JP6473258B2 - Vacuum tube for analog amplification - Google Patents

Description

  The present invention relates to an analog amplification vacuum tube that operates as an analog amplifier.

  As a technique related to a vacuum tube, a fluorescent display tube is known. For example, structures shown in Patent Documents 1 and 2 are known. In Patent Document 1, a linearly stretched filament that emits thermoelectrons at a predetermined temperature or higher is called a “heater H”. An anode ("Anode 4" in Patent Document 1) disposed in parallel with the filament and a grid disposed between the filament and the anode so as to face the anode are provided (first in Patent Document 1). Figure, see Figure 2). The basic structure of Patent Document 2 is the same as that of Patent Document 1. Further, as a method for controlling the fluorescent display tube shown in Patent Literatures 1 and 2, the driving method shown in Non-Patent Literature 1 is known.

Japanese Utility Model Publication No. 49-5240 JP 2007-42480 A

Noritake Ise Electronics Co., Ltd., “Fluorescence Display Tube (VFD) Application Note Driving Method-Driving Method”, [Search July 8, 2015], Internet <https://www.noritake-itron.jp/cs/ appnote / apf100_vfd / apf201_houshiki.html>.

  Since there is a demand from users who prefer the characteristics of vacuum tubes mainly in the music industry, there is a demand for vacuum tubes used as analog amplifiers, and there are vacuum tubes that can be used as analog amplifiers. However, there is a problem that the production amount is decreasing, and the price increases and acquisition is difficult. On the other hand, a fluorescent display tube, which is a kind of vacuum tube and is inexpensive and popular, is digitally controlled as can be seen from the driving method shown in Non-Patent Document 1, so that the on-off characteristics are stable. Good. However, in order to use it as an analog amplifier, stability of characteristics at a high level is required.

  An object of the present invention is to stabilize the characteristics of a vacuum tube having a structure close to a fluorescent display tube that is inexpensive and easily available (a vacuum tube in which an anode is formed on an insulating substrate).

  The vacuum tube for analog amplification of the present invention includes a filament, an anode, a grid, and an antistatic electrode. The filament is stretched in a straight line and emits thermoelectrons. The anode is formed on a substrate of an insulator arranged in parallel with the filament. The grid is disposed between the filament and the anode so as to face the anode. The antistatic electrode is formed on the substrate so as to be insulated from the anode. The antistatic electrode is connected to a ground or a positive direct current voltage source.

  According to the analog amplification vacuum tube of the present invention, it is possible to prevent changes in characteristics of the analog amplification vacuum tube due to the negative charge being charged around the anode by the antistatic electrode, so that the characteristics can be stabilized.

The top view of the vacuum tube for analog amplification. Sectional drawing when the vacuum tube for analog amplification of a prior application is cut by the AA line of FIG. The figure which shows the shape of a grid. The figure which shows a mode that the anode was formed on the glass substrate. The figure which shows the mode of an amplifier circuit. 0.3mm approximately the distance between the anode and the grid spacing of the filament and the grid showing the relationship between the anode voltage V _a and current I _p in the case of the order of 0.4mm for each voltage grid FIG. View showing the relationship between the anode voltage V _a and current I _p when the characteristics change for each voltage of the grid. Sectional drawing when the analog amplification vacuum tube of the 1st example of an antistatic electrode is cut by the AA line of FIG. The figure which shows a mode that the anode and antistatic electrode of the 1st example of the antistatic electrode were formed on the glass substrate. The figure which shows the mode of the amplifier circuit of the 1st example of an antistatic electrode. Sectional drawing when the analog amplification vacuum tube at the time of the 2nd, 3rd, 4th example of an antistatic electrode is cut by the AA line of FIG. The figure which shows a mode that the anode and antistatic electrode in the 2nd example of an antistatic electrode were formed on the glass substrate. The figure which shows the mode of the amplifier circuit at the time of the 2nd, 3rd, 4th example of an antistatic electrode. The figure which shows a mode that the anode and antistatic electrode in the 3rd example of an antistatic electrode were formed on the glass substrate. The figure which shows a mode that the anode and antistatic electrode in the case of the 4th example of an antistatic electrode were formed on the glass substrate. Sectional drawing when the vacuum tube for analog amplification at the time of the 5th example of an antistatic electrode is cut by the AA line of FIG. The figure which shows a mode that the anode and antistatic electrode in the case of the 5th example of an antistatic electrode were formed on the glass substrate. The figure which shows the mode of the amplifier circuit at the time of the 5th example of an antistatic electrode. The figure which shows the amplifier circuit at the time of connecting a direct-current voltage source to an antistatic electrode. The figure which shows the amplifier circuit at the time of using the bias power supply of a grid as a DC voltage source connected to an antistatic electrode.

