US2107811A - Amplifier tube - Google Patents

Description

Feb. 8, 1938. E. H. YONKERS, JR

AMPL IFIER TUBE Filed Deo. 5. 1930 O CONTROL ELEMENT mTENT'lAL.'

lThis invention relates in n amplification apparatus and more particularly to Patented Feb. s, 193eY .*'vagUNITl-:D .STATES PATENT OFFICE 2,107,811 AMPLIFIER TUBE Edward H. Yonkers, Jr., Chicago, Ill. Application December 5, 1930, serial No. 500,217

2 Claims.

general to electrical that type of apparatus adapted to be employed in the amplifica-tion of high frequency electric currents especially as employed in radio frequency circuits, and the invention includes apparatus for amplifying more especially the high frequency ,j alternating currents of a transmitting or receiving circuit, though it will be understoodthat theinvention is capable of employment for other purposes, and, therefore, finds a Wide field of f utility.

VThe principal object ofr this invention is to aso-called three element Yprovide'amplification of alternating high fre- 5,

quency electric currents by the provision of'an improved method of arranging the electrodes f gas-free vacuum tube and to accomplish the desired results without the objectionable tor the cathode, therefore, ,eliminating the undefeed back" from the anode sirable effectsof inter-electrode' capacitance.r

More specifically, when a current is carried Vthrough gas-free space by ions all of the same sign, the potential gradient between the cathode ,and anode through the space containing the ions is not linear but assumes a curvature deter- K mined bythe distribution and density of space- A Vcharge* (as expressed by Poissons equation). `Y.Under vpractical operating conditions, electrons 'beingemitted from the cathode with finite velocities and the space-chargeiitself limiting rthe magnitude of the current, this curvature is such that there is a point of zero potential between VYtheranode and cathode and a reversal of sign of the electrostatic eld'at this point so'that the slope of theV potential gradient at the cathode Ais negative.

Y' `'in thisV negative field betweenthe cathode and r ifromfthe cathode alone determines the the density and distribution of space-'charge so changes that the point'ofzero potential between 4cathode and anode moves towardthe the point ofzero potential in the space-charge is electrost'atically shielded from the anode. lIf the potential of the lanode is from" zero tothe saturation point where the rate of emission of electrons current,

cathode ,becoming coincident withit at the saturation value1 ofV current.

element andcathode be 'approximately equi- Thus, aA control element'or grid placedV in Figures 1 and 2 herein.

gradually increasedv value, that is, theV n The Yslopeof the. potentialvv `#gradient at the ca hode becomes zero at this point.` It is desirable, therefore,that the control (Cl. Z50-27.5)

throughout the maximum useful variation in anode potential.

Theforegoing andsuch other objects and advantages as may appear or are pointed out as this description proceeds are in the structural embodiment of the invention illustrated in the accompanying drawing, in which:

Figure l is a longitudinal sectional View of the amplifying apparatus including the improvements of my invention. l0

Figure 2 is a transverse section view taken on the line 2-2 ofY Figure 1 looking in the directionindicated by the arrows.

Figure 3 is a diagram curve characteristic of the device of this invention,

Figure 4 illustrates one circuit arrangement in which the devicemay be incorporated.

Figure V5 is a view similar to Figure 1 of an alternative form of the device.

The method of amplifying high frequency alternating electric currents of this invention includes the steps of bringing an electron emitting element to a state of incandescence in order or to form a cloud of electrons or negative ions or space charge. This forms the cathode of Vthe ,amplifying device and as is well known to those skilled in the art, the negative electrostatic field being thus generated adjacent to the cathode limits the magnitude of the current. A control element is placed within the space charge so that in the normal range of operation of the device, it is always locatedV in the negative electrostatic field of the space charge. This space charge will thereby serve to shield the control element and prevent feed back between the anode and the control element. c

vOne structure forrcarrying out this method, and which structure may be considered as a preferred form for some purposes, is illustrated A-I provide a highly evacuated envelop 5 formed of a dielectric material such as glass, the yenvelop being free'of any modifying or controlling gas, this being accomplished in the conventional manner.

