US2798903A

US2798903A - Signal amplification system

Info

Publication number: US2798903A
Application number: US215947A
Authority: US
Inventors: Henry M Spencer
Original assignee: Individual
Current assignee: Individual
Priority date: 1951-03-16
Filing date: 1951-03-16
Publication date: 1957-07-09
Anticipated expiration: 1974-07-09

Description

July 9, 1957 H. M. SPENCER SIGNAL AMPLIFICATION SYSTEM 2 Sheets-Sheet 1 Filed March 16, 1951 Henry M. Spe'ner INVENTOR.

2,798,903 Fatented July 9, 1957 SIGNAL AML'MFICATIUN SYSTEM Henry IV. Spencer, Norfolk, Va.

Application March 16, 1951, Serial No. 215347 Claims. (til. 179 471) This invention relates to amplification systems for electrical signals or impulses of all kinds and it has for its main object to provide a simple and eflicient electronic amplification system with a high amplification factor which is free from those defects which usually are inseparable from such arrangements.

Amplification factors which are considerably above those obtainable by the best electronic amplifier arrangements are usually obtained by means of devices producing secondary electrons, the arrangement being such that the ratio of the number of electrons emitted by a cathode and impinging on an electron liberating surface to the number of, secondary electrons which are released from said electron liberating surface is much larger than unity. In such a case the amplification which is obtainable in the amplifier system is of a magnitude which is a product of the amplification obtainable by the system without use of secondary electrons multiplied by a number corresponding to the said ratio.

However arrangements of this type have many inherent disadvantages such as irregular amplification and lack of proportionality, as the secondary electrons repeatedly are drawn away from or deviate from the expected course and special and complex control arrangements for the secondary electrons are therefore necessary. It is therefore an object of the present invention to provide an arrangement using secondary electrons and the multiplication of the amplifying effect produced by such secondary electrons without any special control, collecting or screen ing members.

According to the present invention the electrode of a signal amplifying tube upon which a stream of accelerated primary electrons impinges and from which secondary electrons are emitted or released is not connected with any source of current. It forms with the control element of a further electronic amplifier tube a completely insulated system. It is to be noted that also the control element is without further outer connection so that the flow of secondary electrons is not only controlled by the number of electrons intercepted by said control electrode but also determines the operating potential at which the control electrode is maintained. The number of electrons intercepted by the control element of the further electronic amplifier may thus always be equal or proportional to the number of secondary electrons emitted and ulti mately absorbed by an accelerating target electrode. In this way a completely self-controlled arrangement results which automatically tends to remain in and to return to a stabilized condition.

It is thus a principal object of the invention to provide a reliable amplification system with a high amplification factor which includes a multiplication factor obtained by means of secondary electrons produced in the system and corresponding to a high ratio of released secondary electrons to releasing primary electrons and which is of a simplified type and can dispense with special means for the control of the said secondary electrons.

It is a further object of the invention to provide an 2 amplification system of the above named type in which the multiplication is substantially limited to the signal currents, while the no-signal currents are partly or practically excluded from such multiplication.

It is a further object of the invention to provide special electronic tubes containing the amplification system which tubes may be provided with a common cathode which is surrounded by suitable electron systems permanently connected to obtain the above named results.

Further objects of the invention will be apparent from the following detailed specification.

The invention is illustrated in the accompanying draw-- ings showing several modifications or embodiments of the invention. It is however to be understood that these embodiments of the invention are shown merely by way of example and in order to explain the principle of the invention and the best modes of applying said principle. The invention is only illustrated diagrammatically and the specification does not attempt to describe all the possible modifications embodying the principle of the invention. It will therefore be clear that a departure from the examples illustrated in the drawings is not necessarily a departure from the principle of the invention.

In the drawings:

Figure l is a diagram of the connections illustrating a simplified embodiment of the invention.

Figure 2 is a perspective view illustrating diagrammatically an electronic tube embodying the electrode system according to the invention.

Figure 3 is a further diagram of the connections illustrating another embodiment of the invention.

Figure 4 is a perspective View illustrating diagrammatically an electronic tube with those which have been shown in Figure 3.

