US2313886A - Electronic valve device - Google Patents

Description

March 16, 1943. N ET 2,313,886

ELECTRONIC VALVE DEVICE Filed July 24, 1941 2 Sheets-Sheet 1' slbn'al Source ELECTRONIC VALVE DEVICE Filed July 24, 1941 {Sheets-Sheet 2 I Pic-32b.

i wi U Kg U 2 Patented Mar. 16, 1943 ELECTRONIC VALVE DEVICE raul Nagy, Richmond, and Marcus James Goddard, Newberry, England I Application July 24, 1941, Serial No. 403,914 In Great Britain January 15, 1940 17 Claims.

The present invention relates to electronic valve devices, for example thermionic valves, suitable for amplifying low intensity variations of electric potential and like purposes. More particularly it relates to such devices employing an electron beam focussed to form an electron image of limited dimensions as in cathode ray tubes.

According to conventional practice in thermionic valve technique, a cathode, inclosed in an evacuated container, is heated directly or indirectly so as to emit electrons, while an anode, at a positive potential relative to the cathode, collects the emitted electrons. I

Except in the case of the diode rectifier, at least one other electrode, called a grid, is emcross section.

ployed between the anode and the cathode to control the intensity -of the electron current passing from the cathode to the anode. The path followed by the electrons is, however, not usually limited by any electrostatic or electromagnetic focussing action.

According to conventional practice cathode ray tubes are constructed with a cathode, grid, and anode similarin principle to those of a thermionic. valve, but the electrons are focussed into a'beam by the electrostatic fields produced by the grid and anode combined either with a further electrostatic field introduced by a second anode orvwith an electromagnetic field produced by a focussing coil outside the tube. This electron beam is brought to a point or'line focus on a screen which is usually fluorescent, and the electrons ultimately reach the anode from the screen. The electron image is made to oscillate across the screen in two directions, in most cases mutually at right angles by means of electrostatic deflection plates or electromagnetic coils.

With the present invention, use is made of certain features of the cathode ray type of discharge tube, in combination with an electrode arrangement by which amplification may be obtained without the necessity of resorting to intensity modulation of the electron beam. With the invention, the output from the tube is obtained by the use of an electron beam for periodically charging and discharging a target electrode which may constitute an output electrode.

In a preferred embodiment of the present inventfo'n the cathode consists preferably of along and comparatively narrow strip or wire, heated directly or indirectly so as to emit electrons. The grid and first anode consist of members with slots parallel to the length of the cathode, and focus the electrons into a beam of elongated A second anode or a magnetic focussing coil serves to focus the beam in to a line electron image on or near a target electrode which may be called for convenience the output anode. While this output electrode will be referred to as the anode, it does not carry the main current of the tube as in the conventional type of valve. The electrode is, however, the electrode from which the alternating output'from the tube can be obtained, and in this sense it may be conveniently referred to as'an anode. The output anode wholly or partially consists of or is coated with a substance of high secondary electron emissivity, and is connected to a terminal on the outside of the tube, The output anode is divided, mechanically or otherwise, into .electrically' connected parts or surface areas,

which may be'called respectively the positive and negative parts. When the electron image falls on the positive part secondary electrons are emitted, so that the potential of the output anode rises towards some upper limiting value which lies near to the potential of the finalanode of the electrostatic electrode system which produces the electron beam. The negative part of the anode is, however, so constructed or is associated with such additional means that, when the electron image falls thereon, the secondary electrons leaving the anode are less in number than the primary electrons reaching it, so that the potential of the output anode falls towards some lower limiting value which lies near the potential of the cathode. a

This division of the output anode into these two parts may be effected either by coating the negative part with a substance having a secondary emission coeflicient' less than unity over all the range of potentials over which it is employed, or by mounting an auxiliary electrode system near the said output anode, or by using an output anode of special shape, with or without'an auxiliary electrode system, so that electronsgfalling on one part of said output anode are trapped, and very few secondary electrons can escape. Two electrostatic deflection plates are provided the tube such that when a differenceof potential exists between them they deflect the electron image at right angles to its length.

