JPH062816U - Vacuum tube power amplifier - Google Patents

Abstract

(57) [Abstract] [Purpose] In a power amplifier using a multi-pole vacuum tube or a positive excitation triode, the third harmonic caused by its shoulder characteristic while improving conversely without lowering the efficiency of operation. It suppresses distortion and greatly improves the distortion rate. In a single power amplifier or push-pull power amplifier using a multipole vacuum tube (1) as an amplifying element, a predetermined anti-cathode voltage is applied to a power supply line to one or two screen grids (3). It has a built-in current detector / generator (J) or impedance conversion amplifier that supplies a current with a low impedance while keeping it constant, and at the same time draws an equal current or a current proportional thereto from the plate output point with a high impedance. , Insert the distortion correction unit. In a power amplifier using a positive excitation triode, a similar unit is inserted in the excitation section of the control grid.

Description

[Detailed description of the device]

[0001]

[Industrial application range]

 The present invention relates to a vacuum tube power amplifier for linearly amplifying an audio signal or a high frequency signal.

[0002]

[Prior art]

 Today, most audio power amplifiers use a semiconductor as an amplifying element, but due to their good linearity as a single element, the one using a vacuum tube as an amplifying element is highly evaluated. There is a strong demand for vacuum tube audio power amplifiers. As a vacuum tube amplifying element, a pentode / beam tube is more efficient than a triode, and these polyodes are used when high output power is required.

In order to maintain the high efficiency of the pentode / beam tube, the screen grid is connected to a certain positive voltage power source by what is called a multi-pole connection, or the screen grid is wound at 40% of the output transformer. The so-called ultra-linear connection is used, which connects to taps of a line type.

Even in a triode, if a class A2 or class B2 power amplifier is constructed by using a class B dedicated tube or a positive drive tube that excites the control grid to a positive voltage region, high efficiency can be obtained, and therefore, it is suitable for an audio system. It may also be used in power amplifiers.

As a linear power amplifier for high frequency signals, a vacuum tube is used as an amplifying element, especially when low distortion is required or when a large amount of power is required, and in this case, a positive control grid is used. This method is used exclusively because high efficiency can be obtained by configuring a class AB2 or class B2 power amplifier using a class B dedicated tube that excites up to the voltage range.

In order to improve the distortion factor characteristic, a push-pull amplifier for reducing the second harmonic distortion is used for the single amplifier circuit. When lower distortion is required, a means to suppress the apparent distortion is provided by providing negative feedback only in the output stage or in the entire amplifier.

[0007]

[Problems to be solved by the present invention]

 Between the plate output voltage and the plate output current of the multi-electrode vacuum tube, when the plate voltage becomes low, a part of the cathode electron flow is shunted to the screen grid, so that the plate current sharply decreases in the low plate voltage region. There is a relationship to do. The plate voltage vs. plate current characteristic of this curved part is called the shoulder characteristic of the multi-pole tube. Due to this shoulder characteristic, a large amount of third harmonic distortion occurs at high output in the power amplifier using the multi-pole tube. There was a problem to do. If there is third harmonic distortion in the acoustic output of the speaker, it has the adverse effect of making the human ear uncomfortable, and unlike the second harmonic distortion, it can also be canceled by a push-pull amplifier circuit. Since it is a character that cannot be achieved, it was the greatest drawback of the multi-pole amplifier.

The ultra-linear connection reduces the third harmonic distortion to some extent, but is not perfect. It does not maintain the screen grid voltage constant and applies a signal voltage in a direction to suppress the plate output. Therefore, there was a problem that the amplification was lowered and the maximum output was also lowered to some extent. In addition, there is a problem in that it cannot be applied to all types of vacuum tubes because there is a limitation in use that the DC screen grid voltage is always the same as the plate voltage.

Therefore, in order to obtain a particularly low distortion, the so-called triode connection is used, in which the use of the multipole as the multipole is abandoned and the screen grid is combined with the plate to change the triode characteristics. However, there was a problem that output efficiency deteriorated naturally and it was impossible to construct a large output power amplifier.

A class A2 to class B2 power amplifier using a positive voltage excitation triode can obtain high output efficiency, but since a part of the cathode electron flow is shunted to the control grid, the plate voltage is reduced in the low plate voltage region. It has exactly the same drawbacks as the multipole amplifier in that the current decreases sharply and a large amount of third harmonic distortion occurs at high output.

Not only audio power amplifiers that are required to have high fidelity, but also high frequency power amplifiers cause radio wave interference due to spurious emission when harmonic distortion is generated. Therefore, it is necessary to eliminate this drawback.

Although a method of apparently reducing distortion by applying strong negative feedback to these high-efficiency amplifiers is also adopted, the negative feedback of strength easily impairs the stability of the entire amplifier and causes adverse effects such as deterioration of transient characteristics. It is the current situation that is regarded as a problem.

The present invention has been made in view of such circumstances, and it is possible to enhance the efficiency of a multipole power amplifier using a pentode / beam tube or a positive excitation vacuum tube power amplifier without lowering the efficiency. In addition, it completely suppresses the occurrence of third harmonic distortion due to shoulder characteristics. Since it does not improve the apparent distortion like negative feedback but improves the characteristics of the vacuum tube itself, there are no side effects such as deterioration of transient characteristics, and if desired, it can be used in combination with negative feedback. By doing so, it is possible to further improve the distortion rate.

Further, in the vacuum tube power amplifier, not only the third harmonic distortion caused by the shoulder characteristics of the multipole tube or the positive excitation triode, but also the third harmonic distortion caused by the basic structure of the vacuum tube. However, this was also the case for amplifiers using ordinary triodes. This distortion has a slight third-order nonlinearity for a single amplifier because the relationship between the grid input voltage of the vacuum tube and the plate output current follows the 3/2 square characteristic, and for the push-pull amplifier, it has a push-pull composite input. The relationship between voltage and output current is caused by the nonlinearity that the amplification factor is smaller in the large amplitude region than in the small amplitude region.

