected by connecting the three-terminal headphones, the first positive-phase output terminal and the second positive-phase output terminal are connected to each other. It is possible to reduce the potential difference of. Therefore, damage to the amplifier can be prevented and crosstalk can be reduced. Also, the first resistance and the second
If the resistance value of each of the resistors is the same as the resistance value of the resistance component of the voice coil of the connected headphone, the occurrence of crosstalk can be prevented.

According to the present invention, the first positive phase amplifying means and the second positive phase amplifying means, the first negative phase amplifying means and the second negative phase amplifying means, and the first positive phase amplifying means. A first positive phase output terminal connected to the output side of the means, a second positive phase output terminal connected to the output side of the second positive phase amplification means, and an output side of the first negative phase amplification means A first negative phase output terminal connected to the first negative phase output terminal and a second negative phase output terminal connected to the output side of the second negative phase amplification means. The anti-phase amplifying means inputs the first input signal, the second normal-phase amplifying means and the second anti-phase amplifying means input the second input signal, and the first anti-phase amplifying means and the first anti-phase amplifying means The reverse phase output terminal is the first
And the second anti-phase amplifying means and the second anti-phase output terminal are connected via the second resistance means. Therefore, the first positive-phase output terminal and the first anti-phase output terminal are connected. When the phase output terminal is connected via the voice coil of the headphones, the potential of the first negative phase output terminal is set to the output signal of the first positive phase amplifying means and the first signal.
Of the output signal of the anti-phase amplifier means of the second phase, and when the second positive-phase output terminal and the second anti-phase output terminal are connected via the voice coil of the headphones,
The potential of the negative-phase output terminal of can be made to be near the intermediate level between the output signal of the second positive-phase amplifying means and the output signal of the second negative-phase amplifying means. Thereby, even if the first negative-phase output terminal and the second negative-phase output terminal are connected by connecting the three-terminal headphones, the first negative-phase output terminal and the second negative-phase output terminal are connected.
It is possible to reduce the potential difference between the negative-phase output terminal and the negative-phase output terminal.
Therefore, damage to the amplifier can be prevented and crosstalk can be reduced. Further, when the resistance values of the first resistor and the second resistor match the resistance value of the resistance component of the voice coil of the connected headphones, it is possible to prevent the occurrence of crosstalk.

Further, according to the present invention, since the first input signal and the second input signal are binary quantized signals, they are digital amplifiers. As a result, it becomes easy to manufacture an integrated circuit including this digital amplifier and other digital circuits provided in the audio device, and the cost of the audio device can be reduced.

Further, according to the present invention, since the first resistor and the second resistor are variable resistors, the resistance values of the first resistor and the second resistor are respectively set to the voice of the three-terminal headphone to be connected. It can be made to match the resistance value of the resistance component of the coil. This makes it possible to prevent the occurrence of crosstalk.

Further, according to the present invention, the first resistance and the second resistance are resistance means each comprising a plurality of resistances and a switching means for switching the connection state of the plurality of resistances. The resistance values of the resistance and the second resistance can be matched with the resistance values of the resistance components of the voice coils of the three-terminal headphones that are respectively connected. This makes it possible to prevent the occurrence of crosstalk.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an amplifier according to a second embodiment of the present invention.

FIG. 2 is a diagram showing a voltage waveform of a signal output from the output terminal of the amplifier of FIG.

FIG. 3 is a diagram showing a configuration when the amplifier of FIG. 5 is applied to a stereo amplifier.

FIG. 4 is a diagram showing a voltage waveform of a signal output from the output terminal of the amplifier of FIG.

FIG. 5 is a diagram showing a configuration of an amplifier according to the first embodiment of the present invention.

FIG. 6 is a diagram showing a configuration of a conventional analog amplifier.

FIG. 7 is a diagram showing a plug of four-terminal headphones.

FIG. 8 is a diagram showing a plug of three-terminal headphones.

