US2262916A - Electric amplifying system - Google Patents

Description

Nov. 18, 1941.

H. BOUCKE ELECTRIC AMPLIFYING SYSTEM 3 sheets-sheet 1 Filed April 26, 1959 FIG-6 FIG-5 INVENTOR,

HEI N z Bouc KE FIG? ATTORNEY.

Nov.; 18, 1941. K H. BoUcKF.

ELECTRIC MPLIFYING SYSTEM Filed April 26, 1959 3 Sheets-Sheet 2 AAAAlAAAL .R ma Nm E WU 1o a z m E .H

ATTORNEY.

Nov. 18, 1941. H. BoUcKE 2,262,915

ELECTRIC AMPLIFYING' SYSTEM Filed April 26, 1939 3 Sheets-Sheet 3 INVENTOR.

ATTORNEY.

AAAAAA HEINZ BOLJCKE I l L.,

#Awww n :nx

Patented Nov. 18, 1941 2,262,916 ELECTRIC AMPLIFYING SYSTEM Heinz Boucke, Berlin-Charlottenburg, Germany,

assignor to Radio Patents Corporation, a corporation of New York i Application April 26, 1939, Serial No. 270,053 In Germany May 30, 1938 16 Claims.

Thelpresent invention relates to electron valve' amplifiers and a method of operating the same, more particularly to aperiodic or direct coupled multi-stage amplifiers for translating or amplifying signals comprising a substantial frequency band or for amplifying relatively slow periodic or aperiodic variations of electric current or potential. There are numerous applications for amplifiers of this type such as in industrial control equipment, telegraphic signalling, measuring systems, in radio receivers and various other uses.

An object of the invention is the provision of a direct coupled electron valve amplifier comprising two or more amplifying stages embodied in a single amplifying Valve.

Another object is the provision of a novel automatic volume control (A. V. C.) arrangement for use in radio receivers or the like characteriZed by substantially increased sensitivity and efficiency compared with A. V. C, systems at present known in the art.

A more specific object is to provide a self-regulating amplifier or volume limiting device adapted to automatically maintain a desired output level in a radio receiverr or any other amplifying system.

' Another object is to provide a multi-grid electron valve amplifier capable of simultaneously amplifying both direct and alternating currents.

`With the above objects in view, the invention contemplates lthe use of a multi-grid electron valve amplifier having an input contro1 grid upon which are impressed the potential variations to be amplified to cause corresponding fluctuations of the electron stream passing through the valve. Amplified potential variations are derived from the first positive or anode grid `and impressed through a direct current coupling arrangement upon a second control grid arranged to control the same electron stream. Suitable compensating means are provided to suppress the effect of the positive operating potential at the anode grid upon the second control grid and to maintain the latter at a suitable preferably negatively biased operating point to ensure efficient and faithful amplification and Itranslation of the input potential variations within a desired operating range. Further direct coupled stages may be included in the same valve for additionally controlling the common electron stream. The final amplified potential or current is derived from an anode and/or one of the positive grid electrodes.

The above and further objects and aspects of the invention will become more apparent from 55 the potentiometer resistancey 2'0.

vthe applied input potential.

the following detailed description taken .with refei'ence to the accompanying drawings illustrating several practical embodiments of the invention and wherein:

Figures 1 to 7 representsimple direct coupled two-stage amplifier circuits embodying a multigrid electron valve in accordance with the invention,

l Figures 8 and `9 illustrate circuits yembodying a multi-grid valve providing more than two amplifying stages,

Figure 10 lillustrates an lamplifier stage of a radio receiver or the like embodying the improvements of the invention for automatically controlling the output volume oi 'the receiver,

Figure 11 shows an amplier stage in a radio receiver 'or the like embodying the improvements of the invention for suppressing inter-carrier noises during the tuning of the receiver,

Figures 12 and 13 are graphs illustrative of the function'and novel. effect `obtained by the invention,

Figure 14 .illustrates the invention as embodied in a radio receiver for obtaining improved automaticvolume control.