The 3/2 power characteristic of a vacuum tube is a characteristic that the total distortion factor during single operation is extremely small compared to other semiconductors, but especially the second harmonic distortion is canceled out. In the sprue amplifier, this causes a problem as a cause of generation of the third harmonic distortion, which has a relatively large distortion weight. The present invention exerts an effective suppressing effect on the third-order harmonic distortion peculiar to the vacuum tube power amplifier by slightly adjusting the component constants.

[0016]

[Means to solve the problem]

 The cause of the third harmonic distortion caused by the shoulder characteristic of the power amplification circuit of the multi-pole tube is that the plate current decreases by the amount of the current shunted to the screen grid with respect to the cathode current that originally did not include this distortion. Therefore, the screen grid current, or a current equal to the screen grid current, is merged into the plate output terminal so that the added current of the plate current and the screen grid current is output, and This also means that the constant voltage characteristic of the cathode of the screen grid is maintained, and at the same time, a load element that causes a characteristic change at the plate output terminal is not generated.

The general means for achieving this is as follows: (I) A multi-pole tube single power amplifier or a multi-pole push-pull power amplifier composed of a normal circuit (II) This is a current separation unit for distortion correction that has two terminals.

(I) a constant-voltage low-impedance current supply terminal that supplies a current to the screen grid while maintaining a predetermined counter-cathode voltage; and (ii) a constant-current high current that draws an equal amount of current from the plate output point. Impedance current sink terminal. The purpose is achieved by inserting this unit into the power supply line to the screen grid, one in the single power amplifier and two in the push-pull power amplifier.

Hereinafter, a more specific description will be given with reference to the conceptual diagram. One of the specific means for realizing the current separation unit for distortion correction as the above-mentioned general means is the impedance conversion unit according to claim 1 shown in FIG. 1, which has the following three terminals and has an impedance conversion amplifier. This is a current impedance conversion unit <unit A> that incorporates a.

<Terminal a> Reference voltage terminal that regulates the output DC voltage, <Terminal b> Low impedance current output terminal, and <Terminal c> High impedance current input terminal. <Terminal B> having an output voltage to the cathode determined by <Terminal B> is connected to the screen grid (3) of the multi-pole tube (1) to supply current at a constant voltage, and <Terminal C> is a plate. The screen grid current component (isg) connected to (2) and impedance-converted by the built-in impedance conversion amplifier (H) is added to the output with a constant current characteristic.

2, FIG. 3 and FIG. 4 show a current impedance conversion unit <unit A> composed of actual elements. 2 is a vacuum tube grid ground amplifier (7), FIG. 3 is a MOS-FET gate ground amplifier (8), and FIG. 4 is a bipolar transistor base ground amplifier (9). According to Fig. 2, in terms of direct current, it is a cathode follower amplifier that outputs the grid input reference voltage of <terminal a> with a gain of 1 and a low impedance to <terminal b>. It is a constant voltage power supply to the screen grid. is there. From an AC perspective, it is a grid ground amplifier that outputs the screen grid current signal input from the <terminal B> to the cathode with high impedance from <terminal C> to the plate end of the output tube. It is an impedance converter that keeps the same value and grounds <terminal a> to shield input <terminal b> and output <terminal c>. Therefore, the requirement as a current separation unit for distortion correction is satisfied.

The voltage shift circuit (I) is necessary because the operating DC voltage of the active element needs to be guaranteed even if the potential at the output point of the output tube plate connected to the <terminal C> fluctuates. In FIG. 2, a combination (n) of a choke transformer and a capacitor connected to a high voltage power supply (Eh) is used. Through the capacitor, the screen grid current is commutatively coupled to the plate output point. For the same purpose, in FIG. 3, a floating power source (LE) for potential shift is used. In FIG. 4, the high voltage power supply (Eh) and the PNP type inverting base grounding amplifier circuit (10) are used to shift the potential. It goes without saying that the above potential shifting method does not matter in combination with the used element (vacuum tube, MOS-FET, bipolar transistor).

FIG. 5 shows that the cascode circuit (11) is cascaded to further improve the constant voltage characteristic of <terminal B> and the constant current characteristic of <terminal C>. Although the MOS-FET is taken as an example, other elements can have the same configuration.

Another concrete means for realizing the current separation unit for distortion correction is the current extraction unit according to claim 2 shown in FIG. 6, which has the following three terminals and has a current detection / generator ( J) is a current extraction unit <unit B>. <Terminal D> Power supply terminal, <Terminal E> Low impedance current supply terminal, <Terminal F> High impedance current sink terminal. <Terminal D> is connected to a power supply (Esg) having a predetermined voltage with respect to the cathode and supplied with current, and <Terminal E> is connected to the screen grid (3) so that the current from the power supply is hardly disturbed. Current is supplied while maintaining constant voltage, and the built-in current detector / generator (J) detects this screen grid current value (isg) from between <Terminal D> and <Terminal E>, and the plate output end The same amount of current is drawn in with a high impedance from the <terminal> connected to, and as a result, the screen grid current is added to the plate output (2).

FIG. 7, FIG. 8 and FIG. 9 show a current extraction unit <unit B> composed of actual elements. The current extraction unit in Fig. 7 detects the current with the transformer (e) with a winding ratio of 1 connected to the <terminal E>, and the <terminal via the impedance converter composed of the grounded-gate amplifier circuit (13) F> draws in current.

8 and 9 show a current extraction unit using an electronic device, FIG. 8 is composed of bipolar transistors in all, and FIG. 9 is composed of MOS-FFT. In FIG. 8, a current equal to the screen grid current flowing out of <terminal E> is absorbed from <terminal F> through two stages of a so-called current mirror circuit. Although the resistance element (15) for current detection of the first stage current mirror circuit (K1) connected to the <terminal E> is selected to be a sufficiently small value so as not to impair the constant voltage property of the <terminal E>. It can be omitted if the balance of active elements is perfect. The second stage current mirror circuit (K2) inverts the polarity of the current at a low potential point such as the ground point.