Figure 5 is a diagram of a further modification of the invention.

electrode systems Figure 6 is a' perspective view illustrating diagrammatically the electrode systems which have been shown in Figure 5 when enclosed into a single tube.

Figure 7 is a diagram of a further modification of the invention, showing a series arrangement. l

The principle of the invention will be best understood when referring to the simplified arrangement illustrated diagrammatically in Figure 1. This arrangement comprises an electronic tube with two

grids

11, 12 the former being an accelerator grid having the function of accel crating the electrons emitted by the cathode 14 and pass ing the control grid 12 of the electronic tube.

The signal to be amplified and which may be of any character is received'at the terminals 3, 4 and is transmitted by means of an input transformer 13 to the control grid 12 and cathode 14 respectively.

The accelerator grid 11 is connected with the positive side of a high tension battery 2% by means of conductor 24 and the negative side of the battery is connected with the cathode 14 by means or a suitable resistor 19.

The plate 15 of the tube 10 is directly connected by means of conductor 29 with the control grid 31 of second electronic tube 26 having a cathode 25 connected with the negative side of the battery 20 by means of a conductor 23 over the resist0r 19. The cathodes 14 and25 have the same potential as will be seen from the diagram.

The plate 15 has no battery connection and may'con- T tain a material favoring the emission of secondary electrons or may be made of such a material or may be coated Which the apparatus or device for receiving the amplified signals is'connected'.

The electrode systems of the tube or tubes and 26 cooperate in the following manner.

Let it be assumed that electrons, the number of which is controlled by the signal voltage arriving at the terminals 3 and 4 and transmitted to the control grid 12, move towards and are accelerated by the high positive voltage on the acceleratorgrid 11. These electrons will pass through the grid and will impinge upon the plate 15. The plate in this case is not connected with any source of definite potential. Secondary electrons will be released from or will be knocked off the plate 15 whenever an electron coming from the cathode and accelerated by the grid 11 strikes the plate 15 and the number of secondary electrons thus released should be greater than the number of electrons impinging upon the plate. All secondary electrons will be attracted to the acceleator grid 11 which has the highest positive potential and they therefore Will move towards said grid. Thus the plate 15 constantly loses more electrons than it gains and for this reason it will become more and more positive. As the plate 15, the conductor 29 and the control grid 31 of tube 26 forms a single insulated system which acts as an inter-system control, this system will become more positive when more electrons are accelerated by the accelerator grid 11. The number of electrons moving towards the accelerator grid depends on the number of electrons which are permitted to pass the control grid 12 which, in its turn, is influenced by the magnitude of the signal voltage. It will thus be clear that the voltage on plate will be multiple of the incoming signal voltage and that the amplification factor will not only include the conventional amplification factors but Will also include a multiplication factor expressing the relation between the number of accelerated primary electrons and the number of released secondary electrons. The conventional amplification factor also includes the amplification obtained in the tube 26. As the ratio between primary and secondary electrons may be high the gain obtainable with the arrangement as above described, will be correspondingly high and will be much higher than the gain which is obtainable with conventional arrangements.

When the signalvoltage is lowered the number of primary electrons impinging upon the plate element 15 is reduced and the number of secondary electrons released from plate 15 is reduced correspondingly. The

plategrid systems

15, 31 therefore becomes increasingly negative and therefore the output current in tube 26 also drops correspondingly. It will thus be clear that the plate current of tube 30 always varies with the signal current.

The arrangement, as described, forms a coupling between the two electrode systems in the

tubes

10 and 26 which so interlinks the said electrode systems that they act merely as the components parts of a single system.

In order to maintain the described operation it is necessary that the number of electrons intercepted by grid 31 of tube 26 during operation must always be such that the flow of secondary electrons from plate 15 toward the accelerator grid 11 is maintained. It is also clear that it may be of advantage to operate the system with a constant negative charge of the electrode systems 1529--31, provided the dimensions of the tubes and spacing of the electrodes etc. permits operation with a negative grid bias on grid 31.

The above described system is therefore an amplification system with secondary electron emission permitting to obtain an amplification factor which is much higher than that obtainable in systems operating with the electrons emitted from the cathode, while at the same time the system according to the invention preserves the character of a completely controlled and stable system.