The envelop isv preferably madev elongated in Yshape and atoneend is provided with a pedestal plied to the anode iii this equilibrium is 2 energized to an incandescent state in the usual manner by imposing a suitable potential on the conductors 8 and id. It is to be observed that the helical filament is thus disposed substantially along the longitudinal axis of the envelop or tube 5.

The control element is formed of a helical conductor i2, whose convolutions are slightly smaller in diameter than those of the filament l and disposed in alternative relationship throughout as to always be in the space charge generated by the lament l. Thecontrol element l2 has its opposite endsaixed as at i3 and ifi to a lead-in conductor l5 at the opposite end of the tube. Of course, the co-nductor l5 may pass out through the pedestal 6, but for convenience the mounting and supporting structure shown in Figure l is to be preferred. In order to shield the conductor l5 from the anode `I provide a tubular conductor il connected to the cathode through conductor l@ and engaging the pedestal I6 for tending to make the structure less sensitive to vibration due to extraneous shocks or jars.

The anode comprises the cylindrical metallic element iB supported by bracket wires le, carried by a collar 2i) which surrounds the pedestal 6 and is xedly secured thereto. The anode i8 is thus supported adjacent to the locality of the filament l in spaced relationship thereto so as to receive the stream conducting electrons which are thrown of from the incandescent lament.

Under practical operating conditions the electrons are emitted from the cathode 'i with iinite velocities and the space charge located immediately adjacent to the iilament, in View of the positioning of the electrodes and potential impressed, serves to limit the magnitude of the current and to produce a potential gradient between the anode and cathode of such curvature that there is a point of Zero potential between the anode l 8 and the cathode 'l and a reversal of sign of the electrostatic eld at this point. Thus the slope of the potential gradient at the cathode is negative. lt is desirable that the control element be placed back of the cathode 1 or immediately adjacent thereto so that it will always be located in the negative iield created by the space charge.V

Thus it will be seen that when this control element or grid is placed in the negative field between the cathode and the point of zero potential in the space charge, the control element is shielded from potential variations of the anode iii occurring in the normal operation of the device.

As hereinabove pointed out when the potential of the anode is gradually increased from zero to the saturation value of current, the density of the space charge and its 'distribution will change so that the point of zero potential between the cathode and the anode moves toward the cathode and becomes coincident with it at the saturation point. For this reason it is desirable that the control element and cathode be approximately equi-distant from the anode so that the shielding effect will be present throughout the maximum range of operation.

When the cathode 'l is brought to incandescence, the released electrons move into the space rsurrounding the filament and thus form a space charge which eventually prevents further elec trons from leaving the iilament, that is, the number of electrons returning to the lament becomes equal to the number leaving it. When a constant positive potential 0i a value less than that required to produce the saturation current is apdisturbed the purpose oi" Y due to the migration ofthe electrons to the anode and it follows that a new equilibrium will be established in which the number of electrons leaving the lament becomes greater than the number returning to it. rlhus, a current flows betweeny the anode and the cathode which is limited by the space charge potential by virtue of its power to cause some of the emitted electrons to return to the iilament. rihus the volume of the current passing through the device may be controlled by applying various potentials to the control element i2 for the reason that these potentials affect the electrostatic field surrounding the filament and change the magnitude and distribution of the controlling space-charge. Due to the positioning of the control element adjacent to the filament I produce a greater change in current per unit change in its potential than that produced by the same change in potential of the anode and this condition must prevail in order for the def vice to function as an amplifier.

Figure 3 illustrates a typical current characteristic curve oi the apparatus of my invention. The ordinates 2l represent anode currents and the abscissae 22 represent control element potentials, .i

indicated at 23, consisting of a primary winding 2li and a secondary winding 25 of a transformer T and the output side of the circuit is indicated at 2b and comprises the primary winding 21 and a secondary winding A28 of the transformer T.