  Hereinafter, embodiments of the present invention will be described in detail. In addition, the same number is attached | subjected to the structure part which has the same function, and duplication description is abbreviate | omitted.

<Description of invention of prior application>
Although not disclosed at the time of filing of the present application, the prior application (Japanese Patent Application No. 2015-8345) of the present applicant shows a vacuum tube for analog amplification that has a structure close to a fluorescent display tube that is inexpensive and easily available, and that is easy to operate as an analog amplifier. Has been. 1 is a plan view of an analog amplification vacuum tube, FIG. 2 is a cross-sectional view of the analog amplification vacuum tube of the prior application taken along the line AA in FIG. 1, FIG. 3 is a diagram showing the shape of a grid, and FIG. FIG. 5 is a diagram illustrating a state in which an anode is formed on a glass substrate, and FIG.

  The vacuum tube 900 for analog amplification shown in the prior application includes a filament 110 that is stretched in a straight line that emits thermoelectrons at a temperature higher than a predetermined temperature, an anode 120 that is arranged in parallel with the filament 110, and a filament 110 and an anode 120. The grid 130 is disposed so as to face the anode. The first feature is that the distance between the filament 110 and the grid 130 is not less than 0.2 mm and not more than 0.6 mm. Further, the second feature may be that the distance between the anode 120 and the grid 130 is 0.15 mm or more and 0.35 mm or less. As shown in FIG. 4, the anode 120 is formed on a flat substrate (glass substrate 125). 4 indicates the position of the frame portion 131 of the grid 130 (in other words, the portion facing the frame portion 131). An anode terminal 121 is connected to the anode 120 via an anode wiring 122. The anode 120 may be formed of, for example, an aluminum thin film. In FIG. 1, a part of the grid 130 is not shown so that the position of the anode 120 can be seen. In the actual analog amplification vacuum tube 900, the mesh 120 (see FIG. 3) is present on the anode 120, so that the anode 120 is difficult to see. The analog amplification vacuum tube 900 seals the case 180 and the glass substrate 125, and evacuates the air from the exhaust hole (not shown) to make the inside vacuum. An actual analog amplification vacuum tube is also provided with a getter ring or the like, but the description thereof is omitted because it is not related to the present invention.

  Filament 110 is a direct cathode. For example, the filament 110 may be coated with barium oxide so as to emit thermal electrons when heated to about 650 degrees by passing a direct current. In this example, the above “predetermined temperature” is 650 degrees, but is not limited to 650 degrees. The filament 110 is fixed to the filament support member 113 with a predetermined tension applied thereto. The tension is preferably determined so that the fundamental frequency of filament vibration is increased. If the fundamental frequency can be adjusted to 10 kHz or more, it is difficult for humans to hear noise caused by filament vibration.

  As shown in FIG. 3, the grid 130 includes a mesh portion 132 having a mesh shape and a frame portion 131 existing around the mesh portion 132. The grid 130 may be formed of SUS or the like. As described above, in FIG. 1, a part of the grid 130 is omitted for easy understanding of the anode 120. The actual grid 130 is as shown in FIG. The grid 130 is fixed to the grid support member 133. The distance between the anode 120 and the grid 130 and the distance between the filament 110 and the grid 130 are determined by the plate thickness of the grid support member 133.

