US2721951A

US2721951A - Low reactance electron discharge device

Info

Publication number: US2721951A
Application number: US203306A
Authority: US
Inventors: Cohen Robert Matthew; Prager Hans John
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1950-12-29
Filing date: 1950-12-29
Publication date: 1955-10-25
Anticipated expiration: 1972-10-25

Description

Oct. 25, 1955 R. M. COHEN ET AL LOW REACTANCE ELECTRON DISCHARGE DEVICE Filed Dec. 29. 1950 A ORNEY United States PatentO LOW REACTANCE ELECTRQN DISCHARGE DEVICE Robert Matthew Cohen, Eeileviile, and Hans John Prager, Maplewood, N. L, assignors to Radio Iorporation of America, a corporation of Deiaware Application December 29, 195%), Serial No. 203,356

Claims. (Cl. 313-239) Our present invention relates to electron discharge devices and more particularly to a triode form of such devices'having a desirable high signal to noise ratio and reduced objectionable reactance elfects.

Accordingly, it is an important object of the invention to provide an improved electron discharge device of relatively high signal to noise ratio and without objectionable reactance elfects.

Another object is to provide a triode electron discharge device useful over a relatively 'wide band of frequencies without undesired reactance effects.

A further object is to provide an electron discharge device including a triode having fixed reactance neutralization means effective for each of a plurality of assigned television broadcast channels.

Another object is to improve reception of television signals.

A further object is to improve television reception with indoor or built-in antennas.

Another object is to improve television reception in fringe areas.

According to one aspect of the invention, the capacitance between the cathode and anode of a triode is reduced. This is accomplished by utilizing a double triode in one envelope, the grid of one of the triodes, which may be termed the input triode, serving as the input electrode, and the anode of the other or output triode functioning as the output electrode. The anode of the input triode is connected to the cathode of the output triode. The grid of the input triode serves as the signal input; the grid of the output triode is connected to ground since the output unit is operated as a grounded-grid amplifier.

The only capacitive neutralization required in connection with the grounded grid output triode is that of its anode-to-cathode capacitance. According to the invention by the use of a novel basing arrangement which serves to reduce the capacitance between the cathode and anode lead-ins of the output triode, neutralization of this triode is unnecessary.

However, neutralization of undesirable reactance elfects in the input triode of the device is required even with a minimum obtainable anode-to-grid capacitance of this triode. The complexity and difiiculty in accomplishing the desired neutralization are appreciably reduced according to the invention. The capacitive component of the undesired reactance is between the anode of the input triode and ground and physically consists in part of the anode-to-cathode capacitance and in part of the capacitance associated with the tube lead-ins. The anodeto-cathode capacitance is determined by the anode area, the cathode area, the spacing between the anode and cathode, and the lead-in capacitance by the lead-in from a socket terminal to the anode. This capacitive component, particularly that due to lead-in connections, is reduced according to the invention.

The inductive component of the undesired reactance affects both triodes of the device. The source of undesirable inductive reactance physically consists of the leads from tube terminals to the anode of the input triode and to the cathode of the output triode. According to the invention, this reactance is reduced to a minimum by using an internal connection between the anode of the input triode and the cathode of the output triode.

The aforementioned aspects of the invention render the use of this triode in a television receiving system advantageous by providing for neutralization of objectionable reactance etfects characteristic of triodes, that is effective for each of the television transmitting channels Without requiring adjustment on tuning the receiver from one channel to another. Consequently, the invention makes it feasible to obtain the relatively high signal to noise ratio characteristic of triodes without the limitation of the prior art as to neutralization. A circuit with which the device of the invention may be used to advantage is described in .co-pending application Serial No. 230,945 filed June 11, 1951, by Robert Matthew Cohen and assigned to the same assignee as the present application.

While British Patent 444,559 shows a double triode electron discharge device in which the anode of one of the triodes is connected to the cathode of the other, the arrangement therein described is not capable of securing the relatively high order of shielding of the input triode from the output triode that is characteristic of our invention. This is for the reason that the British patent referred to appears to be indifferent as to the basing arrangement employed and fails to suggest the advantage of an electrostatic shield between the mode assemblies. While an internal connection between the anode and cathode referred to contributes some reduction in reactance between the triodes, appreciably greater reduction in reactance is accomplished by the novel combination of such internal connection with an electrostatic shield between the triodes and a novel basing arrangement according to our invention.