In the diagram shown in Figure 1 two separate electronic tubes connected in a suitable manner are illustrated which tubes may be suitably selected from existing types. However, it may be of advantage to construct a special tube for the system which has been described above and in this case it is preferable to arrange the electrode systems, corresponding to those of the

tubes

19 and 26 in the diagram, within one and the same bulb and to use common electrodes wherever possible.

Figure 2 shows a special tube of this type. It comprises the conventional sealed and evacuated glass envelope 55. which is mounted on a base or socket 56. Within the evacuated bulb the cathode 33 is arranged which may be a common element of the electrode systems. The cathode may be of the type heated by a special internal filament (not shown) the two ends of which are indicated at 34 and 35. The filament is connected by means of

wires

36, 37 with base pins 38, 39. The cathode cylinder itself is connected by means of wire 5th to the base pin 51.

In Figure 2 the upper electrode system corresponds to the system indicated by the

reference numerals

12, 11 and 15 in Figure 1. It comprises a control grid 40 and the accelerator grid 42 (corresponding to grid 11 in Figure 1) which grids are both shown in the formof a spiral.

The control grid 40 may be connected with an upper grid cap 44 arranged on top of the evacuated glass bulb while the accelerator grid 42 is connected by means of wire 48 with a base pin 49.

The two grids are surrounded by the cylindrical plate 45 (corresponding to plate 15 in Figure 1). All these, elements surround the upper portion of the cathode 33.

The second electrode system surrounds the lower portion of the cathode cylinder 33 in Figure 2 and it corresponds to the

electrode system

31, 30 in Figure 1. It comprises a grid 58 (corresponding to grid 31 in Figure 1) having theconventional spiral shape and the cylindrical anode 60 (corresponding to anode 30 in Figure 1). The

grid 58 is directly connected with the plate 45 of the first: electrode system by means of wire 61 while the plate 60.

is connected with one "of the base pins 63.

The electronic tube illustrated in Figure 2 is thus a full equivalent to the arrangement with two electronic discharge tubes.

In the arrangement shown in Figures 1 and 2 the amplification obtained by means of electron multiplication.

due to the liberating of secondary electrons by impact is applied to the total current passing through the electrode systems'which includes the no-signal current as well as the signal current. It is however clearly an advantage to amplify the signal currents by multiplication either without amplifying the no-signal current or by amplifying,

(Figure 3) the control grid 12 and an accelerator grid' 11 and-plate 15. The control grid is connected with the. secondary of the input or signal transformer 18 whichis fed by thesignal currents at the terminals 3 and 4. The accelerator grid 11 is connected with a high tension battery 20 by means of conductor 24 and the plate 15 is connected with the control grid 31 of tube 26 as before described and forms with it an insulated inter-system control while the plate 30 of the tube 26 is connected with the high tension battery 20 over the secondary 28 of the output transformer.

In addition to the aforedescribed members and electrode systems, identical with those already described in connection with Figure 1, a further set of electrodes 2],

17, 16 are added, one of said electrodes being a cathode 21 connected with the other cathodes 14- and'25 of the other electrode systems, while the electrode 16 is a grid which is connected with the plate-grid systems 15-31.

The third electrode of the system. is. a plate 17. connected with connection 24 leading to the high tension battery 20.

The plate voltage applied to plate 17 must be such that all the electrons emitted by the cathode are attracted towards it so that the entire electron cloud surrounding the cathode is completely dissipated. The electrode system is thus operating at the saturation point. The number of electrons attracted towards the plate is thus always the same regardless of the voltage fluctuations which may occur by virtue of the connection of the grid 16 with the conductor 29 of the plate-

grid system

15, 31. Likewise the number of electrons intercepted on the grid 16 will always be the same or nearly the same and this number is preferably made equal to the number of secondary electrons which were attracted towards the accelerator grid 11 and which corresponds to the electron flow making up the no-signal current component. Therefore the remainder of the system which works approximately. in the manner which has already been de scribed in connection with Figure 1 uses the multiplication by means of secondary electrons solely for the purpose of multiplying the signal current plus a fraction of the no-signal current which may be made as small as practicable. The voltage of the three electrodes 11, i6 and 31 is always equal and it is determined by the control grid 12 of the first electronic tube 10 which controls the current flowing through this tube towards the plate 15.