Similar reference numerals identify similar parts ythroughout the different views' of the drawings.

yReferring to the drawings, Figure 1 shows a simple direct coupled amplifier constructed -in` accordance with the invention and comprising a multi-grid valve Ihaving a cathode I-I which may be of either the directly or indirectly heated type, aninput control grid I2, a first' positively biased or anode grid I3, in theexample shown' having the form of a space Vcharge grid located nearv the vcatl'iode,` a second preferably negatively biased control` grid` I4 and an anode I5. The input voltage to be amplified is impressed between the cathode I I and input grid I2 through terminals a, b the latter being shunted byl an input impedance such as an ohmic resistance I8. The positive or anode grid I3 is connected to the positive vterminal of a high tension supply source 'represented by the potentiometer resistance I9 through ai load impedance 2| whereby amplified potential variations will be developed at the grid I3 corresponding to the variations of- These potential variations are'impressed directly and conductively upon the control grid I'lI through a potential divider resistance 22 connected between the grid I3 and the negative terminal `of a compensating battery or potential source represented by The positive tive operating point to ensure most favorable' operating conditions and efficient amplification' of the electron current variations. The ampli.-

iied current variations may serve'fftd operate a" measuring instrument 23 if the system serves for measuring purposes, or alternatively, the instru# ment 23 may bereplaced by ay suitable Acoupling impedance or network -for applying theHampli-` ed current or potential variations to a suitable translating device or to a further amplifying f In-the aforeldescribed 'arrangement the electron discharge current passing through the valve from the cathode to the yanode is subjected to the simultaneous..control'y by the 'two gridsV I3 and..|4 f i. 11. l. I

:Figure 2 showsa two-stage direct coupled am` plifler similar to Figure 1 wherein a special vcom-l pensatingsource is dispensedwithVA by the provision of a resistance 25 in series with'the-cathode lead or ground of the valve. Theeffectof vthis resistance is to render the. control grid I4 negative relative to .the cathode thereby. c'ompensat` ingtheefect ofthe positive or vanode potentialk asa. result ofthe conductive connectionv bet-Ween the. :grids I3 and I4.. This kind .of compensation shown in the embodiment Figure 5 being otherwise similar to Figure 4. Alternatively; the screen grid may be omitted or separate screens arranged at opposite sides of the positive or anode grid I3. In an arrangement of this type the grids I2 and I4 are controlled in anti-phase relation 'due to the fact that a phase reversal takes place between the first and second control in a manner' similar to that of an ordinary triode amplifier. Since, however, the second 'control potential on the grid I4 is substantially amplied, the control bythe seco-nd grid may be vcaused,tovpredominate over the control by the `-zfffirst grid by properldesign of the circuit elements,

'resulting .in a considerable increase of amplifica- Vtion." In the arrangements according to Figures 1 .31 on the other hand, the grids I2 and I4 are ofthe steady positive potential'is possible due i to theifactthat the total anode current passing currents flowing to the positive grid 'I3 and to;

thejanodeis efectedby. asyarying' relative distributionv ofKV th'etotal discharge y currentV `in ac. cordance with the applied control potential.;4 I.

t, In the circuit arrangement Y according td, Figures l and 2, a direct current feedbackexists Adue, to the fact that the potential variationsjofthe, secondY control grid v I4 react `upon ,f theY yspace charge or anode grid |53. This reaction is yminis; mized :according to FiguI-efby theprovision of. a screen grid 2,6 arrangedbetweenthe inputigl'id3- I2 -zand the second controljgrid I4 and connected to agrsuit'able positive pointr of the highgpotentialj source such asa, tap point of the potentiometer resistance .I3 as shown. .By controlling thel potential of the screen grid 26 such Aas byvarying1 the-voltage drop or bleeder resistance 26( placed inthe screen: gridlead itis possible to ,adjustL the, direct f current reaction requirements. Y h y h According to a modiiication van increased con- 4to suit any existing.