FIG. 9 is a circuit diagram in which a P-channel current inverting gate grounded amplifier (L1) and an N channel current inverting gate grounded amplifier (L2) are cascaded to perform the same operation as in FIG.

Further, FIG. 10 shows the performance of the current mirror circuit, especially the constant current characteristic of the sink current, which is improved by the cascade connection current mirror circuit (M1, M2). In the figure, a composite circuit of a bipolar transistor and a MOS-FET is shown, but it is possible to construct it with only a bipolar transistor or only with a MOS-FFT.

In this circuit, the ratio of the resistance element (15) for current detection in the first stage is changed, and the ratio is reversed by the current balancing resistor (16) in the second stage. While maintaining the equality between the sink current and the screen grid current of the device, a device was added to reduce the heat loss of the device by reducing the first stage mirror current output. This engineer is also applicable to the configurations shown in FIGS. 7, 8 and 9.

The above-mentioned two types of means, <unit A> and <unit B>, are combined to form a stronger current separation unit <unit C> as shown in FIG. It is also possible. Do not connect the current input terminal <Terminal C> of <Unit A> directly to the plate, but connect it to the current supply terminal <Terminal E> of the succeeding <Unit B> to connect the current sink terminal <Terminal F> to the plate. By connecting to <terminal C>, the requirement for high impedance of <terminal C> can be relaxed, and at the same time, the requirement for low impedance of <terminal E> can be relaxed. In addition, the floating power supply that was required for <Unit A> is also unnecessary.

In FIG. 11, the <unit A> is composed of the MOS-FET shown in FIG. 3, and the <unit B> is composed of the bipolar transistor shown in FIG. Of course, other combinations are possible. The above is the means for eliminating the third harmonic distortion caused by the shoulder characteristics of the multipole tube.

Further, as compared with the third harmonic distortion, a relatively small amount of the third harmonic distortion is generated in the vacuum tube power amplifier due to the 3/2 square characteristic of the vacuum tube. . This distortion has a slight third-order nonlinearity for the single amplifier, and for the push-pull amplifier, the amplification factor in the large-amplitude region is larger than that in the small-amplitude region for the push-pull combined input voltage vs. It occurs because of the non-linearity of becoming slightly smaller.

On the other hand, the screen grid current of the multi-pole tube has a characteristic that it becomes extremely large in a large amplitude region. Therefore, if you add a small amount of current proportional to the screen grid current to the plate output current in addition to the current equal to the screen grid current required to completely cancel the distortion due to the shoulder characteristics, The 3rd harmonic distortion can be canceled well.

A single amplifier causes an increase in second harmonic distortion in exchange for a decrease in third harmonic distortion, but a push-pull amplifier in which the generation of second harmonic distortion is suppressed is The effect of drastically reducing the distortion rate can be obtained. Also for single amplifiers, the second harmonic distortion is said to cause less discomfort to the human ear than the third harmonic distortion. Therefore, by appropriately adjusting the screen grid current mixing ratio. The characteristics of the audio amplifier can be improved.

One means for realizing this within the scope of claim 1 is an extended current impedance conversion unit <unit D> as follows. The extended current impedance conversion unit <Unit D> has three terminals that have the same role as <Unit A> and an impedance converter built in. However, <Terminal C> is not the plate output end of the amplifier but the plate. It is connected to the increasing winding tap of the output transformer connected as a load to.

FIG. 12 shows a concrete configuration of the extended current impedance conversion unit <unit D>, which is composed of MOS-FETs as in FIG. There is no difference from the configuration of <Unit A>, and <Terminal C> is connected to an appropriate increasing winding tap (32) of the output transformer (31) connected as a load to the plate to change the ratio of the added current. It is only greater than 1. With this expanded impedance converter, a current proportional to the screen grid current is added to the plate output current, and in addition to the 3rd harmonic distortion caused by the shoulder characteristics of the multipole tube, the 3/2 square characteristic of the vacuum tube is added. It is also possible to cancel out the third harmonic distortion caused by.

Similar to <Unit A>, <Unit D> can be configured by a vacuum tube or a bipolar transistor, the characteristics can be improved by cascode connection, and the potential can be shifted to secure the operating DC potential of the amplification element. It is obvious that the method shown in FIGS. 2 and 4 may be used instead of using the power source.

Means for realizing the third harmonic distortion cancellation due to the 3/2 square characteristic within the scope of claim 2 is, in the current extraction unit <unit B> of claim 2, proportional to the current detection / generator. The coefficient is greater than 1. This extended current extraction unit <unit E> has three terminals that have the same role as <unit B>, and has a built-in current detection / proportional current generator.

FIG. 13 shows the extended current extraction unit <unit E> which is specifically configured by a current mirror circuit of a bipolar transistor. There is no difference from the configuration of <Unit B> shown in FIG. 8, and the ratio of the mirror current of the second stage current mirror circuit (K3) is set to 1 or more by changing the size ratio of the current balance resistor (16). It is a large one. The practical optimum ratio is in the range of 1-2. With this expanded current detection / proportional current generator, a current proportional to the screen grid current is added to the plate output current, and in addition to the 3rd harmonic distortion caused by the shoulder characteristics of the multipole tube, It is also possible to cancel the third-order harmonic distortion due to the 3/2 power characteristic.

It is obvious that <Unit E> can be configured by MOS-FFT as well as <Unit B>, characteristics can be improved by cascode connection, and performance can be enhanced by combining with <Unit A>. Is.

Similarly, the magnitude ratio of the current detection resistors of the first stage can be made different to reduce the mirror output current and reduce the heat loss of the element.

Further, also in the method shown in FIG. 7, that is, in the means for realizing <Unit B> using the transformer, the primary / secondary winding ratio of the transformer for current detection (e) is set to 1. It is also obvious that <Unit E> can be realized by changing the range to 2 or 2.