The three electrode systems may again be enclosed within and form part of a single electronic tube shown diagrammatically in Figure 4. The parts corresponding to those already described in connection with Figure 3 are designated by the same reference numerals and their operation therefore need not be described.

The multiple electronic tube illustrated in Figure 4 comprises the evacuated bulb or envelope 55 carried by a socket 56 which is. provided with a number of base pins and with a grid cap 44 on the top of the bulb connected with a sealed in connection in the top of the bulb.

The electrode system consists of the cathode 33 which forms the common element of all electrode systems and which is heated by a heater filament (not shown) the ends 34, 35 of which project from the cathode cvlinder and are connected with base pins 38, 39 by means of the sealed in

wires

36, 37. The cathode cylinder itself is connected with a base pin 51 by a sealed in wire 50.

The cathode is surrounded by a first electrode system which consists of the control grid 40, connected with the grid cap 44 at the top of the bulb 55, of an accelerator grid 42 and of a plate 45. The second electrode system (the lowermost system in Figure 4) consists of grid 5% and plate 60 the latter being connected by means of a sealed in wire with base pin 63.

Between the two above described systems a third electrode system is arranged which surrounds the common cathode 33 and which consists of grid 65 which has the shape of a spiral wire and which may be directly joined at 68 to grid 58 of the lower system on one side and to plate 45 of the upper system at 69 on the other side. A plate 66 is connected with the accelerator grid wire 48 leading to base pin 49 and is further connected with the accelerator grid 42 of the upper system by means of a short connection wire '71.

A simplified arrangement of the type illustrated in Figure 3 is shown diagrammatically in Figures 5 and 6. The reference numerals which are identical with those used in Figures 3 and 4 indicate parts which are the exact equivalents to those already described.

The diagrams in Figures 5 and 6 differ from those above described mainly by the fact that the third electrode system consists merely of a collector electrode in the shape of a plate or a ring 70 (Figure 5) indicated at 75 in Figure 6. In Figure 5 the collector electrode is shown as a plate facing the cathode 21 in a separate evacuated bulb in the manner of a diode and, in fact, a diode of an existing type may be used for this purpose. In Figure 6 the collector electrode is shown as a ring 75 arranged between the two

electrode systems

40, 42, 45 and 58, 60. The collector ring is in this case connected with the conductor 29 of the plate-grid system 15, 31 (Figure 5) and in the arrangement shown in Figure 6 the ring 75 is joined to the

electrodes

45 and 58 by short connecting

pieces

76, 77. The collector electrode is therefore not directly joined to a positive potential, but is joined to a system which in order to make it operative, must always be positive to a desired extent. This arrangement is therefore dependent on suitable dimensions and current and voltage values.

Essentially however the operation is the same as that already described in connection with Figures 3 and 4. The collector ring '75 must be charged with a positive potential which is capable of drawing towards it all the electrons emitted by the cathode 21 whatever the fluctuation of the said potential so that the electron cloud is completely dissipated and the saturation point is reached. Regardless of such fluctuations the number of electrons drawn towards the collecting electrode is substantially constant and does not vary with the signal fluctuations. The number of electrons collected on the electrode must be equal to the number of secondary electrons in the current flow between electrodes 15 and 11 (42 and 45 in Figure 6) corresponding to the constant nosignal current. The remainder of the system operates substantially as an electron multiplier system for the signal currents, as only a small fraction. of the Ito-signal current is amplified by these means. The dimensions of the collector electrode or ring must of course be chosen correspondingly and they are preferably so selected that the collector '70 very nearly but not fully supplies the plate 15 with electrons in replacement for those which have been knocked out by the impact of the primary electron stream. The

electrodes

15, and 30 will then, be sulficiently positive to make the grid 31 intercept the number of electrons which corresponds to the diiierence.