trollingv action ofthe inputgridis obtained byv employing an input grid located near the cathode;

' and by deriving amplied potential from -a posi tively biased oranode grid spaced therefrom in; thev direction of the anode. p. A circuit arrange-- ment of this type is'shown in Figure 4. In the:

latter the input grid I2 islocated near the cath-l ode and rtl'ievpositive grid I3 placed nexttothe,Y

second control gridv I4. The screen grid in thisl modication is arranged lbetween thek inputv grid; I2 and-the positive ,grid- I3. Alternatively, the screenl grid may be. placed betweenI the ,positivej grid'- 13C-andthe second control K grid |247 such as; 75

.excited in' like phase since the current to the in Figure 4 in view of the location of grid I3 on the, opposite side of the input grid I2.

. In a circuit according'to Figure 5 wherein-the.

screen grid 2 6-is placed between'the positive grid I 3 and the second controlgrid I4, the direct Acurrent reaction between these grids is substantially reduced. If nevertheless in an arrangement of this type a certainv amount of reaction is desired a separate exterior feedback circuit may be provided lj such vas shown in Figure 6. In the latter, the anode I5 is directly connected to the input. grid I2 through a resistance 29. r'I'he effect of the anodepotential on the input grid i-s com` pensatedbya suitable counter potential derived' in the example shown l from thel potentiometery resistance 2l) which also` serves for compensating@ thepositive potential 'on the second control grid I4. order to adjust the compensating potential, there is provided a voltage divider 30 connected between the input 'grid' I2 and the negative terminal of the. compensating potential to the grid I2 on the one hand and to a variable tap point of the potential divider 30. In order to develop feedback potentials at the anode/'I5 5 therei's provided a -suitableload resistance28 in inverting "valveis used .between the outputof thep'ositive grid I3 and thefsecond control grid pressed upon the second control grid I4 yof the. amplifier I0 being of similar design to that in the preceding embodiments. v`For this purpose y the anode of the valve.32 is further connected .to4

source,v the input impedance VI3 being connected In this case,- itwould not suiice'to' provide one or more screen grids to eliminate'reaction and according to a' further rfeature of 'the invention al special phasev A circuit -arr'angement :of this type is shown in Figure 7. Inthe latter, the amplified poten-Y the negative pole of the compensating potential source 20 through a potentiometer resistance 31 and a variable tap of the latter is connected to the second control grid I4 of valve I0. By this connection, the effect of the high potential on the anode 35 of valve 32 upon the grid I4 of valve I is compensated in a manner readily understood from the above.

According to a further modification, the number of amplifying stages may be increased or the electron discharge current controlled at more than two points by the same potential such as shown in the exemplications according to Figures 8 and 9. In Figure 8, the cathode II, input grid I2, positive grid I3 and second control grid together with load resistance 2l and compensating potentiometer 22 constitute a two-stage direct coupled amplifier substantially similar as shown in Figures l and 3. In order to obtain additional amplification in the same valve, there is provided a further positive grid I3 having connected thereto a load resistance 2I and compensating resistance 22 in a manner substantially similar as the iirst positive grid I3. The compensating resistance 22 has a variable tap connected to a further control grid I4. Any desired number of additional amplifying stages may loe provided in this manner as will be readily understood. In the example illustrated a fourstage amplifier is shown, the corresponding elements of the separate stages being identified by similar but primed reference numerals as used for the first two amplifying stages.

Referring to Figure 9, there is shown a multistage amplifier similar to the preceding embodiment wherein the grid electrodes for the several amplifying stages are arranged relatively as shown in Figures 4 and 5. In the latter arrangement, a phase reversal by 180 takes place between successive amplifying stages while in case of Figure 8 all the controls of the common electron stream by the grids I2, I4, Id', I4, etc., act in the same sense as will be readily understood from the above. The function of the screen grids and other elements is substantially similar as described in connection with the two-stage amplifier shown in the preceding diagrams.