The action of canceling the third harmonic distortion using the above means is not limited to the pentode / beam tube multipole connection amplifier, but can be applied to the ultralinear connection amplifier as it is. In the conventional ultra linear connection circuit, the screen grid power is supplied from about 40% of the taps of the output transformer winding. Therefore, the screen grid current is not sufficiently combined with the output. Therefore, even if the distortion is suppressed by the negative return to the screen grid electrode, the distortion itself due to the shunting of the cathode current to the screen grid occurs as in the case of the multi-pole tube connection.

On the other hand, in the means of <unit A> and <unit C>, the current impedance conversion unit capable of cross-current input according to claim 3 is expanded, and a plate is applied to the DC potential of the reference voltage terminal <terminal a>. By dividing and adding about 40% of the output AC voltage, it is possible to construct an amplifier that operates equivalently to an ultra-linear connection amplifier and at the same time suppresses the third harmonic distortion.

FIG. 14 shows <Unit F> which is an extension of <Unit A> according to FIG. 3 so that AC input is possible. <Terminal> is an AC input terminal, and by adding a voltage of about 40% of the plate output AC voltage to this terminal, ultra linear connection operation becomes possible. Compared with a normal ultra linear connection amplifier, there is an advantage that the division ratio of the output AC voltage can be easily changed.

It is also possible to apply an input voltage signal to the amplifier to the AC input terminal <terminal> of <unit F>. Alternatively, it is possible to add a part of the output voltage of the paired spheres in the push-pull amplifier. By these means, the characteristics of the amplifier can be changed appropriately.

As mentioned above, the direct means for merging a current equal to or proportional to the screen grid current into the plate output terminal has been listed. However, between the screen grid supply line and the grid input terminal of the multi-pole power amplifier. By combining the current / voltage feedback means, it is possible to obtain the same effect.

The general means for realizing this current / voltage feedback is the current return unit according to claim 4 shown in FIG. 15, which has the following two terminals, and is a current detection / voltage generator and a positive feedback circuit. This is a current feedback unit <unit G> that incorporates a. <Terminal H> Power terminal and <Terminal> Low impedance current supply terminal.

Power is supplied from the power supply terminal <terminal H> having a predetermined voltage to the cathode, and <Terminal> is connected to the screen grid (3), so that the constant voltage is maintained without substantially interrupting the current from the power supply. The current is supplied while keeping it, and the current detection / voltage generator (N) generates a voltage (vsg) with respect to the ground, which is proportional to the screen grid current (isg) supplied from the current detection / voltage generator (N), and outputs it to the output tube (1). By feeding back to the control grid input (23) or the preamplifier with a suitable positive feedback means (P), an operational effect equivalent to adding a current proportional to the screen grid current to the plate output can be obtained.

The principle of operation will be described below. Now, let Gm be the grid voltage / plate current transconductance of the output tube and Gm2 be the grid voltage / screen grid current transconductance. Here, if the current detection / voltage generator conversion ratio is set to 1 / Gm and positive feedback is performed to the control grid, the input voltage v becomes 1 + Gm2 / Gm times the original value. Since this is multiplied by the grid voltage / plate current transconductance (Gm) and appears on the plate, the plate current is added to the original value v · Gm by v · Gm2. This increase is the screen grid current itself. Therefore, it is possible to exert the effect of reducing the third harmonic distortion caused by the shoulder characteristics of the multipole tube.

Further, if the conversion ratio of the current detection / voltage generator is N / Gm (N is 1 or 2) and is positively fed back to the grid, the increase of the plate current becomes N times the screen grid current, The effect of canceling the third harmonic distortion caused by the 3/2 power characteristic of the vacuum tube can be exerted. Since the cathode voltage of the screen grid is maintained at a constant voltage, the efficiency of the multi-electrode tube will not be reduced. However, since the plate current is not actually increased, the effect of increasing the output cannot be obtained.

FIG. 16 shows one of means for specifically realizing the current detection / voltage generator and the positive feedback circuit in the current feedback unit <unit G>. This is because a low-impedance transformer (wa) with an appropriate winding ratio connected to the current supply terminal <terminal> detects the screen grid current and the reverse current appearing in the secondary winding connected to ground is detected. It is a circuit that applies pressure to the cathode (21) of the output tube and, as a result, adds a voltage relative to the screen grid current to the output tube grid input. The feedback ratio is determined by the transformer winding ratio and the secondary impedance (20). If this impedance is made small enough, the internal resistance of the screen grid electrode can be ignored.

Another means for specifically realizing the current detection / voltage generator and the positive feedback circuit is shown in FIG. This is because a current mirror circuit (K1) connected to a current supply terminal <terminal> by a bipolar transistor, a MOS-FFT or a combination thereof extracts a current equal to the screen grid current, and this mirror current is grounded. This is a circuit for adding the voltage generated in the resistor (22) connected to the above to the grid input of the output tube through the positive feedback means (P2) consisting of the feedback voltage adding resistance.

The feedback ratio is determined by the ratio of the current branch ratio of the current mirror circuit, the voltage generating resistance value, and the feedback voltage adding resistance P2 of the grid input section. In order to obtain an accurate feedback voltage ratio, it is necessary to devise an actual circuit such as arranging a cathode follower amplifier of a vacuum tube in front of the input section. It is known that the performance can be improved by cascading a cascode circuit in the current mirror circuit.

It is also known that an impedance conversion unit <unit B> can be placed before the current feedback unit <unit G> to improve the constant voltage property of the screen grid voltage. In the above example, the positive feedback is directly added to the input of the output tube, but it may be added to the pre-stage amplifier after adjusting the feedback ratio.

In a class A2 to class B2 power amplifier using a positive voltage excitation vacuum tube such as a class B amplification dedicated tube or a positive drive tube, a portion of the cathode electron flow is shunted to the control grid, so in the low plate voltage region. The problem that the plate current sharply decreases and a large amount of third harmonic distortion occurs at high output is exactly the same as the phenomenon caused by the screen grid current in a multipole power amplifier. Therefore, the third harmonic distortion can be eliminated by the same means as the distortion correcting means of the multipole power amplifier described above.