While the invention is pointed out with particularity in the appended claims, it may best be understood from a detailed description of embodiments thereof taken in connection with the appended drawing, in which:

Figure l is anelevation partly in section of an electron discharge device incorporating the invention;

Figure 2 is an enlarged cross-section along the line 22 of Figure l and shows the electrode arrangement of the device;

Figure 3 is an enlarged view partly in cross-section along the line 3-3 of Figure 1 and shows the connections of the electrodes to their respective lead-ins, whereby terminals of appreciable signal voltage ditference are shielded, and the anode of one electrode unit and the cathode of the other unit are connected together within the device and having no lead-ins to input plate or output cathode.

Figure 4 is a schematic representation toillustrate the advantages obtained from the internal connections between a cathode and anode of the device, as shown in Fig. 3, and from the novel basing arrangement of the invention;

Figure 5 is a schematic representation of a modification in which the internally connected cathode and anode are connected to a common lead-in and in which the novel basing arrangement of the invention is employed;

Figure 6 is a schematic showing of a further modification where a cathode and anode of the device are connected to individual lead-ins, the lead-ins referred to being connected together externally of the device, and wherein the novel basing arrangement of the invention is used.

Referring now in more detail to the drawing, there is shown in Figures 1, 2 and 3, an electron discharge device embodying a preferred form of our invention. Within an envelope 10, closed at one end by a stem 11, are disposed two electrode assemblies 12, 13 between which is positioned an electrostatic shield 14. Each of the electrode assemblies comprises a triode. The triode of assembly 12 includes a cathode 15 having a heater 16, a grid 17 supported on grid side rods 18, 19, and a tubular anode 20 having apertures 21 in the opposite walls thereof. The apertures are provided for visual inspection of the inner electrodes and for blowing lint from the interior cavity of the anode. The anode may have

flanges

22, 23, as shown in Figure 2, for structurally ruggedizing the device and for added heat dissipation. The electrodes are supported between two

insulating spacer plates

24, 25 which may be of mica.

The electrode assembly 13 includes a cathode 26 having a heater 27, a grid 28 supported on

grid side rods

29, 30, and an anode 31. These electrodes are similar to the electrodes of assembly 12 and are also supported between

insulating spacers

24, 25.

Each of the electrodes referred to as well as the shield 14, have portions thereof extending below the lower insulating spacer 25, as shown in Figures 1 and 3. Some of these portions are connected directly or by means of connectors, to suitable lead-ins to be described below.

According to the invention, a triode electron discharge device is provided having inherently characteristics that provide for a high signal to noise ratio and including an electrode arrangement and basing array for accomplishing an external neutralization of undesired reactance effects at a plurality of different frequencies, without requiring adjustment of the neutralization for each frequency.

The electrode arrangement of the invention as aforementioned includes two triodes 12, 13 in one envelope. Triode 12 serves as the input of the device and triode 13 as the output. The grid 17, is used as the input terminal and grid 28 of the output triode is operated at ground potential as schematically shown in Fig. 4. The anode 20 of the input triode is connected to the cathode 26 of the output triode. This accomplishes a reduction in capacitance, since it eliminates the capacitance that woud otherwise occur between the lead-in or lead-ins to which one or both of these electrodes would be connected and ground.

The embodiment of the invention shown in Figures 1, 2 and 3, in which the anode of the input triode is internally connected to the cathode of the output triode and neither of these electrodes is connected to a leadin, is preferred for several reasons. The absence of a lead-in to either of the electrodes mentioned avoids undesirable capacity effects between these electrodes and ground. Such capacity effects are caused predominantly by the fiat and relatively wide contact members used in sockets in which prongs of the device are inserted when the device is associated with a circuit. Such capacity effects are from 2 to 3 micro-microfarads for each socket contact member. Consequently the elimination of a lead-in from both of the electrodes referred to avoids connection of these electrodes to such contact members, and reduces appreciably the capacitance of said electrodes to ground. Furthermore, the relatively short lead 32 required for accomplishing the internal connection between the anode and cathode referred to, greatly reduces undesirable inductance 33, as shown in Figure 4 in dotted lines. It will be obvious that a longer lead, such as would be required if these electrodes were connected to one or more lead-ins, would be characterized by an appreciable increase in inductance.