The amplifying circuit contains the device 5a of this invention in which the lament or electron emitting element is shown at la energized 'by a suitable source of current 29, and a cathode is shown at @il immediately adjacent to the filament la, an anode or plate being indicated at 3|. The source of electric potential such as a battery 32 is also arranged in the amplifying circuit.

The terminals of the primary of the transformer T are connected to a'source of current to be amplified and one of the terminals of the secondary 25 is connected by a conductor 33 to the control element til, the other conductor being connected to the negative side of the battery 29, this battery providing current for heating the lament 'Ea through the leads and iii. The positive side of the battery 2S is connected to the negative side of the battery 32 andthe positive side of the later is connected bij/.conductor 34 to one side of the primary winding 2l of the transformer T. The plate, or anode 3 l, is connected by conductor 35i to the opposite end of the primary 21. The secondary 28 ci the transformer T provides an output circuit for the amplified currents.

Potential variations impressed upon the control element 3@ through the transformer T cause amu pliiied current variations to occur in the anode circuit including the battery 32 and primary winding 2l and thus, through the transformer T energy is transferred to the output circuit.

Beca-use of the shielding Yeffect 0i the space charge on the control'element, the circuit shown in Figure 4 will function as a suitable amplier and will not generate oscillating currents within it'seh". This condition has been found to obtain with the constants of the circuit designed to 2,107,811 `amplify alternating currents at frequencies as high as 15 mega-cycles per second.

The form of the invention shown in the Figures 1 and 2 is more particularly adapted for employment where uni-directional electric current is employed for heating the filament.

Referring now to Figure 5, an alternative form of the invention shown in Figures 1 and 2 more particularly is disclosed herein. A highly evacuated envelop 5d is provided having a pedestal 69 extending axially thereof. The end of the envelop or tube 5d adjacent to the pedestal is exl ternally provided with a base for the external terminals of the tube, a suitable adhesive matter "H, such as plaster of Paris, or the like, being applied for aflixing the base 10 to the tube 5d in Y' the conventional manner.

In this form of the invention I provide lead-in conductors 12 and 13 connected to thepins 14 and 15, respectively, said lead-in conductors being connected at their inner ends to the terminals of the double spiral filament 16 which forms the electron emitting device. The lament is supported by an axiallyextending rod 'I1 embedded atl in thehead of the pedestal 69 and a suitable metallicv cap or disc l!)` shields the upper end of the control element 80 from the anode. VVWithin the filament I provide a control element 80 in the form of a cylindrical metal tube, this tube being supported by a support rod 8| embedded in the khead of the pedestal 69 and additionally by a lead-in Wire 82 which extends through the pedestal and connects to the terminal pin 8 3.

In order to shield the lead-in Wires and associated elements from the anode, I provide a cylinsubstanially coincident,

drical shielding member 84 connected to the cathode as at 92 and carried by the pedestal 69 and provided with a closing partition or cap 85, apertured at 86 to accommodate the lament and control element which project therethrough.

The anode is indicated at 81 and is a cylindrical plate supported by straps 88 from a ring 89, such ring being applied ixedly to an auxiliary pedestal 90 formed at the opposite end of the tube.- The anode is connected to the output side of the amplifying circuit by the lead-in conductor 9| connected at 92 to one of the straps 88.

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

1. An electron-discharge device for amplifying pulsating currents comprising a helical electronemitting cathode and a helical control element of the same pitch as the said cathode the convolutions'whereof are interpositioned and a cylindrical anode of larger 4diameter than the said cathode, the axes o-f the three elements, being said control element being located between the cathode and the point of zero potential in the surrounding space charge so that the cathode is electrostatically shielded from the anode.

2. An electron-discharge device for amplifying pulsating currents, comprising a helical elecronemitting cathode and a helical control element of the same pitch as the said cathode, the convolutions whereof are interpositioned and a cylindrical anode of larger diameter than said cathode, the axes of the three elements being substantially coincident.

EDWARD H. YONKERS, JR.

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