When the electron image is deflected so as to lie mostly on the negative part of the output anode, electrons are forced on to said output anode so that its potential falls. When the electron image is deflected so as to lie mostly on the positive part of the output anode, secondary electrons are emitted so that the potential of the output anode rises. is made to oscillate from one part of the output anode to the other, an alternating potential is produced on the output anode. The amplitude of this alternating potential depends on the beam current of the electron beam, the frequency of the oscillations of the electron image, and the amplitude of the oscillation of the electron image. The maximum possible amplitude of the alternating potential is such that the potential varies between the two limiting values which the output anode can reach. If the alternating potential is not allowed to reach this maximum amplitude, then the amplitude is a direct linear function of the beam current, an inverse linear function of the frequency of oscillation of the electron image, and a direct but not necessarily linear function of the amplitude of oscillation of the electron image.

This valve is particularly suitable for amplifying weak voltage variations to form large variations of voltage with comparatively low current. It may, for example, be employed for amplifying the voltages produced by a microphone,

the amplified voltages being applied to the grid of the output valve of a P. A. amplifier.

To make clear the action 01. the valve therefore, its application to a problem of this type willnow be described in some detail, and with reference to the accompanying drawings, in which Figure 1 is a diagrammatic circuit of the valve and its associated components;

Figures 2a, 2b and 2c are diagrams of modifications of the anode assembly; and

Figure 3 is a diagram of a modified valve.

A valve J according to the present invention is shown diagrammatically in Figure 1, used in conjunction with one possible type of circuit whereby it is made to amplify signals of audio frequency. In Figure 1 audio frequency voltage variations of small amplitude from a .source A are to be amplified and the amplified signals are to be supplied to the grid E of the valve H, which valve may, for example, supply. a loudspeaker from its anode F. The D. C. potentials necessary to supply the valve J and the cathode and grid of the valve H are obtained from the potentiometer Q. The zero potential to which the other potentials are referred is taken for convenience as the potential of the cathode C of the valve J.

Referring now to the valve J, this valve comprises a cathode C and a grid G, which is biased to the negative potential necessary to give the beam current an appropriate intensity. The first anode B serves to draw electrons from the cathode C and to concentrate them in a narrow divergent beam. A: conductive coating U on the inside of the tube is connected to the anode B, and serves to maintain the interior of the tube at a constant electrostatic potential, thereby ensuring that the focus of the electron 'beam is undisturbed. An electromagnetic focusing system is included and consists of a coil M through which is passed an electric current to produce a magnetic field which focuses the electron beam into a line image at the output anode. The electron image does not necessarily lie parallel to the cathode as the magnetic field of the focussing coil causes rotation of the image, but for the sake of clarity Figure 1 is drawn as though the Lnage were parallel to the cathode. The output When the electron image anode is shown diagrammatically at XYZ. The form of output anode shown is one which is divided into the two parts mechanically, but also employs an auxiliary electrode system VW. All the parts XYZ of the output anode consist of or are coated with a substance of high secondary electron emission coefiicient. When the electron image falls on the parts Y or Z, secondary electrons are emitted from those parts and collected by the auxiliary electrode W, which is kept at first anode potential. If the electron image remains sufiiciently long on the members Y and Z, the potential of theoutput anode rises to a value near the potential of the electrode W, at which ipotential some of the secondary electrons return to the output anode instead of going to the electrode W so that equilibrium between the electrons reaching and those leaving the output anode is reached. The members Y and Z thus constitute the positive part of the output anode.

When the electron image falls on the member I X, the secondary electrons which are emitted are prevented from leaving the neighbourhood of the output anode by the electrostatic field produced by the auxiliary electrode V which is kept at a low potential, but somewhat positive with respect to the cathode; the reason for the small positive bias will be explained later. If the electron image remains sufliciently long on X, the potential of the output anode reaches a value near the potential of the auxiliary electrode V, at which potential equilibrium is again reached between the electrons reaching and those leaving the output anode. ,The member X thus constitutes the negative part of the output anode. The electron beam is focussed at the tip of the member Z, so that the'transition from one part to the other of the output anode is sharp.