The arrangements described hereinbefore are specially suited for the amplification of variable direct potentials or currents. Thus, the amplifiers may be used in the measuring art or for amplifying control potentials such as AVCv (automatic volume control), AFC (automatic frequency control) potentials, volume expanding potentials in radio'receivers or the like. In many cases an existing multi-grid valve for low frequency or high frequency amplification may be used additionally as a multi-stage direct coupled amplier for amplifying a potential serving to control the operation of the amplifier. In this manner it is possible to `effect substantial variations of the alternating current amplification with a comparatively weak control potential with a minimum of Valves and circuit elements.

In Figure l2 there is shown a graph illustrating the variation of the anode current in an amplifier of the aforedescribed type Ain dependence upon the direct potential applied to the input of the valve such as in a circuit of the type according to Figures l, 2 and 3. As is seen, a variation of the direct grid potential by about .5 volt is sufcient to change the amplification from Zero to its maximum value. The amplification of an alternating potential which may be additionally applied to the input grid is determined bythe known operating characteristic of the valve. The auxiliary grids I3 and I4 in this case employed for the additional direct current amplification should be by-passed or grounded forthe alternating potential by means of condensers.`

If in the arrangements according to Figures 1 to 8 suitable alternating current circuits are connected to the input grid and to the anode such as is customary in low frequency or high frequency amplifiers, and if a direct control potential is simultaneously impressed upon the input grid there is obtained in this manner a low frequency or high frequency amplifying stage particularly well adapted for automatic volume control and/or volume expansion. The degree of the direct current amplification may be varied by suitably adjusting the values of the resistances 2| and 22 between substantial limits.

The high sensitivity of the adjustment of the amplication by small variations of direct potential makes it possible further to obtain .an automatic volume control without requiring `an additional AVC or outside control potential or in other words to provide a self-regulating or limiting amplier. For this purpose it is only necessary to adjust the operating point upon the curved part of the characteristic for the input grid I2 in such a manner as to cause a partial rectification of the applied alternating potential resulting in direct potential variations on the positive grid electrode I3. These potential variations, depending on the location of the electrode, may serve to effect an amplitude limitationor increase of the alternating potentials derived from the anode.

An exemplication of a circuit of this type is shown in Figure Il0. In the latter, if the valve used has a curved mutual characteristic representing current in the circuit of the positive grid I3 as a function of the potential on the grid I2, a partial rectification of the alternating potential impressed across the transformer 40 will take place resulting in corresponding variation of the steady potential on the grid I3. As the amplitude of the impressed alternating potential increases, the direct potential on the grid I3 becomes less positive in such a manner that the amplied direct potential on the grid I4 will become more negative. resulting in a decrease of the electron discharge current flowing to the anode I5. In this manner, the amplified alternating output current translated through the tuned transformer 42 to the output terminals c, d is automatically maintained at a predetermined level in a manner similar to the operation of known automatic volume control systems but Without requiring a separate external -control potential produced b-y a separate rectifier in a manner well known. The partial rectieation of the input alternating potential may also be effected in a different way such as by rectification in the grid circuit or in any other suitable manner. In an arrangement of this type the control potential applied from the grid I3 to the grid I4 should be sufficiently ltered such as by the provision of ground by-pass condensers 44 and il if the control is to be dependent upon the average amplitude of the alternating potential rather than upon its fluctuations or modulation. Condensers 45 and 46 are the usual grounding or by-pass condensers for the screen grid 26 and the high tension supply source, respectively.

