JPH0832360A - Linearity improving amplifier - Google Patents

Abstract

PURPOSE:To provide linearity upto the high range of a frequency area by performing constitution by a main amplifier circuit and a negative feedback circuit whose input/output characteristics are the same and first and second attenuators serially connected to the input side and the output side of a negative feedback amplifier circuit. CONSTITUTION:When it is assumed that the input of 2V0 is supplied to an input terminal and AV0 is outputted to the output terminal of the main amplifier circuit 30, when a straight line provided with the gradient of A/2 as the input/ output characteristics is attained, the linearity is improved. Attenuation to 1/A is performed in the first attenuator 32 and the input terminal of the negative feedback amplifier circuit 31 becomes AV0(X)--1/A=V0 The output terminal of the negative feedback amplifier circuit 31 becomes AV0+deltaV0, it becomes 1/A in the second attenuator 33 and (AV0+deltaV0)X1/A=V0+deltaV0/A is outputted to the output terminal. [2V0-{V0+delta(V0)/A}=V0-delta (V0) /A is outputted to the output terminal of a subtractor 34 and when it is assumed that V1=V0-deltaV0/A, V1 V0 is attained. 2V0 is inputted to the input terminal, AV0 is obtained in the output terminal and the linearity is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a linearity improving amplifier mainly used for AV equipment amplifiers and the like.

[0002]

2. Description of the Related Art Conventionally, an amplifier used in an AV machine or the like is required to faithfully supply an input waveform to the load of the amplifier. In particular, in the audio amplifier, since the speaker of the load has an inductance component, the current feedback amplifier circuit AMP as shown in FIG. 8 has been used in order to flow a current faithful to the input waveform of the amplifier to the speaker. Since the current feedback amplifier circuit AMP detects the current waveform flowing through the inductance L by the small resistance r and performs feedback, a current faithful to the input waveform flows through the inductance L. The fidelity increases as the return amount increases.

Further, generally, the counter electromotive voltage v is generated by the inductance L of the speaker, which is a cause of hindering the reproduction of a faithful output waveform. This current feedback amplifier circuit has the counter electromotive voltage v in its feedback loop. Since the generation source of is included, there is an advantage that the counter electromotive voltage v is canceled by the negative feedback action. The effect also increases as the return amount increases.

Negative feedback has been generally used for improving the input / output linearity of an amplifier, improving the waveform distortion, stabilizing the operating point, and the like. However, in order to achieve the linearity, the waveform distortion, and the stabilization of the operating point, it is necessary to apply sufficient negative feedback to the operating frequency and the required gain unless the amplifier has a bare characteristic of a considerably wide band and high gain. And the amplifier was expensive and impractical.

FIG. 9 shows the relationship between the frequency f and the gain G of the conventional amplifier. As shown in FIG. 9, the characteristics described above can be improved in the low frequency region where the feedback amount is large, but in the high frequency region where the feedback amount gradually decreases, the input / output linearity and the effect of improving the waveform distortion also gradually decrease. Go. Of course, if the naked characteristics of the amplifier are not sufficient in band and gain, improvement of the above-mentioned characteristics cannot be expected in any frequency band.

[0006]

In the above-mentioned conventional structure mainly composed of negative feedback, the cost of the amplifier becomes high in the circuit structure which focuses on the characteristic improvement, and the characteristic is not sufficiently obtained in the structure of the inexpensive amplifier. Had challenges.

The present invention is to solve the above-mentioned conventional problems, and to provide a linearity improving amplifier which is an inexpensive amplifier and has the best input / output linearity over the entire range from the low frequency region to the high frequency region. With the goal.

[0008]

In order to solve the above conventional problems, a linearity improving amplifier according to the present invention has a main amplification circuit and a negative feedback amplification circuit having the same input / output characteristics, and an input of the negative feedback amplification circuit. And a negative feedback circuit composed of a second attenuator connected in series to the output side, the negative feedback circuit being connected from the output side to the input side of the main amplification circuit. .

[0009]

With this configuration, the non-linear portion that deviates from the input / output linearity of the main amplifier circuit is corrected by the negative feedback amplifier circuit having the same characteristics as this main amplifier, which is different from the method of improving the characteristics by a large amount of negative feedback. The specifications required for the naked characteristics of an amplifier are extremely loose, and an inexpensive amplifier can provide input / output linearity even in a high frequency region.

[0010]

【Example】

(Embodiment 1) A linearity improving amplifier according to an embodiment of the present invention will be described below with reference to the drawings.

Prior to the description of the first embodiment, the principle of the present invention will be described with reference to FIG.

FIG. 1A shows the main amplifier circuit, FIG. 1B shows the input / output characteristic V (v) of the main amplifier circuit and the ideal input / output linearity characteristic R (v), and FIG. 1C shows the main amplifier circuit. It is a block diagram explaining the principle of a transfer function.

In FIG. 1A, reference numeral 30 is a main amplifier circuit, and the input / output characteristic V (v) of the main amplifier circuit 30 shown in FIG. 1B is expressed by the following equation.

“V (v) = Av + δ (v)” (Equation 1) where “A = V ₀ / v ₀ ” denotes an ideal gradient of the input / output linearity characteristic R (v), δ (v) represents the function of the non-linear portion.

Further, when the transfer function of the main amplifier circuit is obtained from (Equation 1), it is expressed by "V / v = A + δ (v)" (Equation 2). The transfer function is shown in FIG. 1 (c). It is shown like.

The present invention relates to a configuration for making the value of δ (v) in (Equation 1) and (Equation 2) as close as possible to 0, and the configuration is shown in FIG.

The construction principle will be described with reference to FIG. 2 which is a block diagram of the linearity improving amplifier according to the first embodiment of the present invention.

In FIG. 2, 30 and 31 have amplifier circuit characteristics having the same input / output characteristics and a transfer function of "A + δ".
(V) ”is a main amplification circuit and a negative feedback amplification circuit. Three
Reference numeral 5 denotes a negative feedback circuit, which is connected in series to the negative feedback amplifier circuit 31 and the input and output sides of the negative feedback amplifier circuit 31 and has first and second attenuators having transfer functions of attenuation amounts of "1 / A", respectively. It is composed of and. 34 is a subtractor for subtracting the output of the output end (e) of the second attenuator 33 from the input end (a), (f) is the output end of the subtractor 34, and (b) is the output end of the main amplification circuit 30. , (C) and (D) are negative feedback amplifier circuits 3
1 is an input terminal and an output terminal, respectively.

Embodiment 1 of the present invention constructed as described above
The operation of the linearity improving amplifier in 1) will be described below.

Here, when Av ₀ is output to the output terminal (b) of the main amplifier circuit 30 when the input of 2v ₀ is supplied to the input terminal (a), the linearity improving amplifier circuit in the present embodiment. The total input / output characteristic is a straight line with a slope of "A / 2" (that is, the required gain of the linearity improving amplifier total = A
If it becomes / 2), it is assumed that an optimum linearity improving amplifier is obtained.