It will be seen that the operation of the valve depends on the output anode always having a secondary electron emission coefficient greater than unity. Whatever substance is employed for the output anode, the secondary electron emission coeflicient falls below unity if the velocity of the primary electrons falls below some minimum value. Forflthis reason the primary electrons falling on the output anode must never have a velocity less than this minimum. This is secured by ensuring that the output anode has always a certain minimum positive potential relative to the cathode C. It is for this reason that the electrode V is given a positive bias potential as already described.

The electrodeW serves not only to collect secondary electrons liberated from the parts Y and Z of the output anode, but also to screen the body of the valve from the electrostatic fields produced by the'potentials of the electrode V and the output anode. This complete screening of the body of the valve from the potential of the output anode eliminates feed-back between the output anode and the input members of the valve.

A constant input carrier voltage variation of frequency higher than any frequency in the signal which requires amplification is generated .by th oscillator O and is applied to the deflection plates P3 and P4 of the tube, whose mean potential is kept at the potential of the first anode to avoid defocussing the electron beam. When the oscillating electron image is allowed to fall symmetrically on the output anode under these conditions, an alternating potential appears on the output anode, the frequency of this alternating potential being the same as the frequency of, the carrier voltage applied to the deflection plates. The production of this alternating potential involves the charging by the electron beam of the output capacity of the valve which is constituted by the output anode and members connected thereto. In Figure 1 this output capacity consists of the capacity of the output anode XYZ togetherwith the capacity S of the grid E of the valve H and the leads between the output anode XYZ and the grid E. To achieve this charging of the capacity the current intensity of the electron beam is so adjusted that, at the frequency of the applied voltage variations, the output capacity has just time to charge to the maximum potential necessary but no more. The value of the potential which is necessary will be defined below when modulation is considered. It now the electron image is deflected away from the symmetrical position, in the direction of, say, the negative part of the output anode, then the time for which the electron image lies on the positive part of the output anode is insufllcient to charge the output capacity fully. The amplitude of the voltage variation on the output anode which constitutes the carrier voltage is thus less. The output carrier voltage on the output anode may thus be modulated by deflecting the mean position of the electron image across the output anode. The mean position of the electron image is preferably so arranged that when the output carrier is unmodulated it has an amplitude of half the maximum amplitude which can be produced by the tube with the beam current intensity which is chosen. The signals to be amplified are applied to deflection plates of the tube which may be the same plates P3 P4 to which the input carrier oscillations'are applied, or which may be two additional plat-es Pl P2 the mean potential of which is also kept at anode potential, as shown in Figure 1, so as to deflect the mean position of the electron image across the output anode, thereby causing modulation of the output carrier signal proportional to the signals to be amplified.

In an alternative method of modulation, the mean position of the electron image when the output carrier is unmodulated is adjusted substantially to the position in which the rate of positive charging of the positive part of the output anode is equal to the rate of negative charging of the negative part. Modulation is efiected by modulating the input carrier voltage variation with the signals to be amplified. This modulates the oscillations of the electron image, and hence-modulates the output carrier, in proportio to the modulation of the input carrier without deflecting the mean position of the electron image.

The output signals produced on the output anode may be fed direct to the point where the signals are required, e. g. the grid of the next valve of the system in which the present valve is employed, which in Figure 1 is the grid E of the valve H.