The fact that by an arrangement according to the invention, provided the resistances 2| and 22 vare properly designed, it is possible 'to secure a sudden increase in amplification by means of a small variation of a control potential while with further increase of the control potential in the same sense the amplification is only slightly afis blocked for small control potentials and suddenly assumes its full amplification at a determined potential which may be adjusted to suit any existing requirements. An example of an arrangement of this type is illustrated in Figure 11. In the latter, the `low frequency potential to be amplified is applied through coupling condenser 48 to the input gridI2 and the amplified output potential derived by means of coupling condenser 52 and coupling resistance 53 in a manner well understood. The output potential may be applied to a succeeding stage of amplification or to a suitable translating device. The direct current amplifier is of the type to effect a phase reversal between successive amplifying stages whereby with the AVC potential Er impressed to normally render the grid I2 negative as shown in the drawings, the tube will be blocked for small values of the negative grid potential and become conductive .with increasing control potential. If the control potential is further increased, the amplication again begins to decrease provided a valve is used having a regulating or variable mu characteristic for the first or input grid. This decrease in amplification enables an efficient volume control by reason of the fact that the decreaseis inversely proportional to the output potential of the preceding high frequency amplifier; In Figure 13 is shown a graph further explaining the operation of Figure 1l representing anode current as a function of input grid potential in a two-stage direct coupled amplier of the type provided in Figure 11 and generally illustrated in Figures 4, 5, 6. This graph differs from Figure l2 corresponding to circuits of the type of Figures 1-3 by a reversal of the output phase as explained herein#- before.

It is evident from the above that the arrangements according to the invention are susceptible of numerous modifications and variations coming within the broader scope and spirit of the invention. Thus, it is possible to provide further grids or auxiliary anodes within a valve serving to produce additional effects or to construct the electrodes in any desired form. Furthermore, the circuits shown may be embodied in a reex amplifier using the same valve for radio, audio and direct current amplification. When simultaneously using a valve for amplification of a direct potential and alternating potential as described herein, it is also possible to apply the input potential to separate grids; that is, to apply the alternating potential to one grid and the direct potential to another input grid. It is also possible to derive the amplified alternating potential from one of the positive grids I3, I3', I3", etc., instead of from the anode circuit or simultaneously from bo-th or one or more of the positive grids. In the latter case the positive grid used for deriving alternating potential should not be by-passed or grounded for the potentials to be derived and in addition a suitable filter should `be provided to prevent the alternating potential from being impressed upon the succeeding control grid. The arrangements described for direct current amplification, especially those embodying positive reaction are also suited for generation of oscillations, both sinusoidal oscillations by the provision of suitable capacities and self-induction coils and for the generation of relaxation oscillations as used in television.

In order to avoid in the arrangements shown excessive control swings of the grid I3 beyond the negative region and to prevent appreciable grid currents, the control potential may be impressed upon this grid through a high ohmic resistance in which case the grid is preferably grounded or by-passed for high or low frequency;

Referring to Figure 14, there is shown a re' ceiving circuit for broadcast signals embodying an improved automatic volume control arrangement according to the invention. The signals absorbed by an antenna 55 are impressed through a tuned coupling transformer 56 upon the grid- -cathode path of a multi-grid amplifying valve I0 of the type described hereinbefore. The amplied high frequency signals are segregated by means of a tuned transformer 58 in the anode circuit of the valve and impressed upon a pair of diode rectifiers Ill and 'II in parallel through coupling condensers I2 and i3, respectively. The

output of the rectifier II is fed through a network comprising a smoothing resistance 18, smoothing condenser and volume. control po-` tentiometer I9 to an audio amplifier 8| having 4its output connected to a suitable translating device such as a loud speaker 82. The rectifier 'Ill serves to produce AVC potential applied through resistancesv'M and 'I5 to the grid I2 of the valve Ill in such a manner as to normally maintain the grid positive relative to the cathode. This AVC potential which may be of relatively small value compared with AVC potentials re` quired in the known AVC arrangement in use today is amplified by the tube I0 acting simultaneously as a direct coupled multi-stage ampli@V fier in accordance with the invention, as described in detail hereinbefore. For this purpose the positive grid I3 is connected to a suitable tap point of the potentiometer resistance 64 while the second control grid I4 is connected to a tap point of a further potentiometer resistance 65 in series with the first resistance 64 and connected to the positive pole of the high potential or anode current supply source on the one hand and the negative potential or ground on the other hand. Item 59 represents a compensating resistance in the cathode lead by-passed for highv frequency by a condenser 6I and serving to eliminate the effect of the high potential on the control grid I4. Both the positive grid I3 and the second control grid I4 are by-passed to ground for high frequency by by-pass condensers 56 and 61, respectively.