The filament 110 is connected to a DC voltage source 310 (for example, 0.7 V), and is heated to a predetermined temperature (for example, 650 degrees) that emits thermoelectrons. The anode voltage _{V a} is applied via the resistor 325 by an anode voltage source 320 to the anode 120. Then, for example, a signal V _{g in} which a predetermined bias voltage V _gb is added to the input signal Vin is input to the grid 130. Then, the voltage _{Vout of the} anode 120 is output.

Next, the necessity of the features of the invention of the prior application will be described. A general fluorescent display tube is also arranged so that the filament stretched in a straight line that emits thermoelectrons at a temperature above a predetermined temperature, the anode arranged parallel to the filament, and the anode between the filament and the anode With a grid. However, in the case of a general fluorescent display tube, the distance between the anode and the grid is about 0.5 mm or more, and the distance between the filament and the grid is about 1.0 mm or more. Further, the fundamental frequency of the natural vibration of the filament is not considered. In the case of a fluorescent display tube, since ON / OFF control is performed, it is necessary to avoid current flowing halfway when the voltage of the grid is changed. Therefore, the dimensions are as described above. Further, when used as a fluorescent display tube, since an afterimage of a human is also used, it is not necessary to always apply an anode voltage, so that the anode voltage can be set high. On the other hand, since in order to use as an analog amplifier, it is necessary to constantly apply the anode voltage can not be increased consideration of the anode voltage V _a the effects of thermal expansion. In other words, the fact that the anode voltage cannot be increased is also a cause of difficulty in use as an analog amplifier as compared with use as a fluorescent display tube.

6, about 0.3mm spacing of the anode and the grid spacing of the filament and the grid showing the relationship between the anode voltage V _a and current I _p in the case of the order of 0.4mm for each voltage of the grid. From this figure, if the bias voltage V _gb 3V, the maximum value of the amplitude of the input signal V _in and 1V, it can be seen that the anode voltage V _a is obtained substantially linear amplification characteristics in a range of more than about 4V. Therefore, it is easy to use as a vacuum tube for analog amplification. And if the space | interval of the filament 110 and the grid 130 is 0.2 mm or more and 0.6 mm or less, it can be set as a vacuum tube which can be easily used for analog amplification compared with a general fluorescent display tube. That is, according to the (first) feature of the analog amplification vacuum tube of the prior application, the flow of electrons from the filament to the anode can be changed in an analog manner according to the potential of the grid, so that it is easy to use as an analog amplifier.

  When the distance between the anode 120 and the grid 130 exceeds 0.35 mm, the grid support member 133 needs to be bent. On the other hand, if the distance between the anode and the grid is 0.15 mm or more and 0.35 mm or less, the grid support member 133 can be configured by simply punching a flat plate. In this case, since the gap between the anode and the grid is determined only by the plate thickness of the grid support member, a highly accurate gap can be maintained. In addition, when the grid support member 133 is bent and formed, the grid also easily vibrates and causes noise. When the grid support member 133 is a flat plate punching process, the vibration of the grid can be suppressed, and the vacuum tube can be easily used for analog amplification.

<Analysis>
The analog amplification vacuum tube 900 of the prior application can obtain the characteristics shown in FIG. 6 when the use is started, but a phenomenon occurs in which the characteristics are not stable while continuing to be used. The relationship between the anode voltage V _a and current I _p when the characteristics change Figure 7 shows for each voltage of the grid. It can be seen that the anode current _Ia is difficult to flow as _a whole. For example, (see portion B in FIG. 6) in the characteristic shown in FIG. 6 the anode voltage V _a start flowing the anode current I _a from around 1V, 1V anode voltage V _a is a characteristic shown in FIG. 7 it is seen that flow anode current I _a is around (see part C of FIG. 7). It was also found that the analog amplification vacuum tube once having the characteristics shown in FIG. 7 returns to the characteristics shown in FIG. 6 when left unused for a long time.

