US2002238A - Negative resistance - Google Patents

Description

May 2l, '1935- v E. H. YoNKERs, JR 2,002,238

` NEGATIVE RESLSTANCE Filed Jury 22, 195o l l s l l l i Patented May-*21, 1935 UNITED STAT-s PATENT'. oFFlcE 2.002.238 f g l NEGATIVE na'srs'ranca adware n. :minima` Jr.,carimo, m. -iippucauon Julyfzz, i930, semi Naseem somma. (ci. 25ms) 'I'he present invention relates in general to electrical circuits, particularly those of the type known as negative resistance'circuits for producing oscillating currents, the present inventiony 5 employing a function of the electrons thrown oil from an incandescent cathode for this purpose.

One of the objects ofy my invention is to provide a device having negative electrical resistance characteristics, that is, a device wherein the current varies inversely with the applied potentlal, and'- wherein this variation ofcurrent is attained by regulation of the velocity of flow of. elewctrons between the various electrodes of the Priorart devices --known to me wherein nega-A phenomena is employedfor essential. to, the attainment of the functions of this device.

Further objects of this invention reside in the provision of a unitary structure capable of convenientinstallation in electrical circuits for producing the desired results, and for carrying out the method here involved; the provision of a system and method of producing electrical oscillations vreferred to whe'rein the various electrodes of the device are appropriately mounted in a highlyl evacuated -container conveniently yof transparent material, suchasglass or the like, and provided with suitable lead-in wires capable of connectionas desired in the circuit in which the device is to be used.

The foregoingand such anna-.objects and advantages which may appear or be pointed out as this description proceedmare attained in a structural embodiment ofl the invention for carrying 40" the method and system vinto eiiect, illustrated in the accompanyinggdrawing wherein: y

Figure 1 is a composite view in longitudinal and transverse section illustrating one form( of a device for carryingL out the invention; j

Figure 2 is a diagram illustrating the current characteristics oi one of the devices otthis invention; f

Figure 3 is a diagrammaticRview of an electrical vcircuit incorporating the featuresof this invention. l

Referring now'more particularly t9 th drawing and ilrst to Figure 1, I have illustrated a highly evacuated envelope i, which may be formed of a transparent material, such k,as glass, and includes the enlargedibulb portion I, pro- .REISSUED vided wimrsduced ends 1 and s. formed with uiwardly directed axially aligned pedestals l and 9a, which serve as supporting elementsforthe' lead-in wires and electrodes hereinafter described. .l

Extending through and `supported by the pedestal 9 I provide a illamentary cathode III, whose lead-in conductors II are connected so as to supply current for heating the cathode I0 to incandescence. In the structural embodiment shown in Figure 1 for convenience I provide a -grid I2, which latter ismounted preferably on the longitudinal axis of the device and is helical inV form, that is, is formed of a coiled wire with the convolutions thereof slightly spaced apart. The grid is supported on its conductorwire Il, which latter extends through the pedestal 9a and is connected in an electrical circuit as will be hereinafter described.

The grid |27 is itself surrounded by a system of electrodes including the inner electrode I4 composed of the disks I5, which are thus perpendicular to the axis of the grid. The electrode Il is provided with the collar I6 surrounding and supported by the pedestal 9, a lead-in wire Il being connected to said collar.

A fourth electrode is provided which comprises an annular plate I8, supported by arms I! ilxediy secured to a ring 20 surrounding and supported by the pedestal 8a. A lead-in wire 2I is connected to the ring 20. It will be understood that the electrode I8 isin the natureof acylinder whose axis is coincident with the axis of the device.

The operating characteristics oi the device are determined by the geometry of the disc system or third electrode. The envelope 5 should be exhausted to such a degree of vacuum that no appreciable current is carried by gaseous ions when the required potentials are -applied to the device.