First, when "Av ₀ " is output to the output terminal (b), it is attenuated to "1 / A" by the first attenuator 32, and the input terminal (c) of the negative feedback amplifier circuit 31 is "Av 0". ₀ x 1 / A =
v ₀ ”.

Next, when "v ₀ " enters the input of the negative feedback amplifier circuit 31, "Av ₀ + δ" appears at its output end (d).
(V ₀ ) ”is output, this output is attenuated to“ 1 / A ”by the second attenuator 33, and“ {Av
₀ + δ (v ₀ )} × 1 / A = v ₀ + δ (v ₀ ) / A ”is output.

On the other hand, the subtractor 34 subtracts the input end (a) from the output end (e) of the second subtractor 33, so that the value shown in the following equation is output to the output end (f) of the subtractor 34. To be done.

“2v ₀ − {v ₀ + δ (v ₀ ) / A} = v ₀ −δ (v ₀ ) / A” (Equation 3) Here, (Equation 3) is changed to “v ₁ = v ₀ −δ (v ₀ ) / A ”(Equation 4), the voltage v ₁ at the output end (f) is supplied to the main amplification circuit 30, and the output shown in the following equation is output to the output end (b). To be done.

“Av ₁ + δ (v ₁ ) = Av ₀ + δ (v ₀ ) + δ (v ₁ )” (Equation 5) In general, the value of δ (v) is the amount of deviation from the straight line R (v). It is shown, which is a small value of several percent.

Further, since the total required gain of the linearity improving amplifier is about 10 times, when "A / 2 = 10", A = 20, and δ (of the second term on the right side of (Equation 4). v
The value of ₀ ) is reduced to 1/20 and becomes a negligible value as compared with “v ₀ ”.

Therefore, since (Equation 4) becomes "v ₁ ≈v ₀ ", it becomes "δ (v ₁ ≈δ (v ₀ )", and (Equation 5) is approximately represented by (Equation 6). (See FIG. 1 (b)).

“Av ₁ + δ (v ₁ ) = Av ₀ −δ (v ₀ ) + δ (v ₁ ) ≈A (v ₀ )” (Equation 6) “2v ₀ ” is input to the input end (a). Is supplied, the output of “Av ₀ ” appears at the output end (b) of the main amplification circuit 30,
The linearity improving effect is approximately “1 / A” as compared with the case where the negative feedback circuit 35 is not provided.

In FIG. 2, when "A = 1", the first and second attenuators 32 and 33 can be omitted, and the first and second attenuators are the negative feedback amplifier circuit 31. It is also possible to aggregate them into one on the input side or the output side, and it is obvious that the transfer function of the attenuator at that time is "1 / A ² ".

As is apparent from the above description, the “δ (v) function” of the non-linear portion of the main amplifier circuit 30 is almost canceled by the “δ (v) function” of the non-linear portion of the negative feedback amplifier circuit 31. The total transfer function of the linearity improving amplifier is almost “A / 2”, and the input / output characteristic has a slope of “A / 2”.
Is almost a straight line. That is, it can be said that the feedback amount of "1 / A" is fed back in order to perform the negative feedback of 1/2 of the gain A, that is, 6 db.

FIG. 3 is a block diagram of a linearity improving amplifier in which a buffer amplifying circuit having the same characteristic and a gain of 1 is connected in series to the main amplifying circuit which is a main part of FIG.

FIG. 3A shows an attenuator 36 having an attenuation amount of "1 / A" between the main amplifying circuit 30 which is the main part of FIG. 2 and its output terminal (B), and the main amplifying circuit 30. 3 has a configuration in which a buffer amplification circuit 39 configured by serially connecting an amplification circuit 37 having the same characteristics as the above is inserted, and FIG.
It has a configuration in which another stage of a buffer amplification circuit having the same configuration as the buffer amplification circuit which is the main part of (a) is added.

In FIG. 3A, (1) to (7) are numbers showing the output ends of the respective components of the block diagram, 36 is an attenuator, 37 is an amplifier circuit, 39 is a buffer amplifier circuit, and 35 'is negative. The feedback circuit 38 is a second attenuator. The same parts as those in FIG. 2 are designated by the same reference numerals, and the description thereof will be omitted.

When a 3v ₀ input is supplied to the input terminal (a), Av ₀ is supplied to the output terminal (7) of the buffer amplifier circuit 39.
Is output, the optimum linearity is improved if the input / output characteristics of the linearity improving amplifier become a straight line having a slope of “A / 3” (that is, the required gain of the linearity improving amplifier total = A / 3). This will be explained assuming that an improved linearity improving amplifier has been obtained.

Since the same explanation has already been made with reference to FIG. 2, the voltage at the output end of each constituent element of FIG. 3A will be explained here.

First, when “Av ₀ ” is output to (7), it is multiplied by “1 / A” in the attenuator 32, and (1) becomes “v ₀ ”, which is amplified by the negative feedback amplifier circuit 31 (2 ) Is “Av ₀
+ Δ (v ₀ ) ”and becomes“ 2 / A ”in the second attenuator 38.
Multiplied (3) becomes “2v ₀ + 2δ (v ₀ ) / A”, and subtracted by the subtractor 34 (4) becomes “3v ₀ − {2v ₀ + 2δ”.
(V ₀ ) / A} = v ₀ −2δ (v ₀ ) / A = v ₁ ”
Amplified by the main amplification circuit 30 (5) is “Av ₁ + δ (v ₁ )
_{= A {v 0 -2δ (v} 0) / A} + δ (v 1) = Av 0 -2
δ (v ₀ ) + δ (v ₁ ) ”, and the attenuator 36 calculates“ 1 / (v ₀ ) + δ (v ₁ ) ”.
It is multiplied by "A" and (6) becomes "v ₀ -2δ (v ₀ ) / A + δ.
(V ₁ ) / A = v ₂ ”, which is amplified by the amplifier circuit 37 and (7) is“ Av ₂ + δ (v ₂ ) = Av ₀ −2δ (v ₀ ) + δ.
(V ₁ ) + δ (v ₂ ) ”.

In general, the value of δ (v) indicates the amount of deviation from the straight line R (v), which is a small value of several percent.

Further, since the total required gain of the linearity improving amplifier is about 10 times, if "A / 3 = 10", then A = 30 and "-2δ" in the second term of (4) above.
The value of −2δ (v ₀ ) of “(v ₀ ) / A” is reduced to 1/30 and becomes a negligible value as compared with v ₀ .

Therefore, since (4) is "v ₁ ≉v ₀ ", it is "δ (v ₁ ) ≅δ (v ₀ )".

When “v ₁ ≉ (v ₀ )” is satisfied, (6) becomes “v
₀ −δ (v ₀ ) / A = v ₂ ”, and similarly,“ −
Since −δ (v ₀ ) of “δ (v ₀ ) / A” is set to 1/30, “v ₀ ≈v ₂ ” and “δ (v ₀ ) ≈δ (v ₂ )”.