From this phenomenon, causes a negative charge to the glass substrate 125 is charged by the use, the anode current I _a by the negative charges charged is considered to become difficult to flow. Referring to FIG. 5, since the negative charge is not charged on the glass substrate 125 before the use of the analog amplification vacuum tube 900, the electrons emitted from the filament 110 are attracted to the grid 130 and flow to the anode 120. . However, it is considered that some electrons are charged on the glass substrate 125 and the electrons prevent the flow of electrons from the filament 110 to the anode 120. Further, if the charged negative charge is constant, the characteristics are stable. However, since the charged charge cannot be controlled, the characteristics are considered to be unstable.

<Invention>
The analog amplification vacuum tube 100 of the present invention includes a filament 110, an anode 120, a grid 130, and an antistatic electrode 220. The filament 110 is stretched in a straight line and emits thermoelectrons. The anode 120 is formed on an insulating substrate (glass substrate 125) arranged in parallel with the filament 110. The grid 130 is disposed between the filament 110 and the anode 120 so as to face the anode 120. The grid 130 includes, for example, a mesh portion 132 and a frame portion 131 that exists around the mesh portion 132. The antistatic electrode is formed on the same plane as the anode 120 (on the glass substrate 125) so as to be insulated from the anode 120. When the grid 130 includes the mesh portion 132 and the frame portion 131, the antistatic electrode may be formed at least at a part of the portion facing the mesh portion 132. The antistatic electrode is connected to a ground or a positive direct current voltage source. The filament 110, the anode 120, and the grid 130 are the same as the analog amplification vacuum tube 900. The difference is that an antistatic electrode is provided. However, the grid 130 may be formed of only the mesh portion 132. That is, the part of the frame part 131 shown in FIG.

  There are several examples of the antistatic electrode as will be described later, but what is common is that the electrode is formed on the same substrate as the anode 120 so as to be insulated from the anode 120. The antistatic electrode around the anode 120 is important. In the case where the grid 130 includes the mesh portion 132 and the frame portion 131, the antistatic electrode may be formed at least at a part of the portion facing the mesh portion 132. The antistatic electrode is preferably connected to a ground or a positive potential DC power source. According to the analog amplification vacuum tube of the present invention, it is possible to prevent changes in characteristics of the analog amplification vacuum tube due to the negative charge being charged around the anode by the antistatic electrode, so that the characteristics can be stabilized.

  Although the antistatic electrode is not shown in the plan view of the analog amplification vacuum tube shown in FIG. 1, since the external appearance of the analog amplification vacuum tube is the same, in the following description of the example of the antistatic electrode, AA in FIG. The difference in cross section when cut with a line and the difference in shape on the glass substrate will be described.

<First Example of Antistatic Electrode>
FIG. 8 is a cross-sectional view of the analog amplification vacuum tube of the first example of the antistatic electrode taken along line AA in FIG. FIG. 9 is a diagram illustrating a state in which the anode and the antistatic electrode of the first example are formed on a glass substrate, and FIG. 10 is a diagram illustrating a state of the amplifier circuit. 9 indicates the position of the frame portion 131 of the grid 130 (in other words, the portion facing the frame portion 131). As described above, in the grid 130, the portion of the frame portion 131 may be meshed.

  The entire shaded portion in FIG. 9 is the antistatic electrode 220, and the antistatic electrode 220 may be formed by forming, for example, an aluminum thin film on the entire shaded portion. In the example of FIGS. 8 and 9, the antistatic electrode 220 has a wide range other than a region necessary for ensuring insulation between the anode 120 and the anode 120 on the glass substrate 125 (a range wider than a portion facing the grid 130). ). An insulating film 232 is disposed between the grid support member 133 and the antistatic electrode 220.