Unless elaborate methods are adopted to control the wave form of the input carrier oscillation, the wave form of this high frequency oscillation is sinusoidal to a-close approxima-.

tion. It the size of the output anode on which is being amplified in the modulated carrier. Such distortion occurs to some extent in all conventional valve amplifiers, but for some purposes, e. g. audio amplification, it is important that it should be eliminated. It can be eliminated in the present system by employing a triangular or a saw tooth carrier deflection, but such a form of deflection is difllcult to produce at very high carrier frequencies, but more conveniently the distortion can be reduced to small proportions by using a carrier deflection considerably greater than the deflection produced by modulation. The amplitude of the output carrier signals must then be sufilcient to produce the required amplitude of modulation when modulation is applied. When this procedure is adopted the modulation of the output carrier will take effectover the substantially straight portion of the sinusoidal charging curve of the output carrier. and the distortion will be small.

According to an alternative method, the effect of the sinusoidal carrier deflection is compensated by using a metallic layer for the positive side of the output anode of such a shape that the area of the electron image in contact with the output anode varies with the deflection of the image. By choosing the shape of the output anode of the appropriat form, an undistorted ampliflcation can be obtained for any given shape of input carrier wave. Itmay be necessary to providean auxiliary collecting electrode, insulated from the main output anode, to collect electrons from the part of the image which does not fall on the main output anode.

Theoretically, correction by using an output anode of given shape permits the output carrier amplitude to be reduced to equality with the amplitude of the modulation to be applied to it, but a more reliable correction can be obtained if the amplitude somewhat exceeds this theoretical minimum. If a completely linear response is to be attained, account must also be taken of the 'change of secondary electron emission coefllcient of the output anode with change of incident velocity of the primary electrons reaching the output anode, i. e. with change of potential of the output anode. Allowance for this change of coeflicient of the secondary electron emission can be made by shaping the output'anode, or it may be taken into account, to advantage, when the other types. of correction are adopted.

Modulation need not necessarily be produced by applying both the carrier and the signal modulating the carrier onto the deflection plates. According to an alternative method the carrier is applied to a pair of deflection plates and its amplitude kept constant at all modulation levels. The-modulation of the carrier is achieved by applying the signals to be amplified on to a grid thereby changing the intensity of the beam. The amplitude distortion" considerations are then similar to those present in conventional valve technique. It should be pointed out that the output anode XYZ of the valve J is connected by a direct connection to the grid E of the valve H and that no grid leak resistance is used. This is made possible by the fact that the potentials of the cathode D and the grid E of the valve H are both determined by the potentiometer Q, the potential of the grid E being so determined via the anode XYZ of the valve J. These potentials can be so chosen that the grid E has the necessary, negative bias with respect to the cathode D.

The condensers Tl T2 T3 and T5, and the reslstances R2 and R4, constitute the supply and decoupling system for themains supply for the valve J.

An important and novel feature of the invention is that output signals oi! any desired amplitude can be obtained from input signals of any given amplitude within very wide limits, and the same valve can be adapted to suit diiferent input and output conditions by changing the steady value of the beam current and the electrode voltages. This statement and the limitations regarding amplification will now be explained in detail.

To any given value of the current intensity of the electron beam, there is, for any specified carrier frequency, some maximum amplitude ofoutput carrier which can be efiiciently obtained. This amplitude is obtained, when, if the carrier is fully modulated, the electron image oscillates from a position lying entirely on the positive part of the output anode to a position lying entirely on the negative part of the output anode. When a carrier of this maximum amplitude is developed, it is possible to modulate it with any "amplitude up to the same maximum amplitude. Thus, for

any given value of the current intensity of theelectron beam and specified carrier frequency there is a corresponding maximum value of the amplitude of modulation which can be produced in the output signals. In order to produce this maximum amplitude of modulation, the input signals-to be amplified must have a certain value. If the input signals have a smaller value, then, the output carrier will no longer be fully modulated, so a smaller amplitude of modulation will be produced in the output signals. The original value or the modulation of the output signals can, however, be restored if the beam current of the electron beam is increased. Thus by suitably adiusting the beam current, output signalsof any desired maximum amplitude can be obtained from input signals of any given maxi um amplitude within wide limits, the limitation ing the beam current intensity available in the electron beam. Such adjustment of the beam current may be effected by suitably adjusting the bias applied to the grid G (Figure 1). Another feature 01' the invention isthat the given maximum output amplitude can be chosen at any value, also within the limitations set by the maximumavailable current, by choosing the necessary voltages of the various electrodes correctly. Thus within the limitations mentioned, an output signal of any required voltage amplitude can be obtained from an input signal of any given voltage amplitude. The valve may thus be used to replace several stages of conventional thermionic valves. The maximum amplification obtainable from the valve is much greater than that obtainable from conventional thermionic valves. It is increased if the distance from the deflection plates to the output anode is increased, and in theory a valve of any required maximum amplification can be produced if this distance is made sufilciently large. I