Therefore, the above equation (7) is expressed by the following equation. “Av ₀ −2δ (v ₀ ) + δ (v ₀ ) + δ (v ₀ ) ≈A
When a 3v ₀ input is supplied to the “v ₀ ” input end (a), an output of “Av ₀ ” appears at the output end (7) of the buffer amplifier circuit 39, and a linearity improving amplifier with improved linearity is obtained. can get.

This linearity improving effect is approximately "1 / A" as compared with the case where the negative feedback circuit 35 'is not provided.

3B can be described in the same manner as in FIGS. 2 and 3A, and the description thereof will be omitted. In this case, however, a linearity improving amplifier with improved linearity can be obtained.

The main amplifying circuit 30 and the buffer amplifying circuit 39, which are the main parts of FIGS. 3A and 3B, are constructed by the same transistor in an actual circuit, and each has an emitter grounded amplifying circuit (amplification factor). = A) and the emitter follower amplifier circuit (amplification factor = 1), it is easy to understand. Of course, the buffer amplifier circuit 39 may be a Darlington complementary circuit.

FIG. 4 is a circuit diagram of a block diagram of the linearity improving amplifier according to the first embodiment of the present invention shown in FIG.

The configuration of the linearity improving amplifier according to the first embodiment of the present invention will be described below with reference to FIG. FIG.
, 40 and 42 are input and output terminals of the main amplification circuit 41, 45 is a second attenuator connected in series to the output side of the negative feedback amplification circuit 44, SP is a speaker, and r _f is for current feedback detection. It is resistance.

The main amplifier circuit 41 includes at least one amplifier circuit OP1 and two complementary transistors Q1.
And Q2, and the gain is A times.
Similarly, the negative feedback amplifier circuit 44 also has at least one amplifier circuit OP2 and two complementary transistors Q2.
3 and Q4, and its gain is A times. Now, assume that when a voltage of 2v ₀ is supplied to the input terminal 40, a voltage of Av ₀ is obtained at the output terminal 42.

As described in the explanation of the block diagram of FIG. 2, the output voltage Av ₀ at the output terminal 42 is “1/1” at the first attenuator.
Since the total gain of the negative feedback amplification circuit 44 from the first attenuator is 1, the output is multiplied by A ”and the output is multiplied by A in the amplification circuit OP2 in the negative feedback amplification circuit 44. The attenuator is not shown. However, in reality, a current is supplied to the speaker SP by the voltage Av ₀ of the output terminal 42, and this current also flows through the current feedback detection resistor r _f connected in series with the speaker SP, and a voltage proportional to the current is applied across the resistor SP. Cause to.

[0049] When the average output impedance of the speaker SP and Z ₀ (the value depending on the frequency is different), the voltage e _f appearing across said current feedback detection resistor r _f is _{"e f = Av 0 × r f} / (Z ₀ + r _f ) ”(Equation 7).

In general, the electric power generated in the current feedback detection resistor r _f is the reactive power with respect to the active power required to generate sound in the speaker SP, and in order to reduce this, the current feedback detection resistor r _{f is used.} It is said that the smaller is, the more preferable. However, when the current feedback detection resistance r _f is small, the current feedback detection voltage e _f is small and the gain of the negative feedback amplification circuit 44 must be increased accordingly.

Amplifier circuit OP of the negative feedback amplifier circuit 44 of FIG.
Since the gain of 2 must be the reciprocal of the impedance division ratio of (Equation 7), the negative feedback resistance R ^* is as in (Equation 8), and the gain thereof is the value shown in (Equation 9).

"(Z ₀ + r _f ) R / r _f " (Equation 8) "(Z ₀ + r _f ) / r _f " ... (Equation 9) Therefore, the output e ₀ of the negative feedback amplifier circuit 44 is ( The product of Equation 7) and Equation 9 is obtained, and “{Av ₀ × r _f / (Z ₀ + r _f )} ×
{(Z ₀ + r _f ) / r _f )} = Av ₀ ″, which is expressed as (Equation 10) when the function δ (v ₀ ) of the nonlinear portion of the negative feedback amplifier circuit 44 is considered.

“E ₀ = − {Av ₀ + δ (v ₀ )}” (Equation 10) When the above (Equation 10) is input to the second attenuator 45, its output becomes (Equation 11). As shown, it is multiplied by "1 / A".

“− {Av ₀ + δ (v ₀ )} × 1 / A = − {v ₀ + δ (v ₀ ) / A}” (Equation 11) The output shown in (Equation 11) is an input terminal. The value shown in (Equation 12) is resistance-added to the input voltage 2v ₀ supplied to 40 and is supplied to the + input of the amplifier OP1. Here, the output impedance of the second attenuator 45 is "r" and "(A-1) r".
It is assumed that the parallel impedance with and has a value sufficiently lower than the resistance R for addition.

“2v ₀ − {v ₀ + δ (v ₀ ) / A} = v ₀ −δ (v ₀ ) / A = v ₁ ” (Equation 12) (Equation 12) is a non-linear function δ When the voltage is input to the main amplifier circuit 41 in consideration of (v), the voltage amplified by A times appears at the output terminal 42 thereof, and becomes as shown in (Equation 13).

“Av ₁ + δ (v ₁ ) = Av ₀ −δ (v ₀ ) + δ (v ₁ ) ≈Av ₀ ” (Equation 13) (Equation 13) is the same as (Equation 6), and already As detailed.

As described above, the main amplifier circuit 41 and the negative feedback amplifier circuit 44 having the same input / output characteristics are used, and the negative feedback amplifier circuit 44 has an attenuation amount of "1 / A" at the output side. By connecting the negative feedback circuit 46 composed of the second attenuator 45 between the input and the output of the main amplification circuit 41, the function δ (v) of the non-linear portion of the main amplification circuit 41 is negatively fed back. Since the function δ (v) of the non-linear portion of the amplifier circuit 44 is almost canceled and the input / output linearity of the linearity improving amplifier is made a straight line having a slope of “A / 2”, the input / output characteristic with less distortion is obtained. Is obtained.

Further, in the conventional amplifier circuit to which a large amount of negative feedback is applied, the input / output characteristic of the amplifier circuit becomes linear in the low frequency region where the feedback amount is large, but the input / output characteristic of the amplifier is linear in the high frequency region where the feedback amount is small. do not become. However, the configuration of the present embodiment is a method of canceling the non-linear portion of the input / output characteristic and correcting it linearly, so that the input / output characteristic is linearly corrected in the range of gain above the required gain regardless of frequency. be able to.

Further, as shown in FIG. 4, the speaker SP
When the back electromotive voltage is p and the input of the input terminal 40 of the main amplifier circuit 41 is 0v for convenience, the voltage applied to the current feedback detection resistor r _f is as follows.

“R _f · p / (r _f + Z ₀ )” (Equation 14) When (Equation 14) is supplied to the input of the negative feedback amplifier circuit 44, its output e ₀ is represented by the following equation. .