In the amplifier circuit of FIG. 10, the antistatic electrode 220 is connected to the ground. The operation as an amplification circuit is the same as that in FIG. 5, but when some of the electrons flowing from the filament 110 side to the anode 120 side reach the antistatic electrode 220, they flow to the ground, so negative charges are charged around the anode 120. Can be prevented. Therefore, the characteristics shown in FIG. 6 can be maintained even when used for a long time. Therefore, the characteristics of the analog amplification vacuum tube 100 can be stabilized.
<Second Example of Antistatic Electrode>
FIG. 11 shows a cross-sectional view of the analog amplification vacuum tube taken along the line AA of FIG. 1 in the second example of the antistatic electrode. FIG. 12 is a diagram illustrating a state in which an anode and an antistatic electrode are formed on a glass substrate, and FIG. 13 is a diagram illustrating a state of an amplifier circuit.

  The difference from the first example is that no antistatic electrode is formed on the portion of the grid 130 facing the frame portion 131. The dotted line in FIG. 12 indicates the position of the frame portion 131 of the grid 130 (in other words, the portion facing the frame portion 131). As shown in FIG. 12, the antistatic electrode 221 has a wide range (grid 130 and a region other than a region necessary for ensuring insulation between the anode 120 and the anode 120 on the glass substrate 125 and a region facing the frame portion 131. It is formed in a wider range than the facing part). In the example of FIG. 12 as well, the antistatic electrode 221 is formed on the entire shaded portion.

  Here, the difference between the second example and the first example will be described. Since the antistatic electrode 220 and the grid 130 face each other, they function as a capacitor. Then, the output impedance R in the previous stage viewed from the grid 130 and the capacitance C between the grid 130 and the ground form an RC circuit, and thus function as a low-pass filter. For example, if the output impedance of the previous stage is 330 kΩ, the capacitance C needs to be 25 pF or less so as not to block a signal in a human audible band (20 Hz to 20 kHz).

  Since the frame portion 131 is plate-shaped (since it is not mesh-shaped), no electrons pass through the frame portion 131. Therefore, the significance of providing the antistatic electrode in the portion facing the frame portion 131 is small in the first place. On the other hand, since it is plate-shaped (since it is not mesh-shaped), if there are opposing electrodes, the capacitance tends to increase. Therefore, it is better not to form the antistatic electrode on the portion facing the frame portion 131 like the antistatic electrode 221, to stabilize the characteristics (antistatic) and prevent deterioration of the characteristics (prevent signal cut-off by a low-pass filter). Easy to balance. However, the antistatic electrode 220 as in the first example or the antistatic electrode 221 as in the second example may be selected in consideration of the output impedance of the previous stage. The electrostatic capacity C between the grid 130 and the ground affects not only the electrostatic capacity between the grid 130 and the antistatic electrode 220 but also the electrostatic capacity between the grid 130 and the filament 110. Attention is also needed.

  In the amplifier circuit of FIG. 13, the antistatic electrode 221 is connected to the ground. The operation as an amplifier circuit is the same as in FIG. 5, but when some of the electrons flowing from the filament 110 side to the anode 120 side reach the antistatic electrode 221, they flow to the ground, so negative charges are charged around the anode 120. Can be prevented. Therefore, the characteristics shown in FIG. 6 can be maintained even when used for a long time. Therefore, the characteristics of the analog amplification vacuum tube 100 can be stabilized.

<Third example of antistatic electrode>
A cross-sectional view of the third example of the antistatic electrode of the analog amplification vacuum tube taken along line AA in FIG. 1 is the same as FIG. FIG. 14 is a diagram illustrating a state in which an anode and an antistatic electrode are formed on a glass substrate, and a diagram illustrating a state of an amplifier circuit is the same as FIG.