The valve does not depend for the development or the output on the production of a fall of potential across a resistance and consequently a source of useless dissipation of energy which occurs in conventional audio-frequency thermionic valve amplifiers is eliminated.

In order to produce a sharply iocussed electron image, it is necessary to keep the current intensity of the beam producing that image reasonably low. If the current intensity of the electron beam requires, for the purpose for which the valve is being employed, to exceed the value for which a sharp electron image can be obtained, it is possible to divide the main electron beam into a number of component beams, e. g. by using a cathode in the form of a grid consisting of several parallel wires or strips, so that the current intensity of each component beam is sufliciently low. The electron image of this cathode will then be a series of parallel lines. The output anode must then also be constructed in the form of a grid containing a number of parallel elements equal to the num ber of parallel members constituting the cathode. Each member of the output anode must be similar to the whole output anode which would be employed in conjunction with asingle line cathode. Output anodes suitable for use in this way with a multiple cathode, are shown in Figures 2a and 217. Figure 2a shows an output anode differing in form from that shown in Figure 1. In the form shown in Figure 2a.,the

' aperture between the members Y and Z is small opposite to the member X, and hence most of the secondary electrons liberated from X are trapped in the space enclosed by X, Y and Z by the form of the electrode system. Consequently the electrode V may be omitted with only a slight change in theefliciency of the system, and in this case the output. anode is one where the division into two parts is effected by the shape of the output anode, as mentioned above. The form of output anode'shown m Figure 2b is the same as that shown in Figure I except in that it consists of a number of similar and mutually connected elements side by side, while that shown'in Figure 1 consists of onlyone such element. This arrangement alters the regions from which the secondary electrons are respectively collected and suppressed. The electrons are suppressed in the whole of the horizontal portions of the output anode, and in that part of the sloping members lying between the grid V and the horizontal portions, as shown at X in Figure 212, while the electrons are collected only from the'remainder of the sloping members, as shown at ZY. This v,

ondary emission coefiicient greater than unity at all such potentials. The electrode W collects secondary electrons emitted-from both parts.

If the valve is required'to amplify very low voltage variations, the distance between the deflection plates and the output anode necessary to produce the required sensitivity may become so large that the tube becomes inconveniently long; According to one feature oi. the present invention as shown in Figure 3 a magnetic field'or fields is provided to deflect the electron beam along a curved path. Conveniently solenoids may be provided to deflect the electron beam along a spiral path, the other electrodes being as previously described. The length of the tube may thus be substantially reduced. In suitable circumstances the magnetic field used to deflect the electron beam into a curved path may also serve to focus the beam, thereby avoiding the necessity of using the usual focussing system. To avoid distortions, as the electron beam passes along its spiral path, in the configurations of electrons which determine the final form of the electron image, and/or also to introduce the linear component of the spiral motion, appropriate electrostatic electrodes may alvantageously be employed at suitable points in the tube. The linear component of the spiral motion may alternatively be produced by tilting to the requisite extent the electrode system producing the electron beam.

What we claim and desire to secure by Letters Patent is:

1. An electronic valve device comprising a target electrode presenting two surface areas, means for producing an electron beam, defiection means for oscillating said electron beam to sweep symmetrically over alternation, means for superposing upon said oscillating electron beam an additional deflecting force to produce a non-symmetrical sweep of the electron beam with respect to said surface area, and means for restricting the resulting emission of secondary electrons from one of said surface areas with respect to that from the other surface area, whereby said target electrode is alternately charged and discharged.