“− {R _f · p / (r _f + Z ₀ )} × {(r _f + Z ₀ ) / r _f } = − p” (Equation 15) (Equation 15) is the second damping Supplied to the input of the container 45,
The output is multiplied by "1 / A" and "-p x 1 / A = -p /
A ". This voltage is supplied to the main amplifier circuit 41
Since it is doubled, "-p" appears at the output terminal 42 of the main amplification circuit 41 as shown in "(-p / A) * A = -p" (Equation 16). This voltage is just the back electromotive force p of the speaker SP.
The counter electromotive force canceling effect can be obtained without modifying the means for improving the input / output linearity.
This has the same effect as the conventional method in which a large amount of negative feedback is applied to improve the counter electromotive voltage.

(Second Embodiment) A second embodiment of the present invention will be described below with reference to the drawings.

In the second embodiment, the following two points are improved in addition to the configuration shown in the first embodiment.

(1) In the speaker network system, one side terminal of the bass, mid-range and treble speakers is common.

The current feedback detection resistor r _f of FIG. 4 according to the first embodiment cannot be applied to individually drive the above speaker network system by the current negative feedback amplifier and the voltage negative feedback amplifier, and therefore can be applied. Improved the new current feedback signal detection circuit.

(2) The current feedback detection signal and the ripple detection signal are supplied to the differential inputs of the negative feedback amplifier circuit so that the ripple voltage superimposed on the power supply does not flow to the speaker and the common mode is removed.

FIG. 5 is a circuit diagram of a linearity improving amplifier according to the second embodiment of the present invention. In FIG. 5, 50 and 52 are input and output terminals of the main amplifying circuit 51, and 53 is two identical transistors connected in series between the collectors and collectors of the complementary output stage transistors Q1 and Q2 included in the main amplifying circuit 51. Resistors 60 and 61 having a resistance value of 2R
, 54 is an output terminal of the current feedback signal detection circuit 53, 55 is a resistor 65 having two identical resistance values 2R between the supply points of both positive and negative voltage power supplies 63, 64. A ripple detection circuit formed by connecting 66 in series, 56 is an output terminal extracted from the midpoint of the ripple detection circuit 55, and 57 and 59 are connected in series to the input side and the output side of the negative feedback amplification circuit 58, respectively. First and second attenuators.

The configuration and the operation for detecting the current flowing through the speaker SP and performing the current negative feedback are shown in FIG.
Although it can be applied to a system in which a speaker and an amplifier are integrated, the speaker network system that includes a bass, mid-range, and treble speaker and a filter network has one terminal on one side that is common to all speakers. However, there was an inconvenience that cannot be applied.

Therefore, one end of the speaker SP is connected to the ground terminal and the other end is connected to the output terminal 52 of the main amplifier 51,
The current feedback signal detection circuit 53 is connected to the main amplification circuit 51 instead of the current feedback detection resistor r _f .

The operation will be described in detail below.
When the input signal “2v ₀ ” is supplied to the input terminal 50, the output terminal 52 of the main amplifier circuit 51 has the same phase “A /
The output voltage v ₀ multiplied by 2 ”is output, and the speaker SP
Current flows through. The positive part of the waveform of the output voltage Av ₀ is
The current of the transistor Q1 connected to the complementary of the output stage of the main amplifier circuit 51 is suppressed and the current of the transistor Q2 is increased. This increased current i _p flows through the current detection resistor r _i connected to the collector of Q2, and “i _p ×
a voltage drop of r _i ”. The negative portion of the waveform of the output voltage Av ₀ suppresses the current of the transistor Q2 and increases the current of the transistor Q1. This increased current i _N
Flows through the current detection resistor r _i connected to the collector of Q1 and causes a voltage drop of "i _N × r _i ".

The current feedback signal detection circuit 53 composed of two resistors 60 and 61 connected in series is the main amplification circuit 51.
Is connected to the collectors of the transistor Q1 and the transistor Q2 connected to the complementary output stage, and outputs the difference in voltage drop appearing in the respective current detection resistors r _i to the output terminal 54.

A point to be noted here is that a large amount of current flows through the transistor Q2 on the negative power supply side with respect to the positive portion of the waveform "Av ₀ ", so that the output terminal 54 of the current feedback signal detection circuit 53 is negative. The voltage is output. That is, a voltage having the opposite polarity to "Av ₀ " is detected.

The voltage V _F appearing at the output terminal 54 can be derived by the following equation. "I = -Av ₀ / Z _0" ...... (Equation 17) where "Z _0" is the average impedance of the speaker.

When this current i flows through the current detection resistor r _i , V _F is given by (Equation 18). _{"V F = i × r i =} -Av 0 · r i / Z 0 = -Av 0 / W " ... (Equation 18) Here, the voltage of the "W = Z ₀ / r _i" (Equation 18) It is supplied to the input of the first attenuator 57.

In the explanation of the principle, the first attenuator 57 is "1 /
It has been described that since the transfer function of “A” is included and the gain of the negative feedback amplifier circuit 58 is “A”, the series of gains is 1 time.

That is, when “2v ₀ ” is input to the input terminal 50, the output of the main amplification circuit 51 becomes “Av ₀ ”, and its value is unchanged from the first attenuator 57 to the negative feedback amplification circuit 5.
8 and the output of the negative feedback amplifier circuit 58 is eventually “Av
It is also explained that it becomes " ₀ ".

However, in reality, the current feedback signal detection circuit 5
The voltage detected in 3 is "A" as shown in (Equation 18).
The voltage is extremely small, which is "r _i / Z ₀ " times v ₀ ".

This is because if the current detection resistance r _i is large, the reactive power increases and the efficiency deteriorates, so that it is set to a value extremely smaller than Z ₀ .

This attenuation is amplified by the amplifier circuit OP2, and a series of gains is set to 1 to output "Av" to the output of the negative feedback amplifier circuit 58.
_Since it is configured to generate a voltage of " ₀ ", it differs from the value of the transfer function described in the principle diagram, but this does not impair the principle of the present invention.

The output impedance of the current feedback signal detection circuit 53 is R because 2R are in parallel. Therefore, a signal whose output impedance is R and whose voltage is V _F is obtained at the output terminal 54. When this signal is supplied to the first attenuator 57, the voltage of the following formula is obtained.

“V _F WR / (R + WR) = V _F W / (W + 1)” (Equation 19) When the voltage of (Equation 19) is input to the negative feedback amplifier circuit 58, its output e ₀ is The value is given by (Equation 20).

[0082]

[Equation 1]

Substituting (Equation 18) into (Equation 20), "e ₀ = -Av ₀ W / W = -Av ₀ " (Equation 21) The output e ₀ of the negative feedback amplifier circuit 58 is -Av. It becomes ₀ .

The above "Av ₀ " is a value of gain only,
Considering the function of the non-linear portion, the negative feedback amplifier circuit 5
The output e ₀ of 8 is expressed by the following equation.