  The difference from the second example is that the portion of the antistatic electrode 223 not facing the grid 130 is meshed. For example, a mesh-shaped antistatic electrode such as aluminum having a line width of 0.01 mm and a pitch of 0.3 mm may be used. If the area of the antistatic electrode is reduced to 1 to 20% by using such a mesh shape, the electrostatic capacity can be reduced and charging can be prevented. Since the electrostatic capacitance between the filament 110 and the ground can be reduced, this is effective, for example, when the electrostatic capacitance between the grid 130 and the filament 110 is large. In this example, the antistatic electrode 222 facing the mesh portion 132 of the grid 130 that is easily charged with negative charges forms an antistatic electrode on the entire surface (not in a mesh shape).

  In the amplifier circuit of FIG. 13, the antistatic electrodes 222 and 223 are connected to the ground. The operation as an amplifier circuit is the same as that in FIG. 5, but when some of the electrons flowing from the filament 110 side to the anode 120 side reach the antistatic electrodes 222 and 223, they flow to the ground, so negative charges around the anode 120. Can be prevented from being charged. Therefore, the characteristics shown in FIG. 6 can be maintained even when used for a long time. Therefore, the characteristics of the analog amplification vacuum tube 100 can be stabilized.

<Fourth Example of Antistatic Electrode>
The cross section when the analog amplification vacuum tube of the fourth example of the antistatic electrode is cut along the line AA in FIG. 1 is the same as FIG. FIG. 15 is a diagram illustrating a state in which an anode and an antistatic electrode are formed on a glass substrate, and a diagram illustrating a state of an amplifier circuit is the same as FIG.

  The difference from the second example is that the antistatic electrode 224 is meshed. For example, a mesh-shaped antistatic electrode such as aluminum having a line width of 0.01 mm and a pitch of 0.3 mm may be used. If the area of the antistatic electrode is reduced to 1 to 20% by using such a mesh shape, the electrostatic capacity can be reduced and charging can be prevented. The difference between this example and the third example is that the part of the grid 130 facing the mesh part 132 is also meshed. This is an effective method when it is desired to make the capacitance between the grid 130 and the ground as small as possible.

In the amplifier circuit of FIG. 13, the antistatic electrode 224 is connected to the ground. The operation as an amplifier circuit is the same as that in FIG. 5, but when some of the electrons flowing from the filament 110 side to the anode 120 side reach the antistatic electrode 224, they flow to the ground, so negative charges are charged around the anode 120. Can be prevented. Therefore, the characteristics shown in FIG. 6 can be maintained even when used for a long time. Therefore, the characteristics of the analog amplification vacuum tube 100 can be stabilized.
<Fifth example of antistatic electrode>
FIG. 16 is a sectional view of the analog amplification vacuum tube taken along line AA in FIG. 1 in the fifth example of the antistatic electrode. FIG. 17 is a diagram illustrating a state in which an anode and an antistatic electrode are formed on a glass substrate, and FIG. 18 is a diagram illustrating a state of an amplifier circuit.

The difference from the second example is that no antistatic electrode is formed in a portion not facing the grid 130. That is, the antistatic electrode 222 is formed on a part of the part of the grid 130 facing the mesh part 132 so as to be insulated from the anode. “Partial” means that the antistatic electrode 222 is not formed in a portion where the anode 120 is formed, a region necessary for insulation from the anode 120, or a portion close to the portion facing the frame portion 131. This indicates that not all the portions facing the portion 132 are included. In this example, the antistatic electrode 222 is formed only in a portion facing the mesh portion 132 of the grid 130 that is easily charged with negative charges, thereby reducing the capacitance. Antistatic electrode 222 is formed on the entire surface antistatic electrode (not shaped mesh). If the electrostatic capacity has to be further reduced, the mesh-shaped antistatic electrode 224 may be formed on a part of the portion of the grid 130 facing the mesh portion 132, but the antistatic charge is reduced, though it is small. The effect is obtained.