It will be appreciated, therefore, that the internal connection between the anode 20 and the cathode 26, appreciably reduces undesirable reactance of the device and contributes to ease of neutralization of the device over the wide frequency range required.

In addition to reducing the capacitance between leadins and inductance in connecting leads, the electrode arrangement referred to also serves to reduce the capacitance between the output cathode 26, and the output anode 31 which permits the output section to operate without neutralization. If the device, therefore, is used in a circuit whereby the input is applied to grid 17, and the output is taken from anode 31, an appreciable reduction in capacitance and inductance between the inter-connected electrodes of the device is accomplished by the electrode arrangement of the invention.

According to a modification, as shown schematically in Figure 5, the anode 20 of the input triode is connected within envelope 10 to the cathode 26 of the output triode, and in addition both of these electrodes are connected to a lead-in 39 by means of a lead 39a. In this modification, a partial advantage of the invention is realized. This advantage is the reduction in the capacitance to ground of the input anode and the output cathode, previously described. However, as a result of anode 20 and cathode 26 being connected to a lead-in of the device, some capacitance as shown at 44 in dotted lines will occur between this lead-in and ground. Furthermore, the longer lead 39a will have more inductance shown in dotted line 45, than the shorter lead 32 of Figure 4.

According to a further modification of the electrode arrangement of the invention as shown in Figure 6, the anode 20 of the input triode 12 and the cathode 26 of the output triode 13 are connected to separate lead-

ins

36, 39 respectively. In this modification, the lead-

ins

36, 39 are connected together by means of a circuit 43 external of the device 10. This arrangement introduces some undesirable capacity effects shown in dotted lines 46, 47 between the lead-

ins

36, 39 and ground, and increased inductance 48 shown schematically.

The basing arrangement according to the invention serves to effectively reduce the reactance of certain critical lead-ins of the device and between said lead-ins and ground. This is of particular advantage in the arrangements illustrated in Figures 5 and 6 wherein the cathode 20 and anode 26 are connected to one or more lead-ins. It is also of advantage in the preferred arrangement shown in Figure 3 in that it contributes to a further reduction in the capacity effects of the device.

The basing array of the invention may be used in an electron discharge device having nine lead-ins or pins 34 to 42, as shown in Figure 3, and provides effective shielding of lead-ins of high signal voltage difference from each other to thereby neutralize reactance effects therebetween.

Referring first to the basing arrangement of Figure 3, wherein the anode 20 and cathode 26 are internally connected to each other and free from connection to a lead-in, anode 31 of the output triode is connected to pin 34 and the signal grid 17 is connected to pin 40. The

pins

34 and 40 which in this modification are characterized by a relatively high signal voltage difference, are separated by pin 42 connected to electrostatic shield 14. Furthermore, on one side of heater pin 37 is a pin 36 not connected to any electrode within the device. This effectively aids in shielding the other pins from the heater pins 37, 38.

In the arrangement shown in Figure 5, the pin 34, connected to output anode 31 is effectively shielded from pin 39 connected to the output cathode 26 and input anode 20, by

pins

41 and 42 which are normally grounded. In addition pin 35 connected to grounded grid 28 and free pin 36, effectively shield pin 34 from the heater pins 37, 38.

The basing arrangement shown in Figure 6 is similar in most respects to that of Figure 5. It differs therefrom solely in that the hitherto unused pin 36 is connected to cathode 26 of the output triode. The shielding between

pins

34 and 39 of high voltage difference is accomplished as before by pin 42 connected to shield 14. Shielding is also contributed, as in Figures 3 and 5, by pin 35 connected to grounded grid 28. In the arrangement of Figure 6, pin 35 shields pin 34 from pin 36.

In each of the modifications referred to therefore effective neutralization of a device is accomplished by a novel basing array incorporated in the device.

It will be appreciated from the foregoing that we have provided a novel electron discharge device of the triode type for high signal to noise ratio without the disadvantage of frequency-critical neutralization. The reduced reactance in the plate lead-ins provided by the novel electrode arrangement and the improved shielding resulting from the basing array of the invention is effective over a relatively wide band of frequencies and therefore renders the device admirably suited for use in television reception.

Various modifications may be made in the invention by persons skilled in the art without departing from its spirit, and it is desired to include such modifications within the scope of the appended claims.