In the afore-described arrangement, variations of the AVC potential Er supplied by the rectifier 10 will cause similar variations of the potentials on the grids I3 and I4 in such a manner that by a slight decrease of the negative bias of the input grid I2 (slight increase of the AVC' potential), the negative potential of the grid I4 increases to such an extent as to substantially decrease the anode current due to the current distribution control. By suitable design of the circuit elements and operating potentials it is possible to effect a change of the degree of amplification between a minimum and maximum by varying the control potential Er from .5 to- 1.5 volts.

As will be evident from the foregoing the novel circuit according to the invention is susceptible of various other modifications and applications coming within the broad scope and spirit of the invention as dened in the appended claims. The specification and drawings are accordingly to be regarded in an illustrative rather than a limiting sense. Thus, the cathode heating and plate potential supply sources, by-pass condensers or choke coils to prevent direct or alternating currents from entering certain circuit portions but to enable them to readily pass through other circuits of the system, and other conventional elements and details have not been shown as being immaterial to the understanding of the invention and for clarity of disclosure and simplification of the drawings.

I claim:

1. In a combined alternating. current-direct current amplifier, an electron valve having a cathode, an anode and a plurality of grids located at different points in the electron stream passing from said cathode to said anode, alternating current input and output circuits operatively connected to an input grid and to said anode, respectively, for amplifying an alternating current signal, further means for impressing direct potential variations upon a rst grid of said valve, means comprising a load resistance and a source of positive potential connected to a second grid to produce amplied direct potential variations at said second grid, a conductive coupling connection from said second grid to a third grid of said valve, means to compensate the effect upon said third grid of the positive potential at said second grid, and further means to prevent alternating potential from affecting said third grid. i

2. In a combined alternating current-direct current amplier, an electron valve having a cathode, an anode and a plurality of grids located at different points in the electron stream passing from said cathode to said anode, alternating current input and output circuits connected to a first grid and to said anode, respectively, for amplifying an alternating current signal, further means for impressing direct potential variations upon said rst grid, means comprising a load resistance and a source of positive potential connected to a second grid to produce amplified direct. potentials at said second grid, a conductive coupling connection from said second grid to a third grid adapted to control the operation of said valve, means to compensate the eifect upon said third grid of the positive potential at'said second grid, and further means for preventing alteranting potential from affecting said third grid.

3. In a combined alternating current-direct current amplifier, an electron valve having a cathode, an anode and a plurality of grids located at -dilerent points in the electron stream passing from said cathode to said anode, alternating current input and output circuits connected to a first grid and to said anode, respectively, for amplifying an alternating current signal, means for producing a direct potential varying according to the average amplitude of the alternating current beingamplified, means for impressing said direct potential upon said first grid, further means comprising a load resistance and a source of positive potential connected to a second grid to produce amplied direct potential at said second grid, a conductive coupling connection from said second compensating the eie'ct upon said third g'rid'of the positive potential at said second grid,va`nd means to prevent alternating potential from affecing said third grid. l

4. In a combined alternating current-direct current ampliiier, an electron valve comprising a cathode, an anode, a rst grid located near said cathode, alternating current input and output circuits connected to said grid and anode, respectively, `for amplifying an alternating current signal, means for producing a direct potential `varying in accordance with the average amplitude of the alternating current being ampliedpmeans for impressing said direct potential upon said rst grid in negative polarity relation to said cathode, further means comprising a load resistance and a source of positive potential connected to a second grid spaced from said rst gridin adirection towards the anode to produce amplied direct potential variations at said second grid, a conductive coupling connection from said second grid to a third grid adapted to control the amplifying gain of said valve, means to compensate the `effect upon said third grid of the positive.V

potential at said second grid, and means to prevent alternating potential from aifecting said. second and third grid.