It will be seen from the above description that the system described is a very eificient amplification system with a high amplification factor which is finely adjustable. The system is free of all those irregularities which in most electron multiplying arrangements are inseparable from such devices and which cause a non-linear response and non-uniform amplification and a distortion of the output unless special means are provided to suppress these effects. The system as described may use suitable tubes such as existing and as marketed. The tubes may have any number of grid electrodes when a suflicient number of types of multi-grid tubes is available to select suitable tubes for the purposes of this invention from them. The additional grids arranged in the electrode systems between the control grid and the acceleration grid may be used in any well known manner as the present invention does in no way affect their operation. The same may be said of grids inserted between the control grid of the second tube and the plate. The electrode system of the last tube may of course also be that of a beam power tube.

It will also be understood tht the system according to this invention, for instance the system illustrated in Figures 1 and 2 may consist of more than two electrode systems with several tetrodes, such as tube 1%), arranged in series (Figures 7). The plate 15 of the first electrode system of the series is in this case connected with the control grid 41 of a further tetrode Sit, the plate 47 of which may again be connected with the control grid of the next tetrode if the series should consist of more than two tetrodes. The plate of the last tetrode (47 in Figure 7) is then connected with the control grid 31 of the

electrode system

25, 31, 36 which is connected with the output transformer. The accelerator grids d3 of the ad ditional tetrodes of the series are all connected with condoctor 29 leading to the positive side of the battery. The

electrode system 25,'31,'30 is shown as a triode, but may have any number of grids connected in the conventional manner. In addition as shown in 'Figure7,

electrode systems

21, 16, 17 similar to those described in connection with Figure 3 or electrode systems 21, 70 such as shown in Figure 5 may be inserted.

Further it will be understood that unessential details may be changed without departing from the essence of the invention as defined in the annexed claims.

"Having described the invention, What is claimed as new is:

-l. An electronic amplifying system, comprising a plurality of electrode systems, each having a source of primary electrons forming the cathode, a source of current for providing the no-signal current of the system, a first one of the systems being a tetrode system including a control grid, connected with a signal input circuit, a combined electron accelerating target electrode connected with a source of positive voltage of the said source of current, and a plate adapted to emit secondary electrons upon impact of primary electrons on the same which have been accelerated by the accelerating and target electrode, the surface of the secondary electron emitting plate and the accelerating and target electrode facing each other di-- rectly. a diode system and a triode system, the latter ineluding a control grid, and the diode system including a collector electrode facing the cathode of the diode system, the control grid of the triode system and the collector electrode being both directly and exclusively connected with the plate emitting secondary electrons and forming with the said plate an otherwise insulated system, the diode system being dimensioned to produce operation at the saturation point with the positive voltage imparted to it, an anode in the triode system connected with a positive voltage furnished by the source of currents, the positive voltage being so adjusted that the number of electrons intercepted at the control grid of the triode system corresponds to the number of secondary electrons emitted by the plate of the tetrode system which are due to the nosignal current, an output circuit connected to the anode of the triode sysem, the amplification of the signal current in the output circuit being thus proportional to the product of the tube amplification factor and the ratio of primary and secondary electrons, while the nosignal current amplification is constant and is equal to a predetermined fraction of the no-signal current.

2. An electronic amplifying device comprising a plurality of coaxially aligned cylindrical electrode systems. arranged in one common evacuated envelope, all systems having a common central cathode emitting primary electrons, a first one of said systems includinga control grid surrounding the cathode, an independent outer cylindrical plate electrode, the inner surface of which directly faces and surrounds a combined electron accelerating and target forming grid electrode which surrounds the said control grid and cathode and is unconnected with the plate which surrounds it, said plate electrode being adapted to emit secondary electrons upon impact of primary electrons; a second one of said coaxially located aligned elec trode systems including a second control grid surrounding the cathode, directly connected with the plate electrode of the first system and forming with said plate electrode an insulated otherwise unconnected system forming an inter-system control, an anode surrounding the control grid of the said second one of the electrode systems, terminal connections for the anode, for the cathode, for the control grid and for the accelerator and target electrode of the first one of the electrode systems, and a further electrode system surrounding the cathode consisting of a collector ring, said collector ring being connected with the insulated otherwise unconnected plate-control grid system forming an inter-system control and being inserted between said first one and'the second one of the electrode systems. I