2. An electronic amplifier comprising means including cathode and anode elements maintained at different direct current potentials for producing an electron beam, a target electrode to the control electrode of said second electronic valve device.

6. An electronic valve device comprising a target electrode presenting two surface areas, means for subjecting each of said surface areas alternately and symmetrically to the action of an electron beam, one of said surface areas comprising a substance having a secondary emission coefficient ,less than unity for potentials acquired by the target electrode and the other of said surface areas comprising a substance having a secondary emission coeificient greater than unity for such potentials, whereby one of said surface areas is charged in a negative sense 5 as a result of the action of the said beam and said surface areas in 2 isolated from said beam-producing means for direct current potentials said target electrode having two surface areas for'developing secondary electrons when said electron beam strikes thereon, means for directing said electron beam asymmetrically upon said surface areas in response to an impressed electric signal, and means including an auxiliary electrode adjacent said target electrode and maintained at a selected direct current potential with respect to the cathode of said beam-producing means selectively to determine different rates of escape of secondary electrons from the respective surface areas, whereby an alternating current potential is developed on said. target electrode in accordance with the varying distribution of the electron the two surface areas of the target electrode.

3. An electronic amplifier as recited in claim 2, wherein one of the surface areas of .said target electrode has a structural form that precludes the escape of secondary electrons from that surface area, and said auxiliary electrode is maintained at a direct current potential that promotes the flow of secondary electrons from the other surface area.

4. An electronic amplifier as recited in claim 2, in combination with a load circuit connected across said capacitive reactance, whereby the alternating current potential developed at said target electrode is impressed upon said load circuit.

5. An electronic amplifier as claimed in claim- 2, in combination with a load circuit including a second electronic valve device having a control electrode and a cathode, said target electrode being coupled directly to said control electrode,

and means for maintaining the cathode of the second electronic valve device at a direct current potential more positive than the lowest positive potential developed at said target electrode, whereby an appropriate bias is applied beam upon and between by capacitive reactance,

the other surface area is charged in a positive sense as a result of the action of the beam and the target electrode is thus alternately charged and discharged, and deflection means in said valve device for deflecting said electron beam into non-symmetry with respect to said surface areas of the target electrode.

' 7. An electronic valve device comprising a target electrode presenting two surface areas, electron beam producing means, electrode means for oscillating an electrom beam in such manner that each of said surface areas is subjected alternately and symmetrically to the electron beam, means whereby one of said surface areas is charged in a negative sense as action of the said beam, means whereby the other surface area is charged in a positive sense as a result of the action of the beam, so that the target electrode is thus alternately charged and discharged, and electrode means to which electric control signals can be applied to deflect the oscillating electron beam asymmetrical.- ly of said surface areas, thereby producing on the target electrode electric signal charges corresponding to said control signals.

8. An electronic valve device comprising a target electrode presenting two surface areas, electron beam producing means, electrostatic deflection plate means for oscillating the electron beam at high frequency and symmetrically to impact upon said surface areas alternately, means whereby one of said surface areas is charged in "a negative sense as a result of the action of said beam and the other surface area is charged in a positive sense as a result of the action of the beam, and means for deflecting the center of oscillation of said oscillating electron beam at the lower frequency of an electric signal to be amplified whereby said target electrode is alternately charged and discharged at the signal 5 frequency.

9. An electronic valve device comprising a target electrode presenting two surface areas, electron beam producing means, electrostatic defiection plate means for oscillating the produced electron beam symmetrically over said surface areas in alternation, means whereby one of said surface areas is charged in a negative sense as a result of the action of said beam and the other surface area is charged in a positive sense as a result of the action of the beam, whereby said target electrode is alternately charged and discharged, and further electrostatic deflection plate means for deflecting said oscillating electron beam under control of electric control signals, thereby producing electric signal charges on the target electrode in response to said control signals.

