USRE20446E - Negative resistance - Google Patents

Description

July 13, 1937.

E. H. YONKERS, JR NEGATIVE RESISTANCE Original Filed July 22, 1930 POTENTIAL OF 774mb ELECTRODE Reissued July 13, 1937 Re,

UNITED STATES PATENT OFFICE NEGATIVE RESISTANCE Edward H. Yonkers, Jn, Chicago, 111.

Original No. 2,002,238, dated May 21, 1935, Serial No. 469,809, July 22, 1930. Application for reissue October 18, 1935, Serial No. 45,617

7 Claims. (Cl. 250-36) This invention relates in general to electrical justed to meet the requirements of various apcircuits, particularly those of the type known plications. as negative resistance circuits for the production Further objects of this invention reside in the of oscillating currents, the present invention em- D on O a t y Structure Capable of ploying a function of the electrons thrown ofi venient installation in electrical circuits for pro- 5 from an incandescent cathode for this purpose. d t des d s, d for Ca y Out One of the objects of my invention i t r the method here involved; the provision of a vide a device having negative electrical resist- System a method o p o u electrical ance characteristics, ordinar r sistanc i cillations referred to wherein the various elec- 10 erally considered as positive resistance, that is, trodes f he device r pp o b' m n 10 the current flowing in a positive resistance varies in a highly evacuated Container Conveniently f directly with the potential applied to it. Anegan p n material, such as glass r the lik tive resistance, on the other hand, is one in which and p vide Wi h bl l -in Wir s p bIe the current varies inversely with the a lied of connection as desired in the circuit in which potential. the device is to be used. 15

Prior art devices known to me wherein nega Th foregoing an suc o her bje ts nd adtive resistance characteristics are present depend vantages which y pp be p te t either upon gas ionization or upon th phenomeas this description proceeds, may be attained in non known as secondary emission of electrons a structural embodiment of the invention for o9 for their operation, as distinguished from my carrying the met od d y e l present invention wherein neither of these phetrated in the accomp y drawing her nomena is employed, or essential to, the attain- Figure 1 is a ud a S t n taken On ment of the functions of thi device, the line |l of Figure 1a and illustrates one Negative resistance is capable of cancelling an form of the device for carrying out the invention.

equal positive resistance, and hence, when it is Figure la is a transverse section taken on the connected to a resonant circuit having positive line Iala of Figure l. resistance, it is capable of cancelling the positive Figure 2 is diagram l r i h ur n resistance and causing sustained oscillations to C a te s o One f the dev ces of this inoccur in the resonant circuit. A device having vention;

a negative resistance characteristic of suitable Figure 3 is a diagrammatic View Of an 8180- 30 Value is useful as a means for generating electrical circuit incorporating the features of this trical oscillations. invention.

It is obvious from this that one of the objects Referring now e particularly o the awof my invention is to supply a negative resisting a d fir o Figure I ave i lus ated a 3.3 ance device which may be designed to supply highly evacuated envelope 5, which may be various negative resistance values useful in the formed of a transparent material, such'as glass, situations mentioned above, among many others. and includes the enlarged bulb pertien 6, p These adjustments and regulations in accordvided with reduced ends 1 and 3, formed with ance with my invention are calculable in advance i wa y d e d axially aligned P ta s 9 and 4c and so may be incorporated in the finished device 9a, whi h se v as pp r l s f r th 40 to meet the performance demands required. A lead-in wires and electrodes hereinafter deother object of my invention is to provide a scribeddevice wherein the current varies inversely with Extending through and Supported y e Dedthe applied potential and wherein this variation estal 9 I provide a filamentary t de ll Whose y of current is attained by regulation of the velead-in conductors II are connected so as to locity of flow of electrons between the various Supp y Current r the heating f t e athode electrodes of the system. A further object of H] to incandescence. In the structural embodimy invention is to produce a true negative rement as shown in Figure 1, for convenience I sistance which may be designed to produce va- P v de a grid Which latter is mounted D e rious values of negative resistance over a wide erabli 0n t e o tud al axis of the device range'and not subject to the accidental pheand is helical in form, that is, is formed of a nomena which act within a relatively limited coiled wire with the convolutions thereof slightly range to produce negative resistance which canspaced apart. The grid is supported on its connot be wholly or satisfactorily controlled or adductor wire l3, which latter extends through the 55 pedestal 9a, and is connected in an electrical circuit as will be hereinafter described.

The cathode it! and the grid I2 are surrounded by a system of electrodes including the inner electrode I4 composed of the discs 55, which are thus perpendicular to the axis of the grid. The electrode I4 is provided with the collar I6 surrounding and supported by the pedestal 9, a lead-in wire I! being connected to said collar.