3. An amplification system for signal currents comprising a source of currents, a plurality of electronic discharge .tube electrode systems each containing a cathode forming a source of primary electrons, the cathodes of. all electrode systems being connected to a common reference system; the first one of said-electron systems including in addition a control electrode, means to impose a signal on said control electrode, an accelerating electrode for the primary electrons emitted by the cathode, said accelerating electrode being connected with a. positive voltage supplied by the source of current, and a plate electrode adapted to emit secondary electrons upon bombardment with theprimary electrons, which plate electrode faces said accelerating electrode and is unconnected with any other electrode of its system; a second one'of said electrode systems including an anode connected with the positive side of the source ofcurrent and also with an output circuit and further including a control grid which is connected with the plate electrode of the first one ofthe electrode systems and forms with it an insulated inter-system control, the primary electrons emitted by the cathode of the first one of the electrode systems and impinging upon the plate electrode of the first one of said systems, producing secondary electrons attracted to the accelerated electrode as the target electrode, the change of voltage due to the signal producing a fluctuation of the primary electrons and a corresponding fluctuation of the emission of secondary electrons on the plate electrode entailing a change of voltage in the inter-system control controlling the output circuit of the second one of the electrode systems; a third one of said electrode systems including an electrode connected with the aforesaid inter-system control, the last named electrode of the third electrode system being dimensioned relatively to another electrode of the same system for operation on the saturation point attracting permanently all the electrons produced within said third electrode system, said first system thus providing the inter-system control with a number of electrons which is in a predetermined relation to the number of primary electrons producing a no-signal current in the first electrodesystem.

4. An amplification system for signal currents comprising a source of currents, a plurality of electronic discharge tube electrode systems each containing a cathode forming a'source of primary electrons, the cathodes of all electrode systems being connected to a common reference system; the first one of said electron systems including in addition a control electrode, means to impose a signal on said control electrode, an accelerating electrode for the primary electrons emitted by the cathode,-said accelerating electrode being connected with a positive'voltage supplied by the source of current, and a plate electrode adapted to emit secondary electrons upon bombardment with the primary electrons, which plate electrode faces said accelerating electrode and is unconnected with any other electrode of its system; a second one of said electrode systems including an anode connected with the positive side of the source of current and also with an output circuit and further including a control grid which is connected with'the plate electrode of the first one of the electrode systems and forms with it an insulated inter-system control, the primary electrons emitted by the cathode of the first one of the electrode systems and impinging upon the plate electrode of the first one of said systems, producing secondary electrons attracted to the accelerated electrode as the target electrode, the change of voltage due to the signal producing a fluctuation of the primary electrons and a corresponding fluctuation of the emission of secondary electrons on the plate electrode entailing a change of voltage in the inter-system control controlling the output circuit of the second one of the electrode systems; a third one of the electrode systems including a control electrode and an anode, the latter connected with the positive side of the source of current, while the last named control electrode is connected with the inter-system control connecting the plate of the first one of the electrode systems and the control grid of the second one of the electrode systems, said anode of the third one of the electrode systems and the control electrode of the same system being dimensioned and the voltage supplied to the anode being selected to produce operation of the third electrode system at the saturation point, said anode of the third electrode system attracting permanently all the electrons produced in said third electrode system, the latter thus providing the inter-system control with a number of electrons which is in a predetermined relation to the number of primary electrons producing a no-signal current in the first system.

5. An amplification system as claimed in claim 4 wherein the third one of the electrode systems consists of a diode.

References Cited in the file of this patent UNITED STATES PATENTS Jonker etal Jan. 31, 1939 Jonker et al. Feb. 7, 1939 Rinia Dec. 24, 1940 Eaglesfield Dec. 31, 1940 Skellett Sept. 21, 1943 Strutt et al. Jan; 13, 1948 Van Weel Feb. 14, 1950 Atherton May 22, 1951 FOREIGN PATENTS France Aug. 9, 1937 France Apr. 11, 1939 Australia Dec. 6, 1939