US1630753A - Amplifier - Google Patents

Description

May 31,1927 1,630,753 1 J. MASSOLLE ET AL AMPLIFIER Filed April 4. 1921 2 Sheets-Sheet 2 Patented May 31, 19 27; i

UNITED STATES PATENT OFFICE.

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Application fled April ,4, 1921, Serial No. 45am, an in Germany December a, 1919. Gunman mu m rnovxsrons or an Aer or .iuac'n a, 1921, 41 arm. a, ma.

Amplifiers with several amplifying stages tained within a single tube the wiring conare known in which each stage includes a nections being omitted; an 1 special or separate cathode. The stages are Fig. is a wiring diagram of the ampliusually independent of each other and an adfier shown in Fig. 4, the connections for twoditional amplifier is utilized for adding each stages only being indicated to prevent conamplifying .stage. \Vhen several stages are fusion. obtained from one tube the tube would be In the construction shown in Figs. 1 to 2 correspondingly large on account of numerinclusive, the cathode is is shown as arranged ous cathodes employed. If an'exact adjustin the middle of the tube. At opposite sides ment of the cathode temperatures is to be thereof, grids g and g are positioned with made possible, the cathodes must be heated anodes a and a respective1y,grids g and separately. It is indeed'also known to ar- 9' being interposed between anode a and range the cathodes one behind the other, the cathode, and the anode a and the cathode connectedin series, and to heat them in comrespectively. The current to be amplified'is la mon. But with a given heating current the considered as flowing through the primary temperature of an incandescent wire is to of transformer T, the secondary of which is a very great extent dependent upon the heat connectedlto cathode is and the first grid 9 emitted by the filament by radiation and producing the potential drop across the conduction. Consequently it is very diificult space betweengrid g and cathode k, which 2 with this arrangement to obtain approxipotential drop is indicated on the drawings mately equal temperatures of the'cathodes as eg'. .This' input potential causes an amwith the same heating current. plified current to flow in the first anode or An object of the invention is to provide plate circuit includinganode a and cathode an amplifier in which several amplifying k. This serves to correspondingly increase 2 steps may be'accomplished in a single tube, the potential drop between the grid 9 of the having a single cathode and a plurality of second amplifying stag'e,and cathode is, and anodes and grids. this correspondingly produces greater varia- Other objects consist in the provision of tions of resistance and current between the the improved combinations of arts and do anode a of the second stage and the tails of construction, all as will more fully cathode is. set forth hereafter and be particularly The coupling of the two-stages of amplipointed out in the appended claims. fication may be eifected in anyknown man- In order that the inventihn may be more nor. In Figs. 1 to 2" inclusive, a resistance clearly understood attention is hereby dicoupling is shown and in Fig. 3 an inductive 35 rected to the accompanying drawings illus-- coupling. trating diagrammatically various forms of The variations of current thus produced in construction, by way of example, which are the anode circuit of the first stage are, in the included within the invention. Y a caseof inductive coupling (Fig. 3), trans- In the drawings, Figure '1 represents a 'mlttedf in a known manner by the transtwo-stage amplifier'fwith both stages conformer T to the second-amplification stage tained within a sin le tube. with a resistance as increased variations of potential eg be coupling between tie stages; Figure 1" is a tween the cathode and grid 9 The varying modification thereof; l a potential on grid 9 causes an amplified cur- Figs. 2 and 2 are further modifications rent to flow in the second anode circuit which, 45. thereof; as shown, includes a useful resistance'N, the Fig. 3 is a similar two-stage modification output circuit being considered as led-off haging a transformer coupling between the from the terminals of this resistance, 'In this 1 stages; e arrangement bothanode circuits can be sup- Fig. 4 is a cross section taken through a plied from a single constant source of poto four-stage amplifier, all the stages being contenti l- E, included in the "common portion of the two anode circuits. This same source mayfas shown, be used to supply the heating current for the cathode, through the circuit indicated, including the resistance shown at H. In this figure also a small re sistance w is shown'as inserted between battery E and the cathode, the potential drop through this resistance'being used to obtain a negative bias at the ids.

Considering now a tu havlng resistance coupling between the two stages as shown in ig. 1, the'arrangement of the cathode, anodes and grids is the same as has been described. A heating circuit for the cathode is shown as extendin through connection 1 and separate heating atteryrE.

The first anode circuit extends from anode a, by conductor 2 to battery E and resistance 'wp shunting the same, and then through the coupling resistance '10 to cathode is. This resistance w is suitably of the order of values of the average internal anodecathode resistance of the first amplifying step. Variations of the input potential drop eg' cause,-because of variations of resistance between a and k, variations of the distribution of otential drop in the first anode circuit, as etween the Internal path a'-lc and the external resistance which may be considered as resistance '11); The potential variations across resistance w are transferred to the grid 9 and are effective as potential variations between this grid and cathode is as indicated at eg. The connections from the terminals of the resistance '11) to cathode la and grid 9 are shown in Fig. 1" as conductors 3 and 4. The second anode circuit is shown in Fig. l as includin the separate source E and the resistance across the terminals of which the output circuit of the tube may be connected.