If the cathode I0 is connected to earth and heated to incandescence and a positive potential is applied to the grid I2 there will be a iiow of l electrons from cathode Ilto grid I2. Some of these electrons will pass through the openings in the coiled portion or the grid and move toward the plates I5 of the third electrode Il.V Thelr velocity `upon reaching the boundaries of the third electrode will be determined by the potential ot that electrode with respect to the cathode. Thus, a stream of electrons will flow between the dises I! of the third electrode with a velocity determined by the potential of said electrode. v

, Due to their mutual repulsion the electrons comprising this stream develop an additional u ing a negative current of electricity to flow from the third electrode I4. The magnitude of this current is an inverse function of the velocity of the stream of electrons -which enters the space be-A tween the discs I5 of the third electrode provided the fourth electrode VI8 is maintained` at some suitable positive potential. This is because at high velocities the time required for the individual electrons to pass between the discs is small and their displacement vtward the discs is therefore small, whereas, at low velocities their'time between the discs is sufficiently long to permit a. large portion of them to migrate to the discs. Thus, when the potential of the third electrode is h ighthe current to it is small and the current to the fourth electrode is large and when the potential of the third electrode is low the current to it is large and that to the fourth electrode is small.

These characteristics can best be understood by reference to the curves shown in Figure 2 in which the ordinates represent electron currents to the third and fourth electrodes I4 and I8 and the absciss represent the potential of the third electrode I4. Curve A represents the current-po- -tential characteristic of the third electrode and curve B ,represents the, corresponding variations in current to the fourth electrode when the potential of the third electrode is varied, the potential of the fourth electrode being fixed at some suitable positive value. The portion of the curves between the limits R and S indicates the useful or operating range of the device. Between these limits the slope of the current-potential characteristic of the third electrode is negative and the slope of the corresponding current characteristic of the fourth electrode is positive but equal. in value to that of the third electrode. Thus, the third electrode provides negative'resistance and the fourth electrode provides a source of current variations equal in amplitude to variations which occur in the circuit of thethird electrode without appreciably loading said circuit.

In Figure 3 I have illustrated a system in which a negative resistance device such as I have described above may be used to generate alternating currents of any desired frequency from a source of direct current. The electron discharge device 5 is constructed as shown in Figure 1. l A battery l22 provides current for heating the lamentary cathode Il) and a battery 23 is employed to impress a constant positive potential upon'the grid I2.

'I'he fourth electrode I8 is also connected to battery 23 through the primary winding 25 of a transformer 26. The'secondary winding .21 of said transformer is included in some work circuit such as the antenna 28 of a radio transmitting system.

The circuit connecting the third electrode I4 to the cathode .I 0 includesal suitable portion of battery 23 and a resonant circuit consisting of inductance 29, capacitance 30.and resistance 3|.

The point 31 at which the thirdelectrode is connected to battery 23 is so selected that the positive potential impressed upon the electrode I4 lies within the operating range of the device, that is,

between the limits It and S shown in Figure 2.

of the current-potential characteristic, is less than the equivalent parallel resistancel of the resonant circuit, oscillations or pulsating currents will be generatedin this circuit. Current variations 0f similar amplitude occur ln the circuit which includes electrode I8 as described above and thus supply energy in the form of alternating currents to the work circuit.

The frequency of the oscillations generated is determined entirely by the constants of the resonant circuit which is associated with the third electrode. Variations in-the nature of the work circuit have very little eifect upon the generated frequency.

Since my' device depends for its operation only upon the geometry of theelectrodes comprising it and upon the fundamental properties of an' electron stream, its characteristics can be varied to meet the requirements of specific applications by properly designing the form of the third elec' trode. In this respect my device offers distinct advantages over previously employed negative resistance devices based upon gas ionization or secondary emission effects, which have been found to be somewhat erratic in their operation and critical as to operating'potentials.V

Having thus described my invention and illusing a highly evacuated receptacle, an electron emitting cathode therein, a grid'adjacent to said cathode, said cathode and grid being connected to a source of difference potential, a third eleotrode in said receptacle comprising spaced plates lying adjacent to the path of electron emission from said cathode, said third electrode being connected through a resonant circuit to a portion of said source of diilerence of potential 'so as to be at positive potential with respect to said cathode, and a fourth electrode in said receptacle connected to a portion of said source of potential of greater .positive potential than that impressed n said third electrode and forming part of an external work circuit, electrons emitted from said cathode passing between the plates of lsaid third electrode intheir path to the fourth electrode, whereby the current ow between said electrodes is varied inversely with the velocity of the electrons.

- 2. In a device of the character described, in combination, av thermionic device comprising a highly evacuated envelop, an electron emitting cathode-in said envelop, a grid adjacent to said cathode, and an anode in said envelop, a negative resistance element interposed between the grid and said anode and comprising a plurality of substantially parallel inter-connected spaced metal plates lying parallel to the electron streamfrom saidcathode to said anode, and'means for im` the work` Q

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