“E ₀ = − {Av ₀ + δ (v ₀ )}” (Equation 22) This equation is the same as (Equation 10) representing the output of the negative feedback amplifier circuit in FIG. This output is supplied to the second attenuator 59, and the following description is exactly the same as the description after (Equation 10) described with reference to FIG.
When 2) is input, the output of the attenuator 59 is multiplied by "1 / A" as shown in (Equation 23).

“− {V ₀ + δ (v ₀ ) / A}” (Equation 23) The output shown in (Equation 23) is resistance-added to the input voltage 2v ₀ supplied to the input terminal 50 (Equation 23). The value shown in 24) is supplied to the positive input of the amplifier OP1. Here, the impedance of the attenuator 59 is a parallel impedance of "r" and "(A-1) r", and has a value sufficiently lower than the resistance R for addition.

“2v ₀ − {v ₀ + δ (v ₀ ) / A} = v ₀ −δ (v ₀ ) / A = v ₁ ” ... (Equation 24) (Equation 24) When input to the main amplifier circuit 51 in consideration of (v), the voltage amplified by A times appears at the output terminal 52, and is as shown in (Equation 25).

“Av ₁ + δ (v ₁ ) = Av ₀ −δ (v ₀ ) + δ (v ₁ ) ≈Av ₀ ” (Equation 25) As described above, the main amplification circuit 51 and the negative feedback amplification are performed. The circuit 58 has the same input / output characteristics, and is composed of first and second attenuators 57 and 59 having an attenuation amount of "1 / A" on the input side and the output side of the negative feedback amplifier circuit 58, respectively. By connecting the feedback circuit between the input and the output of the main amplification circuit 51, the function δ (v) of the non-linear portion of the main amplification circuit 51 is converted into the function δ of the non-linear portion of the negative feedback amplification circuit 58.
(V) substantially cancels each other out, and the input / output linearity of the total linearity improving amplifier is made into a straight line having a slope of approximately "A / 2", so that an input / output characteristic with less distortion can be obtained. Further, the configuration of the current feedback signal detection circuit 53 has made it possible to apply to a speaker network system for bass, midrange and treble in which one side terminal of the speaker is connected to a common terminal.

The second improvement will be described below with reference to FIG. A ripple voltage is generally superimposed on both the positive and negative voltage power supplies 63 and 64.

When this ripple voltage is superposed on the current feedback signal detection circuit 53, the current detection resistance r _i has a small resistance value in order to reduce the reactive power as described above, and thus a minute current detection signal. However, the negative feedback amplifier circuit 58 requires a large amount of amplification. However, since the ripple voltage is greatly amplified by this, it is necessary to first remove the ripple voltage and then amplify only the current detection signal.

The ripple detection circuit 55 realizes this.
Is. The ripple detection circuit 55 includes two resistors 65 and 6 having the same resistance value 2R between the positive and negative voltage power supplies.
6 are connected in series, and the output terminal 5
6 is out. Both the positive and negative power supplies 63 and 64 have the same voltage, and the output terminal 56 has an output in which the ripple voltage is superimposed on the 0 potential, and its output impedance is a parallel resistance of 2R, that is, R. is there.

As is clear from (Equation 20), the gain of the amplifier circuit OP2 is "W". Therefore, in order to make the output voltage of the ripple detection circuit 55 the same level as the output voltage of the current feedback signal detection circuit 53, a resistor "R / (W + 1)" is inserted between the output terminal 56 and the ground to reduce the ripple voltage to " 1 / W ”times, and then an amplifier circuit OP2 via a resistor R
Connected to the negative input of. On the other hand, the current feedback signal detection circuit 5
Since the output "V _F = -Av ₀ / W" of No. 3 is connected to the positive input of the amplifier circuit OP2, the ripple voltage and the ripple voltage superimposed on the current feedback signal are in-phase removed.

Although the positive and negative power supplies 63 and 64 have the same voltage in the second embodiment, they do not necessarily have to have the same potential, and the output of the ripple detection circuit 55 is the common terminal (ground) of both the power supplies. As long as the potential is sufficient, it is clear that the series resistance value may be designed so that the ratio of both voltages and the ratio of both resistors are equal.

(Third Embodiment) FIG. 6 shows a block diagram of a linearity improving amplifier according to a third embodiment of the present invention.

Prior to the description of FIG. 6, the main amplifier circuit 51, the negative feedback amplifier circuit 58, and the first and second attenuators 5 of FIG.
The total gain from the input terminal to the output terminal of the linearity improving amplifier composed of 7 and 59 is "A / 2" as described above.
And is a negative feedback of 6db. In this case, in order to cancel the function δ (v) of the non-linear portion of the main amplification circuit and at the same time cancel the counter electromotive voltage p of the speaker SP, 6 dB is required.
I have also explained that the current negative feedback of is just right.

FIG. 6 shows the main amplifier circuit 30 shown in FIG.
In the linearity improving amplifier configured by the buffer amplifying circuit 39 and the negative feedback circuit 35 ', the function δ (v) of the non-linear portion of the linearity improving amplifier circuit is canceled, but it has already been described. Since the counter electromotive voltage p cannot be canceled out only by the current feedback, the voltage feedback signal detection circuit 70 is added to optimally distribute the respective feedback amounts of the current feedback and the voltage feedback, and the counter electromotive force p is counteracted with the function δ (v). It shows an embodiment of a configuration that can cancel the voltage p at the same time.

The optimum distribution of each feedback amount will be described below while explaining the operation of FIG.

In FIG. 6, 30 is a main amplifier circuit, 39 is a buffer amplifier circuit, 54 is an output terminal of the current feedback signal detection circuit 53, 52 is an output terminal of the amplifier circuit 37, and 71 is an output of the voltage feedback signal detection circuit 70. An end, 56 is an output end of the ripple detection circuit 55, 38 is a second attenuator, and 34 is a subtractor. The same parts as those in FIG. 2 of the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

The total gain from the input terminal (a) to the output terminal 52 in FIG. 6 is "A / 3" as described above.
It is a negative feedback of 5db. Among the negative feedback, the current feedback and the voltage feedback are distributed by the current feedback 6 dB rather than the voltage feedback.
By setting the large number and total negative feedback to 9.5 dB, the δ (v) function and the speaker counter electromotive voltage p are canceled at the same time.

In FIG. 6, it has already been described that Av ₀ is output to the output end 52 when the input of 3v ₀ is supplied to the input end (a). Of the total return amount "2 / A",
When the current feedback amount is X and the voltage feedback amount is Y, the respective feedback amounts are obtained by solving the following simultaneous equations.

“X + Y = 2 / A” …… Total feedback amount …… (Equation 26) “X−Y = 1 / A” …… The difference in feedback amount is 6 db …… (Equation 27) “X = 3 / 2A , "Y = 1 / 2A" is the solution.

Since the attenuation amount (feedback amount) of the second attenuator 38 is “2 / A”, the feedback amount of the current feedback loop is “(3 / 2A) ÷ (2 / A) = (3/4 ) ”(Equation 28), the feedback amount of the voltage feedback loop is“ (1 / 2A) ÷ (2 / A) = (1/4) ”(Equation 29), and (Equation 28), (Equation 28), The circuit operation of FIG. 6 will be described using Expression 29).