10. An electronic amplifier valve device comprising a target electrode presenting two sura result of the nected thereto to deflect the electron beam alternately and symmetrically to the two surface areas, impedance consisting substantially solely in capacitive reactance connected between said target electrode and said cathode, means selectively controlling the rate of escape of secondary electrons from the respective surface areas, whereby one of said surface areas, is charged in a negative sense as a result of the action of said beam and the other surface area is charged in a positive sense as a result of the action of the beam, thereby to establish an al-'- ternating current potential on said target electrode, .t

11. An electronic valve device comprising a target electrode presenting two surface areas,' electron beam producing means, electrode means for controlling an lectronbeam in such manner that. each of said surface areas is subjected alternately to the predominant action of an electron beam, means including capacitive reactance between said targetelectrode and said electron. beam producing means whereby one of said surface areas is charged in a negative sense as a result of the action of the said beam, means in cluding said capacitive reactance and an auxiliary electrode whereby the other surface 'area is charged in a positive sense as a result of the action of the beam so that the target electrode is thus alternately charged and discharged, and means serving to screen the electron beam producing means and the said control electrode means from the target electrode to eliminate thereby feed-back between the various electrodes.

12. An electronic valve apparatus comprising a target electrode'presenting twp surface areas, means for subjecting each of said surface areas alternately to the predominant action of an electron beam, means whereby one of said surface areas is charged in a negative sense as a result of the action of the said beam, means whereby the other surface area is charged in a positive sense as a result of the action of the beam, so that the target electrode is thus ,alternately charged and discharged, and means for producing a magnetic field to deflect the electron beam along a curved path whereby the advantage of anelectron beam of long length is obtained without increasing the length of the/envelope enclosing the electrode system of the device.

13. An electronic valve apparatus comprising a target electrode presenting two surface areas, means for subjecting each of said surface areas alternately to the predominant action of an electron beam, means whereby one of said surface areas is charged in a negative sense as a result of the action of the said beam, means whereby the other surface area is charged in a positive sense as a result of the action of the beam, so that the target electrode is thus alternately charged and discharged, and means for producing a magnetic field to cause the electron beam to traverse a spiral path whereby the advantage of an electron beam of long length can be obtained without increasing the length of the envelope enclosing the electrode system of the device.

14. A system for amplifying electric wave signals and incorporating the electronic valve device as claimed in claim 7, comprising means for applying carrier wave signals to the first electrode means of said device to thereby obtain thedesired predominant action of an electron beam on the two surface areas alternately, and

means for applying the electric wave signals "to the other electrode means of the said device to produce thereby on the target electrode of said device electric signal charges corresponding to the said electric wave signals.

15. A system for amplifying electric wave signals and in corporating the electronic .valve device as claimed in claim 9, comprising means for applying carrier wave signals to the first mentioned electrostatic deflection plate means, and means for applying such electric wave signals to the said further electrostatic deflection plate means, to thereby produce on the t rget electrode electric signal charges corresponding to the said electric wave signals, said carrier wave signals having a frequency wh'ch is constant and higher than the frequency of the electric wave signals to be amplified. 1

16. A system for amplifying electric wave signals and, incorporating an' electronic valve device as claimed as claim 2, wherein means is provided to adjust the amplitude of electric signal charges produced on the target electrode in response to the application of the electric wave signals to the device, said means comprising means for adjusting the potential of said auxiliary electrode means to a desired value and level relative to cathode potential of the beam producing means.

17. A system for amplifying electric wave signals and incorporating an electronic valve device as claimed in claim 2, wherein said means for determining the rates of escape of secondary electrons from said surface areas includes a screening electrode, and means for adjusting the direct current potential of said screening electrode with respect to the beam producing means thereby to establish the lowest possible potential of the target electrode relative to cathode potential.

MARCUS JAMES GODDARD. PAUL NAGY.

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