US2392415A

US2392415A - Balanced amplifier system

Info

Publication number: US2392415A
Authority: US
Publication date: 1946-01-08
Anticipated expiration: 1963-01-08

Description

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ATTORNEY Patented Jan. 8, 1946 BALANCED AMPLIFIER SYSTEltI Walter Soller, Cincinnati, Ohio, assigner of onehali' to William H. Woodin, Jr., San Mateo,

Calif.

Application April 5, 1944, Serial No. 529,663

Claims.

My invention relates broadly to balanced amplililer systems and more particularly to circuit arrangements for balancing multi-stage amplifier systems. I

One of the objects of my invention is to provide a system for coupling multi-stage amplifier circuits involving multiple grid tubes having means for electrically balancing the circuits of each amplification stage.

Another object of my invention is to provide a multi-stage electron tube amplifier system having means in each of the stages for compensating for changes in electron emission and changes in power supply tending to vary potentials on the anode or multiple grids of the tubes in the separate stages of the amplification system.

Still another object of my invention is to provide circuit arrangements for multi-stage amplifier systems each involving a multi-grid tube having means for electrically balancing each tube and each amplifier stage for avoiding detrimental effects arising from changes in power supply voltage and electron emission in the several stages of a multi-stage amplifier system.

A further object of my invention is tc provide a system for electrically balancing multi-stage electron tube amplifier systems embodying multigrid tubes in which cathode emission is compensated in each of the stages of the amplifier system.

Still another object of my invention isto provide an arrangement of multi-stage electron tube amplifier system employing multi-grid tubes having resistance network arrangements for coupling the several stages of the amplifier in such manner that a highly stabilized condition of operation of the amplifier system is maintained.

Other and further objects of my invention reside in arrangements of resistance networks for coupling the stages of multi-grid amplifiers as set forth more fully in the specification hereinafter following by reference to the accompanying drawings, in which:

Figure 1 shows one embodiment of my invention applied to a multi-grid multi-stage amplifier system embodying my invention; Fig. 2 shows a modified form of balanced amplifier embodying my invention; Fig. 3 shows a further modified form of multi-stage amplifier circuit operating in accordance with my invention; Fig. 4 shows a still further form of multi-stage amplifier embodying my invention; and Fig. 5 shows still another arrangement of balancing system for multi-grid amplifier stages operating in accordance with my invention.

Referring to the drawings in detail, reference character I designates a multi-grid tube constituting the first stage of the balanced amplifier system of my invention. Pentode tube i includes cathode 2 which is heated to electron emitting temperature by operation of heater 3, space charge grid l, screen grid 5, control grid 6, auxiliary grid 1 and anode 8. The input circuit for pentode I is represented at 9 connected through adjustable resistances I 0 and II with cathode 2 at one side and connected to control grid 8 at the opposite side. A tap I2 between the adjustable resistances III and I I connects to the space charge grid 4 for effecting a balance of the individual circuit of pentode I in compensating for variations in electron emission for cathode 2. The details of this particular compensation circuit are set forth more fully in ccpending application Serial No, 483,351, filed April 16, 1943, by Richard P. Krebs, to which reference is made for a more complete understanding of the compensation for variation in electron emission in the individual tube circuit per se.

The auxiliary grid 'l is connected with cathode 2 through connection I4 as shown. The output from pentode I connects with anode 8 to one terminal of the adjustable coupling resistor I5. The opposite terminal of the adjustable coupling resistor I5 is connected through adjustable resistor I6 with the screen grid 5. 'I'he output circuit of tube I is then completed through adjustable resistance I 'l and tap I8 to the positive side of the direct current power supply circuit that I have represented generally at I9. The negative side of the direct current power supply circuit I9 returns to the cathode 2 through adjustable resistances I0 and I I as shown and is connected to ground at 20 as shown.

I'he difficulty of applying the output of tube I constituting one stage of amplification to the input of a succeeding tube constituting another stage of amplification is that the second stage is subjected to such relatively high `potential that the operation of the second stage may become unstable. To overcome this l. provide a supplemental tube circuit in the first stage of the amplifier circuit including the pentode tube shown at 2l. Pentode tube 2| contains cathode 22, heater electrode 23, space charge grid 2l, screen grid 25. control grid 28, auxiliary grid 21 and anode 28. The control grid 26 oi' pentode 2| connects directly to ground 2D as shown. Tube 2l is very carefully balanced within its own circuit through operation of adjustable resistors 30 and 3l in circuit with cathode 22 and

adjustable resistors

28 and 31 in circuit with the screen grid 2B and anode 28 as shown. The adjustable resistor 8| is arranged for compensating for variations in emission for cathode 22 under conditions of variation in the heater supply as heretofore explained in connection with pentode I.

The second stage of amplication is represented by pentode 4I including cathode 42 heated by heater electrode 43, space charge grid 44, auxiliary grid 41, screen grid 45, control grid 46 and anode 48. The input circuit to pentode 4| connects to the terminal of adjustable resistor I5 in the output circuit of pentode I and to the lower terminal of adjustable resistance 31 and through adjustable resistance |1 to the lower terminal oi' adjustable resistance I5. The input circuit for pentode 4| includes adjustable resistors 50 and 5| arranged as shown, adjustable resistor 5I is disposed in series between cathode 42 and space charge grid 44 and serves for compensating for variations in electron emission of cathode 42 due to variations in the heater supply energy as heretofore explained. In effect, control grid 46 and cathode 42 of pentode 4| are connected to the

anodes

8 and 28 of pentodes I and 2|, respectively. The power supply for operating the amplification stage containing pentode 4| isrepresented at 52 across which adjustable

potential divider resistors

53, 54 and 55 are connected. The cathode 42 of the pentode 4I is connected to the negative terminal of the power supply circuit 52 through adjustable resistors 58 and 5| while the anode 48 is connected with the positive terminal of the power supply circuit through adjustable resistors 56.