First, as described above, the current feedback loop is applied to the output terminal 54 of the current feedback signal detection circuit 53 (Equation 18).
The V _F signal having the output impedance R indicated by is output, and the voltage divided by the resistance of the dividing resistance “3WR / (W + 4)” is supplied to the positive input of the negative feedback amplifier circuit. The voltage of the positive input is given by the following equation.

[0104]

[Equation 2]

When (Equation 30) is amplified, the output e _c of the output terminal (2) of the negative feedback amplifier circuit becomes

[0106]

(Equation 3)

Substituting V _F of (Equation 18) into (Equation 31),

[0108]

[Equation 4]

Thus, the feedback amount of (Equation 28) is obtained. Next, the voltage feedback loop detects the voltage "Av ₀ " appearing at both ends of the speaker SP by resistance division of the voltage feedback signal detection circuit 70, and the voltage shown in the following equation is output to the output terminal 71 thereof. .

[0110]

(Equation 5)

When the voltage of (Equation 33) enters the negative input of the negative feedback amplifier circuit and is amplified, its output e _v is

[0112]

(Equation 6)

Thus, the feedback amount of (Equation 29) is obtained. Since the output terminal (2) of the negative feedback amplifier circuit by both the current and voltage feedback loops is the sum of the voltages of (Expression 32) and (Expression 33)

[0114]

(Equation 7)

Is already equal to the voltage appearing at the output terminal (2) in FIG. 3A, and the following description is also equivalent to that described in FIG. However, although the function δ (v) in the non-linear portion is omitted in the description of FIG. 6, this does not impair the principle of the present application.

Next, cancellation of the counter electromotive voltage p will be described with reference to FIG.

The counter electromotive voltage p appears in series between the output terminal 52 of the amplifier circuit 37 and the speaker SP as shown in the figure.

When this voltage p passes through the current feedback loop, "-p / W" appears at the output terminal 54 of the current feedback signal detection circuit 53.
Is output. This voltage is Av ₀ shown by V _F.
Therefore, the output e _cp of the output terminal (2) of the negative feedback amplifier circuit is equivalent to (Expression 32), and Av ₀ and p are exchanged.

[0119]

(Equation 8)

On the other hand, when a negative current flows through the speaker due to the counter electromotive voltage p, a negative voltage is generated at both ends of the speaker, and the output terminal 71 of the voltage feedback signal detection circuit 70 has "-p
A voltage of "/ 2 W" is generated. When this voltage is amplified by the negative feedback amplifier circuit, the voltage e _vp generated at its output end (2)
Becomes a value in which “−p” is replaced instead of Av ₀ in (Expression 34).

[0121]

[Equation 9]

The output terminal (2) of the negative feedback amplifier circuit is the sum of the above (formula 36) and (formula 37).

[0123]

[Equation 10]

When this output is supplied to the third attenuator 38, its output end (3) becomes

[0125]

[Equation 11]

[0126] (Equation 39) is A in the main amplifier circuit 30
Since it is multiplied by 1 and is multiplied by 1 in the buffer amplifier circuit 39, eventually "-
p ”appears at the output 52 of the buffer amplifier circuit 39.

This voltage has the opposite polarity to the counter electromotive voltage p and has the same voltage p.
Therefore, they cancel each other out. As is clear from the above description, the third embodiment provides a highly effective configuration capable of canceling the function δ (v) of the non-linear portion as well as the counter electromotive voltage p.

Also, in the configuration of FIG. 3B, it is possible to set the circuit constants that can exert the same effect as described above, but the description thereof is omitted here.

(Embodiment 4) FIG. 7 shows a circuit diagram of a linearity improving amplifier according to a fourth embodiment of the present invention.

In the fourth embodiment, the following four points are improved with respect to the structures shown in the first to third embodiments.

(1) Compared to the first embodiment, one side of the speaker can be connected to the ground.

(2) Compared with the second embodiment, only one current feedback detection resistor is required. (3) Compared with the second and third embodiments, the power supply ripple circuit is unnecessary.

(4) Compared to the third embodiment, the current feedback and the voltage feedback can be used together with one current feedback signal detecting resistor.

The operation of the fourth embodiment will be described in detail below with reference to FIG. The configuration of FIG. 7 differs from the configuration of FIG. 4 in the following four points.

(1) The current feedback signal detecting resistor r _f connected between the speaker and the ground in FIG. 4 is inserted in series between the output terminal 42 of the main amplifier circuit and the speaker, and the other end of the speaker is grounded. And (2) r
_f and the connection point on the output terminal 42 side of the main amplification circuit are connected to the positive input of the amplification circuit OP2 of the negative feedback amplification circuit 44 via a resistor, and (3) the connection point on r _f and the speaker side is negatively fed back. Connecting to the negative input of the amplifier circuit OP2 of the amplifier circuit 44 via a resistor, and (4) connecting the output of the second attenuator 45 to the negative input of the amplifier of the main amplifier circuit 41 via a resistor R,
That is, the feedback resistor having the gain “A” is set.

The components of FIGS. 7 and 4 are almost the same, and only the arrangement and connection of the components are changed.
Since the numbers given to the constituent elements and the operation of each constituent element have already been described, they are omitted here. In FIG. 7, when a voltage of “2v ₀ ” is supplied to the input terminal 40,
It is assumed that the voltage of "Av ₀ " is obtained at the output terminal 42. As described in the explanation of the principle of FIG. 2, the output voltage “Av ₀ ” of the main amplifier circuit is multiplied by “1 / A” in the first attenuator, and its output is multiplied by A in the negative feedback circuit. The total gain of the output of the negative feedback amplifier circuit from one attenuator becomes 1.
The first attenuator 43 is not shown in FIG. This is because the design may be made so that the total gain from the output terminal 42 of the output amplifier circuit to the output of the negative feedback amplifier circuit 44 becomes one.

The voltage “Av ₀ ” appearing at the output terminal 42 supplies a current to the current feedback signal detecting resistor “r _f ” and the speaker “Z ₀ ”, and a voltage proportional to this current is generated at both ends thereof. . Wherein the "e _1" the voltage across the "r _f", when the voltage generated at both ends of the speaker and "e _2", the voltage of the output terminal 42 of the main amplifier circuit "Av _0" is represented by the following formula It

“Av ₀ = e ₁ + e ₂ ” ... (Equation 40) The voltage “e ₁ + e ₂ ” is supplied to the amplifier circuit O via the input resistance “R”.
The voltage “e ₂ ”, which is connected to the positive input of P2 and is generated at both ends of the speaker, is amplified by the amplifier circuit OP2 via the input resistance “R”.
Connected to the negative input of.

In the circuit configuration shown in FIG. 7, when the total feedback amount "6db" is fed back as the current feedback, the function "δ (v)" of the non-linear portion is canceled and linearity is maintained, and at the same time, It has already been described that the counter electromotive force "p" generated in the speaker is also canceled.