The distortion reducing means of the power amplifier using the positive voltage excited triode vacuum tube or the positive voltage excited multipole vacuum tube of claim 5 will be described with reference to FIGS. 18, 19, 20, and 21.

FIG. 18 shows a current impedance conversion unit (AA) having exactly the same configuration and function as the current impedance conversion unit <unit A> to <unit D> of claim 1 in which a positive voltage excitation triode vacuum tube is used. It is connected to the voltage exciter for the control grid (23) of the used class A2 single power amplifier, that is, the input transformer (26). However, the potential shift circuit I required for the <unit A> to secure the screen voltage is unnecessary.

While maintaining the bias voltage determined by the control grid bias reference voltage (24) connected to <terminal a>, the control grid current is supplied from <terminal b> with low impedance, and this current is output to the output tube. The distortion due to the control grid current is corrected by pulling it in from the <terminal H> connected to the plate with high impedance.

It is obvious that <Unit AA> may have various configuration examples similar to the implementation example of <Unit A>. It is also possible to connect <Terminal C> to the primary winding tap of the output transformer and follow <Unit D>, which adds a current proportional to the control grid current to the output.

FIG. 19 shows a current impedance conversion unit (F F) having exactly the same structure and function as the current impedance conversion unit <unit F> capable of inputting alternating current according to claim 3 in which a positive voltage excitation triode vacuum tube is used. It is directly connected to the control grid 23 of the class A2 single power amplifier using. In order to raise the output impedance of the <terminal C> for current absorption, it is configured with a multi-pole vacuum tube, but it operates in exactly the same way as <Unit AA>, and at the same time the signal voltage input from the <terminal>. To directly excite the output tube 25 from the <terminal B>.

FIG. 20 shows a current extraction unit (BB) having exactly the same configuration and function as the current extraction unit <unit B> to <unit E> of claim 2 in which a positive voltage excitation multipole vacuum tube is used for A2. This is connected to a voltage excitation unit for the control grid 23 of the class single power amplifier, that is, an excitation amplification tube (30) forming a cathode follower circuit.

A current from the control grid excitation power source (29) connected to the <terminal D> is supplied to the voltage excitation unit 30 from the <terminal E> with a low impedance and is equal to or equal to the control grid current flowing there. A current proportional thereto is generated through a current detection / generator composed of two-stage current mirror circuits K1 and K2. This is pulled in from the <terminal> connected to the output tube plate with high impedance to correct the distortion caused by the control grid current.

<Unit BB> may have various configuration examples similar to the implementation example of <Unit B>.

FIG. 21 shows a current feedback unit (GG) having exactly the same configuration and function as the current feedback unit <unit G> of claim 4, which is a class A2 single power amplifier using a positive voltage excitation triode vacuum tube. It is connected to the voltage exciter, that is, the input transformer 26, to the control grid (23).

A current from the control grid excitation power supply 29 connected to the <terminal H> is supplied from the <terminal L> to the voltage excitation unit 26 with low impedance, and a voltage proportional to the control grid current flowing therethrough is supplied. It is generated by a current detection / voltage generator including a current mirror circuit K1 and a current / voltage conversion resistor 22. This is positively fed back through the positive feedback means (PP) that feeds back to the cathode of the pre-amplifier 30, and an effect equivalent to drawing a current proportional to the control grid current from the plate output point is obtained, and distortion caused by the control grid current is reduced. to correct.

Depending on the voltage value of the excitation power supply 29, the current mirror circuit may be omitted and the current detection / voltage generator may be composed of a single resistor.

Although the class A2 single power amplifier has been described above as an example, the control of two places is also possible for the class A2 or class B2 push-pull power amplifier using a positive voltage excited triode vacuum tube or a positive voltage excited multipole vacuum tube. Two units of the above distortion correction unit may be connected to the voltage excitation unit to the grid.

[0069]

[Action]

 As described above, the current impedance conversion unit <unit A> of claim 1, the current extraction unit <unit B> of claim 2 and the distortion correction means <unit C> which is a combination thereof are a multi-pole single or push-pull power amplifier. In contrast, the output voltage equal to the cathode current is loaded by maintaining the constant voltage characteristic of the screen grid against the cathode and adding the screen grid current component to the plate current without changing the impedance of the plate output point. Can be supplied to As a result, the power amplifier combined with these units eliminates the 3rd harmonic distortion caused by its shoulder characteristics without giving the effect of decreasing efficiency to the operation of the pentode / beam tube. At the same time, the output current is increased, resulting in a significant improvement in the distortion rate and, at the same time, an effect of improving the output efficiency.

Further, the extended current impedance conversion unit <unit D> of claim 1 and the extended current extraction unit <unit E> of claim 2 are for a multi-pole tube single push-pull power amplifier. In addition to the screen grid current, the proportional current is added to the plate current to overcome the non-linearity correction caused by the shoulder characteristics of the pentode / beam tube, and to combine the essential components of the vacuum tube amplifier. The non-linearity of the input voltage vs. output current characteristics can be corrected by the contradictory characteristics of the screen grid current. As a result, the power amplifier combined with these units has the function of suppressing the third harmonic distortion caused by the non-linearity inherent in the vacuum tube amplifier.

Further, the current impedance conversion unit <unit F 2> capable of inputting alternating current according to claim 3 performs the function of <unit A> while inputting an alternating current signal from the output side or the input side to the screen grid. Can be given. In this way, the above-mentioned effect can be exerted on the amplification circuit other than the multi-pole tube connection amplifier such as the ultra linear connection.

Further, the current feedback unit <unit G> of claim 4 positively feeds back a voltage proportional to the screen grid current to the grid input of the output tube for the multi-pole single or push-pull power amplifier. Through, there is an operational effect equivalent to adding a current proportional to the screen grid current to the plate output. Thus, the power amplifier to be combined with this unit does not have the effect of lowering the efficiency of the multi-tube operation of the pentode / beam tube, and the third-order harmonic distortion due to its shoulder characteristics and the 3/2 harmonic distortion. It exerts the effect of eliminating the third-order harmonic distortion due to the riding characteristics.

