US1986397A - Space discharge tube having a negative resistance characteristic - Google Patents

Description

Jan. 1, 1935. A HUND 1,986,397

SPACE DISCHARGE TUBE HAVING A NEGATIVE RESISTANCE CHARACTERISTIC Filed April 5, 1932 OUTPUT INVENTOR August Hullll Patented Jan. 1, 1935 1,986,397

SPACE DISHABGE TUBE HAVING A NEGA- TIVE RESISTANCE CHARACTERISTIC August Hand, West Orange, N. 1., assignor to Wired Radio, Inc New York, N. Y., a corporation of Delaware Application April 5, 1932, Serial No. 603,284-

2 Claims. (Cl. 250-36) This invention relates to electrical discharge understood from the following description and tubes and more particularly to gaseous tubes in by reference to the accompanying drawing in which upon setting up a glow discharge therein which:

a negative resistance characteristic is exhibited. Fig. 1 depicts one form of an electrical dis- 5- An object of my invention is to provide an charge tube having two electrodes in an ioniz- 5 electrical discharge tube of this character coming circuit and two other electrodes in an oscilprising a plurality of electrodes surrounded by lator circuit which exhibits a negative resistance a gas at an attenuated pressure, two of which characteristic; electrodes may be characterized as ionization Fig. 2 is a modification of the tubes of my electrodes while at least one additional electrode invention showing only three electrodes of suit- 10 is included in a work" circuit, the voltage of able formation, one of which, namely the cylinwhich may be adjusted independently of the drical electrode, serves a double purpose beionizing voltage. cause it is comprehended in the two circuits for V Another object of my invention is to provide ionization and for the oscillatory output respeca tube of the class described which functions tively; and 15 so as to exhibit a negative resistance character- Fig. 3 is another modification of my invention istic, thereby rendering it useful in a variety of showing electrodes of suitable formation to act difierent circuits such as, for example, in an as an amplifier having a negative resistance oscillator or an amplifier. characteristic.

Another object of my invention is to provide The discharge tubes of thisv invention are 20 a tube of the class described in which the eleccapable of modification in many respects. The trodes are of suitable formation and so arranged relative sizes and shapes of the electrodes as with respect to one another that the optimum well as the kind and pressure of gas in which conditions may be obtained for exhibiting the they are enveloped may be varied within wide negative resistance characteristic of such a tube. limits in order to obtain the desired results. 5

In my copending application Serial No. 573,076 The essential feature, however, is the presence filed November 5, 1931, the theory of operation of a very pronounced negative resistance charof gaseous discharge tubes to exhibit a negative acteristic in the tube itself. It has been shown resistance characteristic was expounded in dethat with this negative resistance characteristic tail. In that application, however, tubes having the tube functions very satisfactorily either as an 30 only two electrodes were shown. oscillator or as an amplifier.

In my cope di pp ca on Se O- 0,561 In the herein described embodiments of my fi d February 1932 I ve described gaseous invention I use at least three, and, in some cases, discharge tubes having a p a y of a least preferably, a greater number of electrodes. The

four electrodes. In that applic I h voltage required for ionization and the voltage 35 mentioned the fact that under certain condiapplied i the work circuit may be adjusted inticns such tubes y b t a e a ve edependently of one another. Furthermore, the sistance characteristic- The exhibition of a protective resistance which is necessary in the negative resistance characteristic is ionization circuit and which is undesirable in the ever relied upon for Producing the desirable work circuit can be so disposed as to render the results for which the several species of invention tube highly emcient in its operation shown in Serial 590 561 are intended.

Referring now to Fig. 1, a four-element tube Thismvention may, therefore, be distinguished is she n and in c0 nection there ,ith for zggii gi g f i g gg fg al g gm trative purposes, an oscillator network appears. particulars. g pp g Outwardly the tube may be of conventional type By means of the separate ionizing electrodes havmg f" a 1; an envelope prongs as herein described it is possible to produce a The ionization cathode 4 and iomzation anode 5 degree of ionization h t t undesirable are placed in a circuit which includes the source laxation variations may be avoided in the work of potential 6 and the Protective resistance 50 circuit and the negative resistance reaction pro- The w k upon whic Osc o y be duced in the latter can be extended over a much generated l s n nod 8 an a y in wider working range than would be possible, cathode 9, the latter preferably surrounding all say, with tubes having only two electrodes. of the other electrodes. Each of the electrodes These and other advantages will be more fully is supported by an insulated post, preferably of 55 glass, in order that ionization may not take place between the leads.

A suitable difference of potential may be applied between the anode 8 and cathode 9 by means of a battery 10 which is isolated from the oscillatory currents generated in the network, use being made of one or more choke coils 11. A resistance 12 may also be used to adjust the voltage across the electrodes 8 and 9. In shunt with the work electrodes 8 and 9 is an oscillator network comprising an adjustable condenser 13 in parallel with the primary inductance of a transformer 14, this parallel combination being in series with a condenser 15. The condenser serves to prevent a flow of direct current from the battery 10 through the primary coil of the transformer 14.

The operation of this oscillator system is as follows: Oscillations will be set up in a wellknown manner in the shunt branch when a negative resistance action takes place between the electrodes 8 and 9. This is due to the fact that the negative resistance permits power to be subplied to the condenser with a periodicity depending upon the charge and discharge rate of the condenser 13 in association with the transformer 14 as shown. In order to suitably adjust all of the factors entering into the operation of this oscillator system it will be understood that any desired frequency may be obtained upon adjustment of the elements 13, 14 and 15 with respect to the values of the negative resistance. The limiting values of the latter are determined by choosing a suitable current in the work circuit, which in turn is derived from the selection of a proper voltage of the source 10 and the adjustment of the tap along the resistance 12.