A fourth electrode is provided, which comprises an annular plate I8, supported by arms IS fixedly secured to a ring 2%] surrounding and supported by the pedestal 9a A lead-in wire 2| is connected to the ring 29. It will be understood that the electrode I8 is in the nature of a cylinder whose axis is coincident with the axis of the device and substantially at right angles to the plates or discs I5.

The envelope 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 Ii! is connected to earth and heated to incandescence a positive potential is applied to the grid i2 and there will be a flow of electrons from the cathode Ii] to the grid I2. Some of these electrons will pass through the openings of the grid and move or flow in a stream substantially parallel and between the plates 55 of the electrode E4. Their velocity upon reaching the zone between the plates I5 of the electrode M will be determined by the potential of that electrode with respect to the cathode. Thus, the stream of electrons will flow between the surfaces of the discs 55 at a velocity determined by the potential of said electrode. If the potential of the electrode is low, the electrons will move slowly and will be greatly influenced by their mutual repulsion, that is, they will spread toward the surfaces I5 so that practically all of the electrons will be received upon the surfaces of electrode I4. On the other hand, if the potential is high, the velocity of the electrons will be high, and the time required for their passage between the discs will be relatively short, hence they will have very little opportunity to spread. Consequently, most of them will pass through in their flow and reach the anode I8.

It is the mutual repulsion of the electrons, since they all possess a definite negative charge, together with curvature of the electrostatic lines of force which terminate at the inner edges of the discs I5 which cause the electrons to spread towards the surfaces of the discs. The magnitude of this spreading and consequently the magnitude of the current received by the electrode I4 is an inverse function of the component of velocity, parallel to the surfaces of the discs, which the electrons possess by virtue of the positive potential app-lied to the electrode I4 with respect to the cathode.

Thus, the current received by electrode I4 varies inversely with the potential applied to it and it is obvious from the nature of this process that form of the resulting negative resistance characteristic as well as its operating range, from the quantitative standpoint, depend entirely upon the size and space relations of the conducting surfaces which comprise the electrode I4.

This is a highly important feature of the in- Vention since, because of I this condition, it is possible for the first time, to control the value of a negative resistance as well as its operating limits and, thus, to design this highly useful electrical factor to meet the various requirements of its many applications.

As described above, it is clear that the operation of the device depends upon the action of electrode I4 upon an electron stream which is directed toward it, and into the extended channels formed by the spaced plates I5 which comprise it. It is also clear that in order for the device to be operative the volume of this electron stream or the number of electrons flowing per unit time from its source at the cathode must be substantially constant over the working range of the device. Obviously if the rate of fiow of electrons from the source increased as the potential of the electrode I4 increased, additional electrons would be received by the discs I5, and if this increase were equal to or greater than the decrease in the number of electrons received by the discs due to the action described above, the desired inverse characteristic would be entirely cancelled.

The desired constant current electron stream may be obtained by several methods. For example, in the expression of the invention shown in Figure 1, I have employed the grid I2 placed close to the electron emitting cathode and maintained at a constant positive potential. The value of this potential determines the rate of flow of electrons through the openings of the grid I2 and in this manner a relatively constant flow or stream of electrons is caused to flow toward the electrode I4.

Thus, as the potential of electrode I4 is varied over its working range this fixed or constant current is divided between electrodes I4 and I8 in accordance with the desired operation of the device.

This is clearly shown in Figure 2 in which the curve A represents the portion of the current which is received by electrode I4 and curve B that which passes through the openings of electrode I4 and is received by the anode I8 over the working range of the device indicated by R and S. It will be seen that the total current or the sum of the currents on the A and B curves for all potentials between R and S is substantially constant. This condition of constant total current is necessary to the proper operation of the device and is what is meant by the terms constant volume electron stream, and saturated, or constant current source of electron.

It has already been pointed out that the magnitude of the current of electricity flowing from the electrode I4 is an inverse function of the velocity of the stream of electrons which enters the space between the discs or surfaces I5 of the electrode I4 provided the anode I8 is maintained at some suitable positive potential. This is, as has also been pointed out, because at high velocities the time required for the individual electrons to pass be-' tween the discs is small and their displacement toward 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 electrode I4 is high the current to it is small, and the current to the anode I8 is large, and when the potential of the electrode I4 is low the current to it is large and that to the anode I8 is small.

These characteristics can best be understood by again referring to the curves shown in Figure 2 in which the ordinates represent electron currents to the electrode I4 and anode I8 and the abscissae represent the potential of electrode I4. Curve A represents the current-potential characteristic of the electrode I4 and curve B represents the corresponding variations in current to the anode I8 when the potential of the electrode I4 alone is varied, the potential of the anode I8 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 electrode I4 is negative and the slope of the corresponding current'characteristic of the anode I8 is positive but substantially equal in value to that of the electrode I4; Thus, the electrode I4 provides negative resistance and the anode I8 provides a source of current variations equal in amplitude to variations which occur in the circuit of the electrode I4 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. A battery 22 provides current for heating the filamentary cathode I0, and a battery 23 is employed to impress a constant positive potential upon the grid I2. The anode I3 is also connected to battery 23 through the primary winding 25 of a transformer 26. The secondary winding 2'! of said transformer is included in some work circuit such as the antenna 28 of a radio transmitting system.