The distortion correction unit according to claim 5, that is, the current impedance conversion unit <unit AA>, the AC impedance-capable current impedance conversion unit <unit FF>, the current extraction unit <unit BB>, the current feedback unit <unit GG. > Indicates that the bias voltage of the control grid is maintained and the excitation is realized for the class A2 or class B2 single power amplifier or push-pull power amplifier using a positive voltage excited triode vacuum tube or a positive voltage excited multipole vacuum tube. However, the control grid current or a current proportional thereto can be added to the plate current. As a result, the power amplifier combined with these units has the effect of eliminating the third harmonic distortion caused by the branching of the cathode current to the control grid and improving the output efficiency.

[0074]

【Example】

 Examples will be described with reference to the drawings. FIG. 22 shows an embodiment of claim 2 in which the multipole tube single amplifier is combined with the current extraction unit <unit B> whose concept is shown in FIG. The current detection / generation unit by the two-stage cascode connection current mirror circuit whose specific configuration is shown in FIG. 10 is realized by bipolar transistors. This unit can also serve as an extended current extraction unit <unit E> by making a part (R2) of the current balance resistance of the second stage current mirror circuit variable. The circuit constant is an appropriate value when a 5-pole vacuum tube called UZ-42 is used as the output tube. R3 is a thermal protection resistor that reduces the power burden on the first-stage current mirror circuit.

FIG. 23 shows a multi-pole push-pull amplifier, which is a current separation unit reinforced by a combination of the impedance conversion unit <unit A> and the current extraction unit <unit B> whose concept is shown in FIG. 2 shows a combination of two units of unit C>, that is, an embodiment of the combination of claim 1 and claim 2. <Unit C> is realized by a combination of the current impedance conversion unit by the MOS-FET shown in FIG. 3 and the current detection / generation unit whose performance is improved by the cascode connection current mirror circuit shown in FIG. ing. This unit can also play the role of the extended current extraction unit <unit E> by making part of the current balance resistor (R2) of the second stage current mirror circuit variable. The circuit constant is an appropriate value when the EL34 5-pole vacuum tube is used as the output tube.

The reference voltage power supply connected to the <terminal a> of the current impedance conversion unit is a simple one in which the B power supply for the output tube is divided by a resistor, but the output tube B power source is simply changed by changing the resistance division ratio. Since it can be adapted to the optimum screen grid voltage depending on the type, it has the advantage of higher versatility than a single <Unit B> circuit.

Further, if the capacitor that makes <terminal a> AC ground potential is omitted, it is possible to apply an AC signal here and input it to the screen grid. It is also easy to see that the operation is rich in expandability, for example, if about% is fed back here, the operation can be made equivalent to that of an ultra linear connection amplifier.

FIG. 24 shows an embodiment of claim 4 in which two units of the current feedback unit <unit G> whose concept is shown in FIG. 17 are combined with the multipole push-pull amplifier. Positive feedback is applied to the cathode of the pre-amplifier through a resistor voltage divider circuit (33) which constitutes positive feedback means.

By changing the voltage dividing ratio, it is possible to adjust the feedback voltage ratio and change the degree of correction of the non-linearity of the multi-electrode tube. The circuit constant is an appropriate value when a 5-pole vacuum tube of 6 F6 is used as the output tube.

FIG. 25 shows an embodiment of claim 5 in which the impedance conversion unit <unit AA> of FIG. 18 is combined with the class B2 high frequency power amplifier using the class B amplification dedicated triode 572B. The power amplifier tube uses the grounded grid method to improve the high frequency characteristics, and the impedance conversion unit (AA) consisting of a small triode 811 is connected to the control grid to add the grid current to the output. . Select an appropriate value for the circuit constant according to the amplification frequency.

[0081]

[Effect of device]

 The most important third harmonic distortion reducing effect of the present invention is shown below by actual numerical values of the above-mentioned embodiment. 26 and 27 show the second harmonic distortion coefficient and the third harmonic distortion coefficient when the single amplifier of FIG. It is compared with that when the polar tube is connected.

FIG. 26 shows the characteristics when the variable portion (R2) of the current balance resistance is set to zero and operated as a current extraction unit <unit B> that adds a current equal to the screen grid current to the plate output. is there. The reduction effect of the 3rd harmonic distortion can be confirmed especially for large output. Also, a slight increase in maximum output can be confirmed.

FIG. 27 shows a case where R2 is set to about 0.5 times R1 and operated as an extended current extraction unit <unit E> that adds a current about 1.5 times the screen grid current to the plate output. It is a characteristic. It can be seen that the third harmonic distortion disappeared almost completely, and instead the second harmonic distortion increased. Also, it can be confirmed that the maximum output is increased more than in the case of FIG.

FIG. 28 shows the second-order harmonic distortion rate and the third-order harmonic distortion rate when the push-pull amplifier of FIG. 23 is created using a vacuum tube named EL34 and operated in class A. , It is compared with that at the time of normal multi-pole connection. Again, the variable part (R2) of the current balance resistance is set to about 0.5 times R1 and it operates as an extended current extraction unit <Unit E> that adds 1.5 times the screen grid current to the plate output. It is a characteristic when it is made to. The 3rd harmonic distortion is drastically reduced, the 2nd harmonic distortion increase is also small, and it can be confirmed that the overall distortion rate is greatly reduced. You can also see an increase in maximum output.

As described above, by applying the same amount of current as the screen grid current to the plate output by the impedance conversion unit A of claim 1 and the current extraction unit B of claim 2, the pentode / beam It is confirmed that the multi-tube operation of the tube is improved without giving the effect of lowering the efficiency, and the effect of reducing the third harmonic distortion due to its shoulder characteristics is reduced.

A screen is used as in the embodiment by using the expanded impedance conversion unit D according to claim 1 and the current extraction unit E according to claim 2 in which the ratio of the generated current of the current detection / generation means J is larger than 1. Adding a current proportional to the grid current to the plate output not only eliminates the 3rd harmonic distortion caused by the shoulder characteristics of the pentode / beam tube, but also eliminates the combined input voltage pair that is essential for the vacuum tube amplifier. It is confirmed that the third harmonic distortion caused by the non-linearity of the output current characteristic can also be suppressed.