In the connection shown by Figs. 1 and .1 on the one hand and Figs. 2 and 2 on theother hand, there is a difierence, namely, that the potentials transmitted to grid 9 are negative in the first case and are positive in the second case. In both cases the potentials impressed on grid 9 are comparatively lar e because of the high anode potentialswhic are used on account of the internal properties of the tubes. That is to say, resistance couplings are used between the sta es of amplification; the anode potentials are igh in comparison with anode potentials which would be used with transformer couplings. It will, therefore, often be necessary to diminish the average potentials impressed upon grid g.

This can, for example, be eflected by the insertion of an auxiliary potential e, with this potential being of'a sign which is opposed to that of the drop of potential across 7 the terminals of the couphn resistance with which it is connected, (F igs. 1 and 2).

Potential eg, impressed on grid 9, is then.

always equal to the drop of potential 0 across the coupling resistance wless potential e. In the arrangement shown in Fig. 1, there is an advantage in that the battery- E can be divided by a sliding contact} on resistance wp, the dro of potential from the upper terminal 0 resistance wp, as shown in Fig. l, to the sliding contact being the drop of potential e referred to. As noted, a separate source of otential E is required for the second ano e circuit.

The variations of current in thelrs 'econd anode circuit are reversed in direction in comparison with those of thefirst anode circuit, and, accordingly, the internal resistance of the two stages ca -7c and a -lc, connected in parallel with the source E would work counter to each other, if both anode circuits were simultaneously fed from source E Therefore, there would be smaller potential drop variations across the resistance w and across the path c e k of the tube because of this counter action of the two anodecathode pathsy-and, accordin ly, the variations of current-in the secon anode circuit would likewise be correspondin 1y smaller.

In the connection shown by Fig. 2, this disadvantage does not arise with a common source of anode potential, since resistance to is no longer in the common portion of the anodecurrent circuits, and the resistance 40 'whose voltage dro is utilized for the production of a suitable bias at grid 9 has so little resistance that its voltage drop is negligible. This connection also permits the heating of the cathode from the battery E. In Fig. 2, a separate source of potential as is shown as connected in the conductor extending to grid 9 this source having its terminals connected oppositelytc' those of the source E, with which it is connected in series with the resistance 10'.

In the connections shown b Figs. 1 and 2", the condenser C is substituted for the auxiliar potential e This condenser. C, if well insulated possesses a practically infinite resistance ior direct current, but with a smaller resistance for alternating current, which depends on its capacity and on the frequency of the current. The average voltage 0 com rises in part a direct current voltage which is distributed in accordance with the ohmic resistance of the path traversed, while the other component of voltage 42 comprises an alternating potential which is distributed in accordance with thealternatin current resistance of condenser C and t e path 9 -10 of the tube. In order to obtain definite roportions for the direct current voltage (lEStIlblltlOD, ohmic resistances w and w are connected up in arallel to condenser C and thepath g -lc, igs. 1 and 2", resistances w and to being preferably balanceda These resistances 'w and w are, of course, properly chosen for the poptrodes N, h

neso'pss tential drop required across the same. A suitable bias can then be placed on girdg by abonnection from the terminal of resistance as, through resistance w, to grid 9 The resistance to provides a shunt around condenser C for carrying'the direct current. component to the voltage which is to be carried to grid g The number of amplifying steps with a common cathode is not limited to two. In Figs. 4 and 5 a form of construction is shown with four amplifying steps, this construction being suitable for connection with re sistance coupling. It will be noted that in such a case the increase of the grid potential. from one step to the-next does not depend upon the absolute strength of current in the different anode circuits, but upon the relative current variations in the anode circuits. Accordingly, comparatively small anodes may be used in the first three amplifying steps, with, however, a larger anode in the fourth amplifying step, since the variations of potential are here to' be converted into variations of output current.

' In the construction indicated in Fig. 4, a common cathode k is shown at the center of the tube with three small anodes, a a and a each shown as surrounded by a tubular grid g, g and g, respectively. A larger anode, a, is shown, as semi-circular in cross section, on the opposite-side of cathode is with its grid g of semi-circular section interposed between the cathode and anode a.

Protecting grid shaped auxiliary electrodes h, k and h are shown as surrounding grids g, g and g respectively, while a similar protecting electrode h, semi-cylin-' drica-l, is shown as interposed between cathode is and grid 9. These protecting elech and h are provided for the purpose of preventing interaction" between the various amplif ing stages of the tube, that is, these auxi iary electrodes serve to diminish the passage of lines of force from one amplifying step to an adjacent amplify ing step. Suitable constant potentials are impressed upon grids h, if, 71. and 72. which potentials may be either positive or negative, as desired. The use of such protecting electrodes is illustrated only in Figs. 4 and 5, but. they may be used in the constructions illustrated inthe other figures as well, although, of course, there is not so much need for the same when two step amplification only is used. Protection against this action can be obtained by separating the grids of the difierent stepsa suflicient distancefrom each other, but this cannot be practically accomplished when, say, three or four amplifying steps are mounted in a single tube without having a tube of undesirable large size, and accordingly the rotection by means of the auxiliary electro es h, h,- h and h is deemed preferable. The various "electrodes used may be of desired forms, such for example as the concentric arrangement indicated in Fig. 4, the invention, however, not being limited in this respect. It may also be noted in Fig. 4 that the cathode is is represented as larger in cross section than in Figsyl to 3 inclusive, this for the reason that the lines of force leading from the cathode to the various anodes in Fig. 4 will be reduced by the protecting electrodes [L -k and accordingly this loss transformer coupling, T, which connects to grid 9 and to cathode is. The anode circuit of the first stage extends from anode a through resistance '20 battery E and resistance 'w to cathode This provides. the