5. In a combined alternating current-direct current ampliiier, an electron valve having ya cathode and an anode, a rst grid located nearI said cathode, input and output circuits connected to said grid and said anode, respectively, for amplifying a modulated carrier signal by said valve, means for producing a direct control potential varying in accordance with the carrier amplitude of said signal, means for impressing said control potential upon saidl grid in positive polarity relation to said cathode, further means comprising a load resistance and a source of positive potential connected-to a second grid spaced from said rst grid in a direction towards said anode to produce amplified direct potential at said second grid, a conductive coupling connection from said second grid to a third grid near said anode adapted to control the amplifying gain of said valve, means to compensate the effect upon said third grid of the positive potential upon said second grid, and means to prevent carrier potential from' affecting said second and third grids. Y

. 6. In a combined alternating current-direct current amplifier, .an electron valve having ka l cathode and an anode, a rst grid located near said cathode, input and output circuits connected to said grid and said anode, respectively, for amplifying a modulated carrier signal by said valve, means for producing a direct control potential varying in accordance with the carrieramplitude of said signal, Ameans for impressing said control potential upon said first grid in positive polarity relation to said cathode, further means comprising a load resistance and a source of positive potential connected to a second grid spaced from said rst grid in a direction toward said anode to produce amplified direct potential at said second grid, a conductive coupling 'connection from .said second grid to a Athird grid, means for compensating the effect upon said third grid by the positive potential at said second grid, and means to prevent carrier potential fro affecting said second and third grids. '7. A self-regulating amplifying stage comprising an electron valve having a cathode, an anode and a plurality of grids located at diierent' points in the electron steam passing from said cathodeA source of positive potential connected to av second grid spaced'from said first grid in a direction towards the anode, the mutual operating characteristic for said second `grid in relation to said first grid being such as to produce a rectified negative potential at said second grid varying ,in proportion to thev average amplitude of the alternating potential to be amplified impressed upon said iirst grid, a direct current coupling connection from said second grid to a third grid spaced therefrom in a direction towards rthe anode and adapted to control the amplifying gain of saidrvalve, means to compensate the elect upon said third grid of the positive potential at said second grid, and further means to prevent alternating potential from aecting said third grid. l

r8. A self-regulating amplifying stage comprising a multi-grid electron valve having input and output circuits operatively connected thereto for amplifying oscillatory signal energy, means operatively connected with one of the grid electrodes of said valve other than the input grid for producing thereon a rectied negative potential varying in proportion to the average amplitude of the energy to be amplified, a conductive coupling connection from said last grid to afurther grid electrode adapted to control the amplifying gain of said valve, andmeans to prevent oscillatory potential from affecting said grid electrodes. l l

9. An electrical system comprising anjelectron discharge tube having a cathode, an anode and at least three grids located in the path of the electron currentv passing from said cathode to said anode, space current supply means for` mainrent potentials with respect to said cathode, a

source of signal energy, means for coupling said source to said first control grid and cathode, load impedance means connected to said anode grid to develop signal potential variations on said anode grid, means for applying the signal potential on said anode grid to said second control grid, and a signal output circuit connected to said anode and cathode.