We claim:

1. An electron discharge device comprising an envelope closed at one end by a stern, nine lead-in conductors disposed in a circular array and extending through said stem, electrode elements including a cathode, a heater connected to two adjacent ones of said conductors, two others of said elements being connected by a lead to each other and being free from connection to any of said lead-in conductors, the other electrode elements being connected to five others of said conductors adjacent each other whereby two of said conductors are free from connection to an electrode element, said lead being adjacent said two of said conductors said two of said conductors being disposed between the group of said two adjacent conductors and the group of said five adjacent conductors for electrostatically isolating said two adjacent conductors from said five adjacent electrodes, and a shield adjacent said lead and adapted to have ground potential, whereby the inductance of said lead and capacitance effects between said elements are reduced for improved utility of said device over a relatively wide band of frequencies.

2. An electron discharge device comprising an envelope closed at one end by a stem, a plurality of lead-in conductors disposed in a circular array and extending through said stem, a plurality of electrode elements within said envelope, one of said elements comprising a cathode heater connected to two adjacent ones of said conductors, two others of said elements being connected by a lead to each other and being free from connection to any of said lead-in conductors, still others of said electrode elements being connected to others of said conductors adjacent each other, two others of said conductors being free from connection to an electrode element, said lead being adjacent said two of said conductors, said two others of said conductors being disposed between the group of said two adjacent conductors and the group of said others of said conductors for electrostatically isolating said two adjacent conductors from said others of said conductors, and a metal shield adjacent said lead and between groups of said electrode elements, said shield being adapted to have ground potential, whereby the inductance of said lead and capacitance effects between said last named groups of electrode elements are reduced for improved results of said device over a relatively wide band of frequencies.

3. An electron discharge device comprising an envelope closed at one end by a stem, a plurality of lead-in conductors disposed in a circular array and extending through said stem, a plurality of electrode elements within said envelope, one of said elements comprising a cathode heater, a second and third of said elements being connected to each other and being free from connection to any of said lead-in conductors, two of said lead-in conductors being free from connection to any of said electrode elements, two others of said lead-in conductors being adjacent each other and connected to said heater, the others of said electrode elements being connected to the others of said lead-in conductors, said two of said lead-in conductors being disposed between the group of said two others of said lead-in conductors and the group of said others of said lead-in conductors for electrostatically isolating said two others of said conductors from said others of said conductors, and a shield adjacent said lead and adapted to have ground potential, whereby the inductance of said lead is reduced for improved utility of said device over a relatively wide band of frequencies.

4. An electron discharge device comprising an envelope closed at one end by a stem, a plurality of lead-in conductors disposed in a closed array and extending through said stem, a plurality of electrode elements within said envelope, a lead between two of said elements, and a metal shield adjacent said lead, said two of said elements being free from connection to any of said conductors, two of said conductors being free from connection to any of said elements, two adjacent ones of said conductors being connected to one of said elements, the others of said conductors being connected to the others of said elements, said two of said conductors being disposed between the group of said two adjacent ones of said conductors and the group of said others of said conductors for electrostatically isolating said groups from each other, whereby said device is characterized by improved utility over a relatively wide band of frequencies.

5. An electron discharge device useful over a relatively wide band of frequencies and comprising an envelope closed at one end by a glass stem, a cathode heater in said envelope, two adjacent lead-in conductors connected to said heater, two other lead-in conductors being free from connection to any element within said envelope, two electrode elements within said envelope being free from connection to a lead-in conductor, a lead electrically connecting said two elements, a shield adapted to have ground potential adjacent said lead for reducing the inductance of said lead, and a plurality of other lead-in conductors connected to a plurality of other electrode elements within said envelope, said two other lead-in conductors being disposed between two groups of said conductors, one of said groups including said two adjacent conductors and the other of said groups including said plurality of other conductors, whereby said groups are electrostatically isolated from each other.

References Cited in the file of this patent UNITED STATES PATENTS 1,925,558 Foster Sept. 5, 1933 2,118,866 Schlesinger May 31, 1938 2,178,747 Espe Nov. 7, 1939 FOREIGN PATENTS 444,559 Great Britain of 1936 547,646 Great Britain Sept. 4, 1942 526,294 Germany June 4, 1931