  In the amplifier circuit of FIG. 18, the antistatic electrode 222 (224) is connected to the ground. The operation as an amplifier circuit is the same as that in FIG. 5, but when some of the electrons flowing from the filament 110 side to the anode 120 side reach the antistatic electrode 222 (224), they flow to the ground, and therefore negatively flow around the anode 120. Charges can be prevented from being charged. Therefore, the characteristics shown in FIG. 6 can be maintained even when used for a long time. Therefore, the characteristics of the analog amplification vacuum tube 100 can be stabilized.

  The above-mentioned example of the antistatic electrode is a variation for solving both the problem of charging and the problem of high-frequency cutoff due to the increase in capacitance. You can choose from. In other words, the present invention is an invention that provides such a degree of design freedom.

<Potential of antistatic electrode>
10, 13, and 18, the antistatic electrodes 220, 221, 222, 223, and 224 are connected to the ground, but may be connected to a positive potential DC voltage source 230 as shown in FIG. 19. What is necessary is just to determine the voltage of a DC voltage source from the range of 0-5V, for example. FIG. 20 shows an example in which a bias power source 330 of the grid 130 is used as a DC voltage source. If the bias power source 330 is used in this way, it is not necessary to increase the types of power sources. FIGS. 19 and 20 are modifications of FIG. 10. If the portion connected to the ground in FIGS. 13 and 18 is connected to the DC voltage source 230 and the bias power source 330 as shown in FIGS. It can be similarly deformed.

The antistatic electrodes 220, 221, 222, 223, and 224 are conductors, but resistance exists, so that potential unevenness occurs on the antistatic electrodes 220, 221, 222, 223, and 224 by simply connecting to the ground, There is a risk of partial negative potential. Then, the anode current _Ia may hardly flow due to the negative potential. If the antistatic electrodes 220, 221, 222, 223, and 224 are set to a positive potential, there is an effect that even if unevenness occurs, a portion having a negative potential does not occur. Therefore, it is possible to prevent a change in the characteristics of the analog amplification vacuum tube due to the negative charge around the anode and to stabilize the characteristics of the analog amplification vacuum tube.

  The resistance varies depending on the material and thickness of the antistatic electrodes 220, 221, 222, 223, and 224, whether they are formed on the entire surface or in the form of a mesh, etc. You can decide.

100,900 Analog amplification vacuum tube 110 Filament 113 Filament support member 120 Anode 121 Anode terminal 122 Anode wiring 125 Glass substrate 130 Grid 131 Frame portion 132 Mesh portion 133 Grid support member 180 Case 220, 221, 222, 223, 224 Antistatic electrode 230, 310 DC voltage source 232 Insulating film 320 Anode voltage source 325 Resistor 330 Bias power source

Claims (6)

A linearly stretched filament that emits thermal electrons;
An anode formed on an insulating substrate disposed in parallel with the filament;
A grid disposed between the filament and the anode to face the anode;
An antistatic electrode formed on the substrate so as to be insulated from the anode;
An analog amplification vacuum tube, wherein the antistatic electrode is connected to a ground or a positive DC voltage source. The vacuum tube for analog amplification according to claim 1,
The grid has a mesh part and a frame part existing around the mesh part,
The antistatic electrode is formed on at least a part of a portion of the substrate facing the mesh portion. An analog amplification vacuum tube. The vacuum tube for analog amplification according to claim 2,
The antistatic electrode is not formed in a portion facing the frame portion. An analog amplification vacuum tube, wherein The vacuum tube for analog amplification according to claim 1,
The antistatic electrode is entirely or partially meshed. An analog amplification vacuum tube. The vacuum tube for analog amplification according to any one of claims 1 to 4,
The antistatic electrode is not formed in a portion that does not face the grid. An analog amplification vacuum tube. The vacuum tube for analog amplification according to any one of claims 1 to 5,
The antistatic electrode is connected to a bias power source of the grid. An analog amplification vacuum tube.

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