[Explanation of symbols]

1-4, 17, 18 Operational amplifier 9 Left channel positive phase output terminal 10 Left channel negative phase output terminal 11 Right channel positive phase output terminal 12 Right channel negative phase output terminal 21 Positive phase output terminal 22 Reverse phase output terminals R1 to R4 Resistors S1, S _L , S _R Binary quantized signal S2 Analog audio signal S3 16-bit digital signal

Continued front page    F term (reference) 5J069 AA02 AA22 AA24 CA04 CA52                       CA56 CA87 FA15 HA25 HA29                       HA38 KA01 KA42 KA53 KA61                       KA63 MA11 SA06 TA01 TA06                 5J090 AA02 AA22 AA24 CA04 CA52                       CA56 CA87 FA15 HA25 HA29                       HA38 KA01 KA42 KA53 KA61                       KA63 MA11 SA06 TA01 TA06                 5J092 AA02 AA22 AA24 CA04 CA52                       CA56 CA87 FA15 HA25 HA29                       HA38 KA01 KA42 KA53 KA61                       KA63 MA11 SA06 TA01 TA06                       VL08                 5J500 AA02 AA22 AA24 AC04 AC52                       AC56 AC87 AF15 AH25 AH29                       AH38 AK01 AK42 AK53 AK61                       AK63 AM11 AS06 AT01 AT06                       LV08

Claims (6)

[Claims] 1. A positive phase amplifying means for non-inverting amplifying an input signal and outputting the same, a negative phase amplifying means for inverting amplifying the input signal and outputting the same, and a first side connected to an output side of the positive phase amplifying means. A second output terminal connected to the output terminal of the negative phase amplification means
And a positive-phase amplifying means and a negative-phase amplifying means both input the same input signal, and the same input signal is a binary quantized signal. 2. A first positive phase amplifying means and a second positive phase amplifying means for non-inverting amplifying an input signal, and a first negative phase amplifying means and a second positive phase amplifying means for inverting and amplifying the input signal. Two negative phase amplification means, a first positive phase output terminal connected to the output side of the first positive phase amplification means, and a second positive phase output terminal connected to the output side of the second positive phase amplification means. A positive phase output terminal, a first negative phase output terminal connected to the output side of the first negative phase amplification means, and a second negative phase output terminal connected to the output side of the second negative phase amplification means.
A negative-phase output terminal, the first positive-phase amplification means and the first negative-phase amplification means input a first input signal, and the second positive-phase amplification means and the second The negative phase amplifying means inputs the second input signal, the first positive phase amplifying means and the first positive phase output terminal are connected via a first resistor, and the second positive phase amplifying means is connected. An amplifier characterized in that the means and the second positive-phase output terminal are connected via a second resistor. 3. A first positive-phase amplifying means and a second positive-phase amplifying means for non-inverting and amplifying an input signal, and a first negative-phase amplifying means and a first positive-phase amplifying means for inverting and amplifying the input signal. Two negative phase amplification means, a first positive phase output terminal connected to the output side of the first positive phase amplification means, and a second positive phase output terminal connected to the output side of the second positive phase amplification means. A positive phase output terminal, a first negative phase output terminal connected to the output side of the first negative phase amplification means, and a second negative phase output terminal connected to the output side of the second negative phase amplification means.
A negative-phase output terminal, the first positive-phase amplification means and the first negative-phase amplification means input a first input signal, and the second positive-phase amplification means and the second The anti-phase amplifying means inputs a second input signal, the first anti-phase amplifying means and the first anti-phase output terminal are connected via a first resistor, and the second anti-phase amplifying means is connected. An amplifier characterized in that the means and the second negative-phase output terminal are connected via a second resistance means. 4. The amplifier according to claim 2, wherein the first input signal and the second input signal are binary quantized signals. 5. The amplifier according to claim 2, wherein the first resistor and the second resistor are variable resistors. 6. The resistor according to claim 2, wherein each of the first resistor and the second resistor is a resistor unit including a plurality of resistors and a switching unit that switches a connection state of the plurality of resistors. Amplifier.