Referring now to Fig. 2, another oscillator circuit is shown in connection with a modified form of the tube of my invention. This tube comprises an electrode 9a which serves the double purpose of an anode in the ionizing circuit and a cathode in the workcircuit. This electrode is preferably of cylindrical or cup-shaped formation. The ionizing circuit includes the source of potential 6, a choke coil 16, the electrodes 9a and 4 and the protective resistance 7. The oscillatornetwork of Fig. 2 differs from that of Fig. l chiefly as regards the arrangement of the adjustable condenser 17 which is placed in series with the primary of the output transformer 14. The necessity for an additional condenser such as condenser 15 in Fig. l is thereby avoided. The source of potential 10a is connected on the negative side through the choke coil 16 to the electrode 9a. Another choke coil 18, and, if desired, a resistance 12 i1. series therewith may be connected between the positive pole of the battery 10a and the work anode 8.

From what has been said with regard to the operation of the tube of Fig. 1 as an oscillator the corresponding manner of operation of the tube and network of Fig.2 will be readily understood by those skilled in the art.

Referring now to Fig. 3, another modification of my invention is shown comprising a threeelement tube. The ionizing electrodes of this tube comprise preferably a small solid cylindrical anode 19 and a surrounding cathode 9b of hollow cylindrical formation. The latter electrode also acts in cooperation with the tip shaped anode 8 to produce a negative resistance reaction in the work circuit.

The tube of Fig. 3 may be used as an amplifier but this use will be understood to be merely illustrative of a variety of purposes to which it is adapted. The electrodes may also be varied somewhat in their structure.

In order that suitable potentials may be applied between the several electrodes, I find it convenient to use a potentiometer 20, to the negative end of which the electrode 91) may be connected. The ionizing circuit for this tube includes the source of potential 21, the protective resistance 7, the ionizing anode 19, and electrode 9b, which in this circuit acts as a cathode and which is connected to the negative side of the source 21. Between the work circuit anode 8 and the electrode 9b may be connected an amplifier network including the secondary of an input transformer 22 in series with which is an ordinary resistance 24 and a condenser 25.

The output of this network is derived from differences of potential across the resistance 24. Since the latter is in series with the negative resistance of the tube and since amplified variations are produced across the resistance 24 with respect to the input voltage generated in trans-' former 22 it will be seen that a favorable degree of amplification takes place in the output branch 23. The negative resistance action in this case is the same as was explained in my copending application Serial 573,076.

If desired, the amplifier network may be readily modified by those skilled in the art so as to obtain a current amplification as distinguished from voltage amplification.

The output branch 23 includes a condenser 27 for preventing the flow of direct current therethrough. The condenser 25 bypasses the useful variable current around the resistance of the potentiometer 20. The proper voltage may thus be applied to the electrodes 8 and 9b through the adjustable tap 26 on the potentiometer without offering too great an impedance in the potentiometer to the variable currents.

In carrying out my invention it will be understood that a wide degree of variation in the construction of the tubes is permissible. A particular tube which I have tested was found to give satisfactory results and to produce a negative resistance that could be varied from about 1000 ohms to about 100,000 ohms. This tube happened to be filled with helium to a pressure of about 15 mm. Argon is particularly suitable for negative resistance work. I have used other gases, however, and with pressures as great as 150 mm. The ionizing current of the tube that was tested was about 20 milliamperes while the work circuit current was in the neighborhood of 6 milliamperes. The voltage-was taken from a battery eliminator, about 500 volts being applied in the ionizing branch and about 150 volts were impressed on the work circuit. Stability of operation was obtained by proper adjustment of the values of the protective resistance 7 and the adjustment of the potentiometer 20 or the resistance 12. The values herein stated for the tube under test are not in any way to be considered as important or critical. Neither do I wish to limit myself to the three species of my invention herein illustrated. It will be under-- stood that a wide variety of modifications of tubes exhibiting a negative resistance characteristic is possible. My invention, therefore, is limited only in accordance with the scope of the appended claims.

I claim:

1. In a space discharge tube system comprising, an envelope having an attenuated gaseous atmospherethereinandapluralityoielectrodes, means including certain of said electrodes for producing therebetween a region of electrical stressiorcausingacorrespondingregionoiprimary gaseous ionization between said meansinciudingcertainoisaidelectrodesior producing therebetween another region of electrical stress for causing between said electrodes a secondary region of gaseous ionisation, one 0! said electrodes being iormed to substantially enclou said primary and secondary regions 0! ionization in order that said region of ionization may exert a contro eflect upon said secondary ionization whereby a pronounced negative resistance characteristic is exhibited by said tube and relaxation oscillations are avoided.

2. In a space discharge tube system including. an envelope enclosing an attenuated gaseous atmosphere and a plurality of electrodes, means torcausingcertainotsaidelecia-odestoproduce betweensaidelectrodesaregionoielectrical producethcrebetweena -1 esion oi primary ionimtion. said means includmln malw maryionizationcircuithavsasourceoivoltageandatherein andmeans for causing certain otsaid elec. trodes to produce therebetween another region oielectricalstresstosetupa slon of ionization between said electrodes, said meansincludingaworkcircuithavingasouroe said secondary ionization to produce a negative for said tube and inhibit the generation 01' relaxation oscillations.

AUGUST HUND.

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