12. A direct current amplifier comprising an electron discharge tube having a cathode, an anode grid, a first control grid, a second control grid and an anode, all arranged in spaced rela tion in the order named with respect to said cathode, space current supply means for maintaining said anode grid and said anode at positive direct current potentials with respect to said cathode, means for impressing a varying direct current potential between said rst control grid and said cathode, direct current load impedance means in the output circuit of said anode grid to develop potential variations pro,- portional to said impressed potential on said anode grid, a conductive coupling connection from said anode grid to said second control grid, means to compensate the effect upon said second control grid of the steady potential on said taining a iirst of said grids at a positive potential with respect to thecathode, a source of modulated carrier signals coupled to a second grid and the cathode, a signal output circuit coupled to said anode and said cathode, means including load impedance means connected to said first grid to developa potential at said rst grid varying in proportion to fluctuations of the carrier component of said signals, a direct conductive coupling connection from said first grid to the thirdrgrid, and means to compensate the eiiect of the positive 'potential of said first grid upon Said third grid.

10. An electrical system comprising an electron discharge tube having a cathode, an anode and at least threeA grids located in the path of the electron current passing from said cathode to said anode, space current supply means for maintaining a iirst of said grids at a positive potential with respectl to the cathode, a source of modulated carrier signals coupled to a second grid and the cathode, a signal output circuit coupled to said anode and said cathode, means including load impedance means connected to said first grid to developfa potential at said iirst grid varying in proportion to fluctuations of the carrier component of said signals, a direct conductive coupling connection from said first grid to the third grid,l meansto compensate the effect of the positive potential of said first grid upon said third grid, and a screening electrode intervening between said first and third grids.

11. An electrical amplifier comprising an electron-dischargetube `having' a cathode, an anode anode grid, and a signal output circuit connected to said anode and cathode.

13. A direct current ampliiier comprising an electron discharge tube having a cathode, an anode grid, -a first control grid, a second control grid and an anode, all arranged in spaced relation in the order named with respect to said cathode, a source of space current connected across said anode and cathode,.a resistive impedance inserted between said cathode and said source, means for impressing positive bias potential from said source upon said anode grid, means for impressing varying direct current potential between said first control grid and a point of said impedance close to said cathode, direct current load impedance means connected l to said anode grid to develop potential variations proportional to said impressed potential on said anode grid, a conductive coupling connection from said anode grid to said second control grid, and a signal translating device inserted in the anode circuit of said tube.

14. A direct currnet amplifier comprising an electron discharge tube having a cathode, an' anode grid, a rst control grid, a second control grid `and an anode, a source of space current connected across/said anode and cathode, a resistive impedance inserted between said cathode and said source, means for impressing positive biasing potential from said source upon said anode grid, means for applying varying direct current potential between said control grid and a point of said impedance close to said cathode, direct current load impedance means connected to said anode grid to develop potential variations pro-` portional to said impressed potential on said anode grid, a conductive coupling connection from said anode grid to said second control grid,

and a signal translating device inserted in the tube having av cathode, anianode and a plurality f of grids located at different points in the electron stream passing from said cathode to said anode, alternating current input and output circuits operatively connected to an input grid and said anode, respectively, for amplifying an alternating current signal, means for impressing direct current potential variations upon a rst grid of said tube, means comprising a load resistance and a source of positive potential connected to a second grid to produce amplified direct current potential at said second grid, a conductive coupling connection from said second grid to a third grid of said tube, and means to compensate the effect upon said third grid of the steady potential on said second grid.

16. A direct current amplifier comprising an electron discharge tube having a cathode, an anode grid, a first control grid, a second control grid and an anode, space current supply means for maintaining said anode grid and said anode at positive direct current potentials With respect to said cathode, means for impressing a direct current input potential between said first control grid and said cathode, direct current load impedance means connected to said anode grid to develop potential variations proportional to said impressed potential on said anode grid, a conductive coupling connection from said anode grid to said second control grid, means to compensate the effect upon said second control grid of the steady potential on said anode grid, said control grids and said anode grid being relatively arranged so that potential variations on said second control grid are substantially in phase With the input potential variations on said first control grid, and a signal output circuit connected to said anode and cathode.

HEINZ BOUCKE.

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