The circuit connecting the electrode I4 to the cathode I0 includes a suitable portion of battery 23 and a resonant circuit consisting of inductance 29, capacitance 3|], and resistance 3|. The point 31 at which the electrode I4 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 R and S shown in Figure 2. If the value of the negative resistance in the circuit of electrode I4, as determined by the slope of its current-potential characteristic, is less than the equivalent parallel resistance of the resonant circuit, oscillations or pulsating currents will be generated in this circuit. Current, variations of similar amplitude occur in the circuit which includes anode I8 as described above and thus, energy is supplied in the form of alternating currents to the work circuits.

The frequency of the oscillations generated is determined entirely by the constants of the resonant circuit which is associated with the electrode I4. Variations in the nature of the work circuit have very little effect upon the generated frequency.

Since my device depends for its operation only upon the geometry of the electrodes 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 electrode I4. In this respect my device ofiers 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.

Having thus described my invention and illustrated its use, what I claim as new and desire to secure by Letters Patent is:

1. In a device for producing alternating currents, in combination, a valving device comprising 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 of potential, an electrode in said receptacle comprising spaced plates lying adjacent to the path of electron emission from said cathode, said electrode being connected through a resonant circuit to a portion of said source of difference of potential so as to be at positive potential with respect to said cathode, and an anode in said receptacle connected to a portion of said source of potential of greater positive potential than that impressed on said electrode and forming part of an external work circuit, electrons emitted from said cathode passing between the plates of said electrode in their path to the anode, whereby the current flow between said electrode and cathode is varied inversely with the velocity of the electrons.

2. In a device of the character described, in combination, a 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 stream from said cathode to said anode, and means for impressing positive potentials on said grid, anode and element with respect to said cathode such that the portion of the electron stream intercepted by said parallel plates varies inversely with the potential applied thereto over the working range of the device.

3. A negative resistance device comprising a constant source of electrons, an anode, and an electrode comprising a plurality of inter-connected, spaced, conducting plates extending between cathode and anode in and substantially parallel to the stream of electrons which flows from the cathode toward the anode, said anode and electrode being connected to sources of positive potential with respect to the cathode such that the current received by the electrode increases and decreases inversely with the potential applied to the said electrode over the working range of the device.

4. A negative resistance device comprising a constant current source of electrons, an anode, and an electrode interposed therebetween consisting of a plurality of conducting surfaces extending in a direction which is substantially parallel to the flow of electrons from the source to the anode, all enclosed in a highly evacuated envelope, said electrode and anode being connected to sources of positive potential with respect to the said source of electrons, such that the portion of the electron flow intercepted by the said electrode varies inversely with the potential applied thereto over the working range of the device.

5. A negative resistance device comprising a constant volume source of electrons, an electrode comprising a plurality of inter-connected, spaced, conducting plates the surfaces of which extend between the cathode and anode in a direction which is substantially parallel to the path of electrons moving from cathode to anode, said electrode and anode being connected to sources of positive potential with respect to the cathode such that the portion of the electron flow received by the electrode increases and decreases inversely with the potential applied thereto over the working range of the device.

6. A negative resistance device, an electron emitting cathode, means for maintaining the electron emission from the said cathode at a substantially constant value over the working range of the device, an anode and a negative resistance element comprising a plurality of interconnected, spaced, conducting plates the surfaces of which extend between the said cathode and anode in a direction which is substantially parallel to the electron flow from cathode to anode, all enclosed in a highly evacuated envelop, and means for applying positive potentials to said element and anode with respect to the cathode, such that the portion of the electron flow intercepted by the said element varies inversely with the potential applied thereto over the working range of the device.

7. In a device for producing alternating currents, in combination, a valving device comprising a highly evacuated envelope, a constant source of electrons, an anode and a negative resistance element interposed between said source and said anode and comprising a plurality of interconnected, spaced, conducting plates the surfaces of which lie substantially parallel to the flow of electrons from the source to the anode, said negative resistance electrode being connected through a resonant circuit to a source of potential which is positive with respect to the electron emitting cathode and a work circuit being connected between the anode and its source of potential which is also positive with respect to the cathode, such that the oscillations generated in the circuit associated with the negative resistance element cause current variations to occur in the work circuit associated with the anode.

EDWARD H. YONKERS, JR.

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