As a result, the push-pull power amplifier, which originally has a small second harmonic distortion, has the effect of making the total distortion extremely small. In addition, in the single amplifier, the content ratio of the second-order harmonic distortion and the third-order harmonic distortion can be adjusted, which has the effect of selecting a sound quality that is comfortable for the human ear.

Further, the impedance conversion unit capable of overlapping the AC input from the reference voltage input terminal according to claim 3 has an effect of being highly adaptable in a circuit such as being able to correspond to an ultra linear connection amplifier. .

A power amplifier having a current feedback unit for positively feeding back a voltage proportional to the screen grid current to the grid input of the output tube according to claim 4 is a distortion correction unit for drawing a current proportional to the screen grid current from the plate output point. In order to obtain the same operational effect as it has, the push-pull power amplifier also has the effect of minimizing the total distortion. Further, in the single amplifier, the content ratio of the second harmonic distortion and the third harmonic distortion can be adjusted.

Thus, while maintaining high efficiency, the power amplifier using the multi-pole vacuum tube, which has the drawback that the generation of the third harmonic distortion is large while the power efficiency is high, is improved, while the power for audio is improved. The amplifier can be of extremely high quality.

A power amplifier using a positive-excitation vacuum tube having a distortion correction unit according to claim 5 adds a current equal to or proportional to the control grid current to the plate output current to generate a cathode current to a control grid current. The effect of significantly reducing the third-order harmonic distortion due to the branching can be obtained.

The power amplifier using the positive excitation vacuum tube has high efficiency even if the triode is used. However, due to the drawback that the generation of the third harmonic distortion is large so far, the power amplifier for audio is used. However, the invention according to claim 5 makes it possible to provide a very high-quality audio power amplifier.

Further, also in the linear power amplification of a high frequency signal, it is possible to realize a high quality power amplifier while suppressing the occurrence of spurious interference while maintaining its high efficiency.

[Brief description of drawings]

FIG. 1 is a general configuration diagram of a multipole power amplifier in which a current impedance conversion unit is combined.

FIG. 2 is a current impedance conversion unit composed of a vacuum tube.

FIG. 3 is a current impedance conversion unit including a MOS-FET.

FIG. 4 is a current impedance conversion unit including a bipolar transistor.

FIG. 5 is a current impedance conversion unit including a MOS-FET cascode connection amplifier.

FIG. 6 is a general configuration diagram of a multi-pole power amplifier in which a current extraction unit including a current detection / generator is combined.

FIG. 7 is a current extraction unit composed of a transformer.

FIG. 8 is a current extraction unit composed of a two-stage current mirror circuit of bipolar transistors.

FIG. 9 is a current extraction unit composed of a MOS-FFT two-stage grounded-gate current inverting amplifier.

FIG. 10 is a current extraction unit composed of a two-stage current mirror circuit consisting of a cascade connection of a bipolar transistor and a MOS-FET.

FIG. 11 is a current separation unit reinforced by combining a current impedance conversion unit and a current extraction unit.

FIG. 12 is a multi-pole power amplifier using an extended current impedance conversion unit with an increased degree of correction.

FIG. 13 is an expanded current extraction unit with an increased degree of correction.

FIG. 14 is a current impedance conversion unit capable of AC input.

FIG. 15 is a general configuration diagram of a multipole power amplifier combined with a current feedback unit.

FIG. 16 is a current feedback unit using a transformer.

FIG. 17 is a current feedback unit using a current mirror circuit.

FIG. 18 is a positive excitation triode power amplifier using a current impedance conversion unit.

FIG. 19 is a positive excitation triode power amplifier using a current impedance conversion unit capable of inputting alternating current.

FIG. 20 shows a positive excitation multipole power amplifier using a current extraction unit.

FIG. 21 is a positive excitation triode power amplifier using a current feedback unit.

22. The embodiment according to claim 2, which is a combination of a multi-pole tube single amplifier and a current extraction unit composed of a current mirror circuit of bipolar transistors.

23. The embodiment of claims 1 and 2 in combination with a multi-pole push-pull amplifier and an enhanced current isolation unit.

FIG. 24 is an embodiment of claim 4, which is a combination of a multi-pole push-pull amplifier and a current feedback unit using a current mirror circuit.

FIG. 25 is an embodiment of claim 5 in which a positive excitation triode power amplifier and a current impedance conversion unit are combined.

FIG. 26 is the harmonic distortion factor of the single power amplifier of FIG. 22 with a current equal to the screen grid current applied to the plate output.

FIG. 27 shows the harmonic distortion factor of the single power amplifier of FIG. 22 with 1.5 times the screen grid current applied to the plate output.

28 shows the harmonic distortion factor of the push-pull power amplifier of FIG. 23 with 1.5 times the screen grid current applied to the plate output.

[Explanation of symbols]