varying potential drop across the coupling resistance w, which impresses a. corresponding varying potential across the space be tween cathode k and the grid of the next am lifying stage which is represented as gri g, the connection to grid 9* extending through the counter-acting source of otential e as described above. -The an eci'rcuit for the second stage illustrated, extends from anode a? through resistance N and battery E back to the cathode is. The protecting electrodes k and k are illustrated as connected together in series and through an auxiliary batter eh, which impresses the desired potentia on electrodes b and 71?, back to cathode in. It will be understood that the connections for the amplifying steps involving anodes a and a and grids g and 9 have been omitted for simplicity and the connections shown in Fig. 5, as if electrodes a and g were in the next amplifying step to electrodesa and 9 If the connections for all of the steps were indicated, those which. have been met described duplicated What we claim is:

1. A multiple-stage amplifier, comprising a single evacuated container, a single integral undivided heated cathode, common, as a whole, to the several stages of am lification, and a plurality of anodes and grids in said container, spaced away from the cathode and from each other, and all'arran ed outside the would be entire cathode, connections or im ressing an input lprostential difierence across t e cathode and t grid, external circmts connecting each anode with the cathode, and means for couplin the anode-cathode external C11- cuit of eac sta 0 except the last with the cathode and grit? of the next stage.

2. A multiple-stage amplifier, comprising a single evacuated container, a single undivided heated cathode, common, as a whole, to the several stages of amplification, and two anodes and two grids, in said container,

spaced away from the cathode and from each other and all a-rran (1 outside the entire cathode, connections or impressing an input potential difference across the cathode and rst grid, an external circuit connecting the first-stageianode with the cathode, means for impressmg drop of potential in said circuit across the cathode and grid of, the second stage, and an external circuit connecting the second stage anode with said cathode.

3. A multiple-stage amplifier, comprising a single evacuated container, a single undivided heated cathode, common, asa whole, to the several stages of amplification, andtwo anodes and two grids in said container, spaced away from the cathode and from each other and all arranged outside the entire cathode, connections for impressin an input potential difference-across the cat ode and first grid, an external circuit connectin the first-stage anode with the cathode, sai. circuit including a resistance, means for transferring-drop of potential in said resistance across the cathode and grid of the second stage, and an external circuit connecting the second stage with said cathode. Y

4. A multiple-stage amplifier, comprising a single evacuated container, a single integral undivided heated cathode,: common as a whole, to the several stages otampli cation, and a plurality of anodes and grids in said container, separated by vaouous space from the cathode and all arranged outside the entire cathode, said cathode hem of uniform cross-sectional area throng out,

connections for impressing an input oten tial difference across the cathode an first grid, an output circuit connected to the cathode and last anode, external conductive circuits connecting each anode with the oathode, means for impressing direct current po'-' tential upon each of said circuits, and means for transferring potential variations in each anode-cathode circuit except the last to the grid of the next stage.

5. A multiple-stage amplifier, comprisin a single cathode common .to the severa stages of amplification, a plurality of anodes and grids in said container, connections for impressing an input potential difference across the cathode and first grid, circuits connecting each anode with the cathode, means for transferring potential variations in each anode-cathode circuit to the grid of the next stage, auxiliary screening electrodes interposed between said grids and cathode, and means for impressing a constant potential upon said screening electrodes.

6. A multiple-stage amplifier, comprisin a single evacuated container, a cathode and a plurality of anodes and grids therein, connections between said electrodes for produc ing a plurality of amplification stages-within the tube with electron-discharge paths between the cathode and the several anodes, and means, comprising screening electrodes, for reducing reaction between the electrondischarge paths of the several stages.

7. As a new article of manufacture, a multiple-stage amplifier, comprising a single evacuated container, a centrally positioned cathode, and a plurality of anodes with grids surrounding the same, and screening electrodes surrounding said grids, all spaced from said cathode, all within said container.

8. As a new article of manufacture, a multiple-stage amplifier, comprising a single evacuated container, a centrally positioned cathode, a plurality of anodes of comparatively small size withgrids surrounding the same, on one side of the cathode, a lar er anode of semi-cylindrical section, on anot er side of the cathode, with a grid interposed between the same and said cathode, all within said container.

In testimony tures.

JOSEPH MASSOLLE. HANS VOGT. DR. J OSEF ENGL.

whereof we afiix our signaas

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