In order to feed back all the feedback amount of current feedback,
It is necessary to have a circuit configuration in which only "e ₁ " is fed back.

It is sufficient to subtract the input of "e ₁ + e ₂ " and the input of "e ₂ " and remove "e ₂ ". Input resistance To accomplish this insertion positive and to the negative input of the negative feedback amplifier circuit 44 are both the same "R", a feedback resistor dividing resistor "R _1", "R _2" also are both the same "R ^* ”Can be achieved.

When the output of the negative feedback amplifier circuit 44 is "e ₀ ", the relationship shown in the following equation is obtained.

[0143]

(Equation 12)

The voltage “e ₁ ” generated across the current feedback signal detecting resistor “r _f ” is changed to “R ^* /” by the amplifier circuit OP2.
R "times to obtain a non-inverted output. On the other hand, as already described with reference to FIG. 2, the output “Av ₀ ” of the main amplifier circuit is multiplied by “1 / A” by the first attenuator and then “A” by the negative feedback amplifier circuit.
Since it is multiplied, the total amplification factor becomes 1, and “Av ₀ ” appears in the output of the negative feedback amplification circuit 44. That is, (Formula 41) becomes as follows.

[0145]

(Equation 13)

When “R ^* ” is calculated from (Expression 42), “R ^* = (Av ₀ / e ₁ ) R” (Expression 43) When (Expression 40) is substituted into (Expression 43),

[0147]

[Equation 14]

Since “e ₁ ” and “e ₂ ” correspond to “ _rf ” and “Z ₀ ”, respectively, (Equation 44) becomes as follows.

[0149]

(Equation 15)

(Equation 45) has exactly the same value as the feedback resistance "R ^* " obtained in FIG. That indicates that the gain for outputting an "Av _0" is fed back only voltage "e _1" generated current feedback detection resistor "r _f", and the output of the negative feedback amplifier circuit 44 is the same ing. The output “Av ₀ ” of the negative feedback amplifier circuit 44 is multiplied by “1 / A” by the second attenuator 45, and “v ₀ ” is supplied to the negative input of the amplifier OP1 of the main amplifier circuit 41.

The subsequent description is the same as that of the operation described with reference to FIG. 4, and the same effects such as non-linearity cancellation and counter electromotive voltage cancellation are also the same. Also, in the second embodiment shown in FIG. 5, the non-linearity and the counter electromotive voltage are canceled by a new current feedback signal detection circuit. Furthermore, in the second and third embodiments, ripple removal is also performed by the ripple detection circuit. This is because the current feedback signal detection circuits of Embodiments 1 and 2 are
Since the detected current negative feedback signal is supplied only to either the negative or positive input of the negative feedback amplifier circuit, when ripples were superimposed on the detected minute signal, this could not be removed.

[0152] Ripple for detecting a current feedback signal from both ends, and each of the detection end being connected positive and to the negative input of the negative feedback amplifier circuit of the fourth embodiment, current feedback signal detecting resistor "r _f" The components have the effect of being in-phase removed. As described above, the fourth embodiment shows a configuration in which the first and second embodiments are further improved, and satisfies the above-mentioned improvement points (1), (2), and (3).

Next, in the third embodiment, FIG.
Based on this, the nonlinearity and counter-electromotive force cancellation have been described. In addition, in canceling the counter electromotive voltage, it has been described that the current feedback of the total feedback amount can be achieved by setting "6 db" more than the voltage feedback.

[0154] In the fourth embodiment, will be described in detail voltage and current feedback signal detecting circuit simultaneously achieving current feedback and the voltage feedback by the amplifier circuit OP2 and current feedback signal detecting resistor "r _f".

In the third embodiment, the feedback amounts of the current feedback and the voltage feedback are specified. That is, the input end (a) of FIG.
As described above, the total gain from the output terminal 52 to the output terminal 52 is “A / 3”, which is a negative feedback of 9.5 dB.
Among the negative feedback, the current feedback and the voltage feedback are distributed such that the current feedback is 6 db more than the voltage feedback and the total negative feedback is 9.5 db, that is, the current feedback is 7.75.
db and voltage feedback to 1.75db
(V) Function cancellation and speaker back electromotive force "p" cancellation are performed at the same time.

In FIG. 6, "3v ₀ " is added to the input end (a).
It has already been described that "Av ₀ " is output to the output terminal 52 when the input of the above is supplied. Now the total return amount is "2 / A"
Among these, if the current feedback amount is “X” and the voltage feedback amount is “Y”, each feedback amount is obtained by solving the following simultaneous equations.

“X + Y = 2 / A” …… Total feedback amount …… (Equation 26) “X−Y = 1 / A” …… The difference in feedback amount is 6 db …… (Equation 27) “X = 3 / 2A , "Y = 1 / 2A" is the solution.

Since the attenuation amount (feedback amount) of the second attenuator 38 is "2 / A", the feedback amount of the current feedback loop is (Equation 28) and "(3 / 2A) ÷ (2 / A ) = (3/4) ”(Equation 28) The feedback amount of the voltage feedback loop is (Equation 29).

“(1 / 2A) ÷ (2 / A) = (1/4)” (Equation 29) This can be expressed as follows. That is, what is obtained by multiplying “e ₁ ” corresponding to the current feedback by “α” is “3/4” times the output “Av ₀ ” of the negative feedback amplifier circuit, and “e ₂ ” corresponding to the voltage feedback is represented by “β”. It is shown that it is sufficient that the multiplied _value becomes “1/4” times the output “Av ₀ ” of the negative feedback amplifier circuit. Mathematicalization of the above results in (Equation 46) and (Equation 47). Further, when both equations are added, (Equation 48) is obtained.

[0160] "e ₁ α = 3Av _0/4" ... (Equation 46) "e ₂ β = Av _0/4" ... (Equation 47) _{"e 1 α + e 2 β =} Av 0 " ...... (Equation 48 In addition, rewriting (Expression 46) and (Expression 47) gives the following expression.

“Α = 3 Av ₀ / 4e ₁ = 3 (r _f + Z ₀ ) / 4r _f ” ... (Formula 49) “β = Av ₀ / 4e ₂ = (r _f + Z ₀ ) / 4Z ₀ ” ... (Equation 50) On the other hand, when the input / output relationship of the negative feedback amplifier circuit is calculated from the input resistance “R”, the division resistance “R ₂ ”, and the feedback resistance “R ₁ ” shown in FIG.

[However, the derivation process of (Equation 51) is general and therefore omitted.)

[0163]

[Equation 16]

Further, (Equation 51) can be rewritten as follows. “E ₀ = e ₁ α + e ₂ β” (Equation 52) Here, “α” and “β” are as follows.

[0165]

[Equation 17]

[0166]

(Equation 18)

From (Equation 53) and (Equation 54),
Solve simultaneous equations for "R ₁ " and "R ₂ ".