A Impedance conversion unit A1 Example of impedance conversion unit A2 Example of impedance conversion unit A3 Example of impedance conversion unit A4 Example of impedance conversion unit AA Impedance conversion unit for control grid B Current extraction unit B1 Example of current extraction unit B2 Example of current extraction unit Example B3 Example of current extraction unit B4 Example of current extraction unit BB Current extraction unit for control grid C Enhanced current separation unit D Extended impedance conversion unit E Extended current extraction unit Ea Heater power supply Eb B power supply Eh High voltage power supply Ek Negative power supply Esg Screen power supply F Current impedance conversion unit capable of AC input FF Current impedance conversion unit capable of AC input for control grid G Current feedback unit G1 Current feedback unit example G2 Current feedback unit example GG Control grid current feedback unit H Impedance conversion amplifier I Potential shift circuit Ic1 Control grid current isg Screen grid current J Current detector / generator K1 Transistor current mirror Circuit K2 Anti-polarity transistor / current mirror circuit L1 FET Current inverting circuit with gate grounded amplifier L2 Anti-polarity FET gate current inverting circuit with grounded amplifier M1 Cascode current mirror circuit M2 Anti-polarity cascode current mirror circuit N Current detection / voltage generation Device N1 Example of current detection / voltage generator N2 Example of current detection / voltage generator P Positive feedback means P1 Example of positive feedback means P2 Example of positive feedback means a Reference voltage terminal b Current output terminal c Current Power terminal D Power supply terminal E Current supply terminal F Current absorption terminal T AC input terminal H Power supply terminal Re Current supply terminal Nuke and condenser Floating power supply Transformer Transformer 1 Multipole output tube 2 Output tube plate 3 Output tube screen Grid 4 Screen grid Reference voltage 5 Input 6 Output load 7 Vacuum tube grid ground amplifier 8 FET grounded ground amplifier 9 Bipolar transistor base grounded amplifier 10 Inverted base grounded amplifier 11 FET cascode circuit 12 Bias circuit 13 FET grounded amplifier 14 Bias circuit 15 Current detection Resistor 16 Current balance resistor 17 Coupling capacitor 18 Amplifier output terminal 19 DC input resistor 20 Secondary impedance resistor 21 Output tube cathode 22 Current / voltage conversion resistor 23 Output tube control Lid 24 Control grid bias reference voltage 25 Positive voltage excitation 3-pole output tube 26 Input transformer 27 Auxiliary screen power supply 28 Positive voltage excitation multipole output tube 29 Control grid excitation power supply 30 Control grid excitation amplification tube 31 Output transformer 32 Primary Increase winding tap 33 Resistance voltage divider circuit 34 Input tuning coil 35 Tank coil 36 Tuning variable capacitor 37 Loading variable capacitor 38 High frequency choke

Claims (5)

[Scope of utility model registration request] 1. A single power amplifier or push-pull power amplifier using a multipole vacuum tube (1) as an amplifying element, and distortion correction inserted in a power supply line to one or two screen grids (3). A unit, that is, a reference voltage terminal (a) that regulates the output DC voltage, and an output voltage to the cathode determined by the reference voltage terminal (a), which is connected to the screen grid (3) of the multi-pole tube and supplies a current at a constant voltage. The impedance current output terminal (b) is connected to the plate output point (2) or the additional winding tap (32) of the output transformer (31) loaded on the plate, and the impedance-converted screen grid current component is absorbed. An impedance conversion amplifier (H, 7, which has three terminals of a high impedance current input terminal (c)) and executes the above impedance conversion. , Current impedance conversion unit with a built-in 9) (A, A1, A2, A
3, A4, D), while supplying a current to the screen grid at a low impedance while maintaining a predetermined voltage to the cathode, by drawing a current equal to or proportional to the current from the plate with a high impedance, Vacuum tube power amplifier with reduced distortion. 2. A single power amplifier or push-pull power amplifier using a multipole vacuum tube (1) as an amplifying element, and distortion correction inserted in a power supply line to one or two screen grids (3). A unit, that is, a power supply terminal (d) having a predetermined voltage to the cathode, and a low impedance current supply that is connected to the screen grid (3) and supplies a current while maintaining a constant voltage with almost no interruption of the current from the power supply. It has three terminals, a terminal (e) and a current absorption terminal (f) which is connected to the plate output point (2) and absorbs a current equal to or proportional to the screen grid current with high impedance. A current extraction unit (B, B1, B2, which incorporates a current detection / generator (J) that maintains proportionality with the current
B3, B4, E), while supplying a current with a low impedance to the screen grid while maintaining a predetermined voltage to the cathode, by drawing a current equal to or proportional to this with a high impedance from the plate, Vacuum tube power amplifier with reduced distortion. 3. The power amplifier according to claim 1, wherein a current impedance conversion unit (F) capable of inputting an alternating current signal to a direct current potential of a reference voltage terminal is overlapped. 4. A single power amplifier or push-pull power amplifier using a multipole vacuum tube (1) as an amplifying element, and distortion correction inserted in a power supply line to one or two screen grids (3). A unit, that is, a power supply terminal (h) having a predetermined voltage to the cathode and a low impedance current supply terminal (recessor) which is connected to the screen grid and supplies a current while maintaining a constant voltage characteristic with almost no interruption of the current from the power supply. ), And a current feedback unit (G, N, N1, N2) that includes a current detection / voltage generator (N, N1, N2) that generates a voltage to ground proportional to the screen grid current supplied from the terminal.
G1, G2) and means (P, P1, P2) for positively feeding back this voltage to the control grid input section of the output tube or the preamplification stage, whereby the voltage according to claim 1 or 2 is satisfied. ,
A vacuum tube power amplifier that has an operational effect equivalent to having a distortion correction unit that draws a current proportional to the screen grid current from the plate output point. 5. A class A2 to class B2 single power amplifier or a push-pull power amplifier using a positive voltage excited triode vacuum tube (25) or a positive voltage excited multipole vacuum tube (28), and one or two parts thereof. Control grid (2
3) has the same structure and function as the distortion correction unit inserted in the voltage excitation unit, that is, the current impedance conversion unit of claims 1 to 3, and the current output terminal B is directly connected to the control grid or its Voltage excitation unit (2
6, 30) or a current impedance conversion unit (AA, FF), which has exactly the same configuration and function as the current extraction unit according to claim 2, and the current supply terminal E is directly connected to the control grid or its voltage excitation. A current extraction unit (BB) connected to the section (26, 30) or having exactly the same configuration and function as the current feedback unit according to claim 4, wherein the current supply terminal is directly connected to the control grid or its voltage excitation section. A current feedback unit (GG) connected to (26, 30), which maintains the predetermined bias voltage and realizes the excitation of the control grid, while at the same time as or equal to the current flowing into the control grid. The current proportional to is actually drawn from the plate with high impedance, or the positive feedback means (PP)
Vacuum tube power amplifier with equivalent effect and reduced distortion.