[However, the derivation of simultaneous equations is general and therefore omitted.] "R ₁ = R (α-β)" (Equation 55) "R ₂ = Rα / (1-β)" (Equation 56) Applying (Equation 49) and (Equation 50) to “α” and “β” in (Equation 55) and (Equation 56), “R ₁ ”,
Calculate "R ₂ ". [Delivery process omitted]

[0169]

[Formula 19]

[0170]

(Equation 20)

“R ₁ ” of (Equation 57) and (Equation 58),
By choosing “R ₂ ”, optimal distribution of current and voltage feedback that cancels non-linearities and back electromotive forces can be achieved.

Also in the configuration of FIG. 3B, the circuit constants capable of exhibiting the same effect as described above can be determined, but the description thereof is omitted here.

As is clear from the above description, in the voltage / current feedback signal detection circuit, by selecting the gain of the negative feedback amplification circuit according to the number of stages of constituent elements, the improvement point (4), that is, the current feedback and The advantage that the voltage feedback can be used together with one current feedback signal detection resistor is achieved.

[0174]

As described above, according to the present invention, the main amplifier circuit and the negative feedback amplifier circuit having the same input / output characteristics and the first and second serially connected input and output sides of the negative feedback amplifier circuit are provided. It consists of a negative feedback circuit composed of an attenuator, and by connecting the negative feedback circuit from the output side to the input side of the main amplification circuit, the linearity of input and output can be maintained up to a high frequency region and at the same time the speaker Degradation of sound quality can be prevented by canceling out the counter electromotive voltage and removing the ripple voltage by using the in-phase removal of the differential input of the negative feedback amplifier circuit.

Further, also in the configuration of the buffer amplifier circuit connected in multiple stages to the main amplifier circuit, the function δ (v) of the non-linear portion
To maintain the linearity of input and output, and at the same time, the counter electromotive force of the speaker is also offset to improve the sound quality.

Further, by utilizing the phenomenon that the sound pressure rises due to the impedance increase and the current feedback amount decrease at the low self-resonant frequency of the dynamic speaker, the difference from 6db is used by using the current feedback and the voltage feedback together. It is possible to provide an amplifier in which the reproduction band can be expanded by decreasing the frequency-to-sound pressure characteristic so as to be flat.

Further, in the present embodiment, the explanation has been made mainly for the audio amplifier, but the linearity improving amplifier of the present invention can also be used for improving the linearity of amplifiers of video equipment and communication equipment. It is an object of the present invention to provide an amplifier exhibiting excellent effects that can be applied to amplifiers in a wide variety of fields such as an amplifier circuit after video detection of video and the like and an amplifier used for an A / D converter of digital equipment.

[Brief description of drawings]

FIG. 1A is a block diagram of a main amplifier circuit that is an essential part of the present invention. FIG. 1B is a characteristic diagram showing input / output characteristics of a main amplifier circuit and a feedback amplifier circuit that are essential parts. Block diagram showing transfer functions of certain main amplifier circuit and feedback amplifier circuit

FIG. 2 is a block diagram of a linearity improving amplifier according to the first embodiment of the present invention.

FIG. 3A is a block diagram in which one stage of a buffer amplification circuit, which is the same main part, is added. FIG. 3B is a block diagram in which two stages of a buffer amplification circuit, which is the same main part, are added.

FIG. 4 is a specific circuit diagram of FIG.

FIG. 5 is a circuit diagram of a linearity improving amplifier according to a second embodiment of the present invention.

FIG. 6 is a block diagram of a linearity improving amplifier according to a third embodiment of the present invention.

FIG. 7 is a circuit diagram of a linearity improving amplifier according to a fourth embodiment of the present invention.

FIG. 8 is a configuration diagram of a negative feedback amplifier circuit in a conventional example.

FIG. 9 is a diagram showing a relationship between the same frequency characteristic and a feedback amount.

[Explanation of symbols]

 30 Main Amplifier Circuit 31 Negative Feedback Amplifier Circuit 32 First Attenuator 33 Second Attenuator 34 Subtractor

Claims (8)

[Claims] 1. A main amplifier circuit and a negative feedback amplifier circuit having the same input / output characteristics, and first and second attenuators serially connected to an input side and an output side of the negative feedback amplifier circuit, respectively. And a negative feedback circuit, wherein the negative feedback circuit is connected from the output side to the input side of the main amplification circuit. 2. The main amplifier circuit has at least two transistors in a complementary output stage, and detects a current smaller than a load between a collector of each of the transistors and a supply point of both positive and negative voltages. The linearity improvement according to claim 1, further comprising a current feedback signal detection circuit which connects a resistor and two resistors having the same resistance value are connected between collectors of the respective transistors, and which extracts a current feedback signal from a midpoint thereof. amplifier. 3. The linearity improvement amplifier according to claim 1, wherein the negative feedback circuit is connected between the output terminal of the current feedback signal detection circuit and the input side of the main amplification circuit. 4. Two points are provided between both positive and negative voltage power supply points.
Ripple detection circuit for connecting the resistors in series and detecting the ripple of the power supply from the midpoint thereof, and the current feedback signal detection circuit, and the output of the ripple detection circuit and the current feedback signal detection circuit The linearity improvement amplifier according to claim 1, wherein the amplifier is supplied to each of the differential inputs of the negative feedback amplifier circuit. 5. A buffer amplifier circuit connected to the main amplifier circuit in at least one stage, and two resistors for dividing the output of a multistage amplifier connected to the buffer amplifier circuit and the voltage between the ground terminals. A voltage feedback signal detection circuit for extracting a voltage feedback signal from the midpoint of the two resistors, one of which adds the output of the voltage feedback signal detection circuit and the output of the ripple detection circuit to obtain the difference between the negative feedback amplification circuits. 5. The linearity improving amplifier according to claim 4, wherein the amplifier is supplied to a dynamic input and the output of the current feedback signal detection circuit is supplied to the other. 6. A multi-stage configuration of the buffer amplifier circuit, wherein a feedback amount is a sum of a current feedback amount of the current feedback signal detection circuit and a voltage feedback amount of the voltage feedback signal detection circuit, which is a total gain of the linearity improving amplifier. The linearity improving amplifier according to claim 5, wherein the difference between the current feedback amount and the voltage feedback amount is 6 db. 7. A current feedback signal detecting resistor, which is smaller than the load, is connected in series between the output of the main amplifier circuit and the load of the linear amplifier, and the connection point on the main amplifier circuit side is connected to the negative line. A voltage for obtaining a feedback signal of voltage and current from the output of the negative feedback amplifier circuit by connecting the connection point on the load side to the positive input of the feedback amplifier circuit via a resistor to the negative input of the negative feedback amplifier circuit. The linearity improving amplifier according to claim 1, further comprising a current feedback signal detection circuit. 8. The difference between the current feedback amount and the voltage feedback amount, wherein the sum of the current feedback amount and the voltage feedback amount of the voltage / current feedback signal detection circuit is the feedback amount that is the total gain of the linearity improving amplifier. The linearity improving amplifier according to claim 7, wherein is 6 dB.