The tap 51 intermediate

adjustable resistors

53 and 54 in the potential divider circuit connects through adjustable resistors 56 and 58 with the auxiliary grid 41. The output circuit from the second stage of amplification is connected between anode 48 and the tap 68 intermediate adjustable resistors 59 and 58 in the auxiliary grid Icircuit. The output circuit is shown at 6| leading to the next succeeding amplier stage or to the current utilization stage.

II'he heater supply for each of the cathodes connects to the circuits represented schematically at 3a, 23a and 43a.

By the arrangement shown, the entire second stage rides at the potential of the supplemental pentode circuit 2| which is the zero balancing potential from ground of the first pentode tube circuit I. Therefore, only the amplied input voltage remains between the control grid 46 and the negative terminal of the direct current power supply 52 of the second stage.

Fundamentally the circuit oi.' Fig. 1 includes a Wheatstone bridge balance circuit with the additional provision for compensating for emission which by means of the

additional grids

4 and 24 in tubes .and 2l may be accurately controlled. The resistances forming the arms of the bridge are the plate resistances of tubes I and 2| and the two lo`ad resistors I1 and 31. The power supnon of the wneatscone bridge circuit.

The input circuit to the Wheatstone bridge at 8 connects across the control grid 6 o! tube and to the cathode o! tube I through 'adjustable resistors |8| I, the input circuit being grounded at 20. The output circuit for the apparatus comprises the current measuring ampliiler 4|, the input circuit of which connects across

plates

8 and 28 of tubes I and 2|. Balance is obtained by balancing the bridge by snorting the input out and then balancing the bridge by adjusting resistors |1 and 31 until no voltage appears across

plates

8 and 28. This balances and takes care of the changes in the rst direct current supply voltage. The emission compensation is accomplished by adjusting resistors |I| and Il, 36 and 3|, each tube independently. The second amplifier 4| is typical of the balance circuits shown in the several gures of the drawings.

In Fig. 2 I have shown a similar balancing circuit arrangement except that more precise balancing is secured by rearrangement of the 'circuits to the tube electrodes and the circuit elements connected with the tube electrodes. It will be observed that the circuit oi tube is rearranged so that balancing is effected by the auxiliary grid 1 disposed between the space charge grid 4 and the screen grid 5. The auxiliary grid'-1 is connected to tap 63 in the circuit which includes adjustable resistor I6, adjustable resistor 64 and adjustable resistor 65 connected to ground 66. In this circuit path the screen grid 5 connects to tap 61 leading to ground through the adjustable resistor 65. Thus shield grid 5 is maintained at ground potential while adjustable resistor 64 cony trois the potential at auxiliary grid 1 and screen grid 5. A similar rearrangement is made of the electrodes in tubes 2| and 4I. That is to say, a circuit path is provided from balancing resistor 36 through balancing resistor 14 and balancing resistor 15 to the negative side of the power supply source 52 and tap connections are taken from point 13 intermediate

adjustable resistors

36 and 14 to the auxiliary grid 21 of tube 2| and from tap 11 intermediate

adjustable resistors

14 and 15 to screen grid 25 arranged in the order explained with respect to tube |.v Additional balancing is obtained by the inclusion of adjustable resistor 18 in circuit with plate electrode 28.

Tube 4| shown in Fig. 2 corresponds to the tube described in connection with Fig. 1 and contains the same lelements except that the elements are arranged in the order heretofore explained for theelements of tubes and 2| in Fig. 2. The input circuit forl tube 4| in Fig. 2 extends from control grid 46 to the upper terminal of adjustable resistance |5 and from the cathode 42 through adjustable resistors 5| and 50 to the anode 28 of tube 2|., For further balancing the circuit of tube 4| with greater precision, I provide

adjustable resistors

68 and 69 arranged in circuit with anode 48 and auxiliary grid 41 as shown.

Each of the illament heating circuits are provided with adjustable rheostats 3b, 23h. and 43b in circuit with the heater supply, as shown. Precision balancing is obtained by adjusting the resistors shown and amplification is eiected under stabilized conditions despite the fact that a high potential is impressed upon the input cir'- cuit of the second stage. The supplemental tube circuit 2| operates to maintain the second stage constituted by tube 4| at a constant potential irrespective of substantial variations in the power supply.

I may apply the principles of my invention to tubes of the directlyv heated type, as` shown'in Fig. 3 in which tube elements numbered to correspond with similar tube elements, described in connection with Figs. 1 and 2, are shown in association with a directly heated cathode. That is to say, tube `I contains a directly heated cathode 19 associated with the space charge grid 4, the control grid 6, the screen grid 5, the suppressor or auxiliary grid 1 and the anode 8. The balanced circuits associated with the electrodes of tube I are generally similar to the circuits heretofore explained in that the input circuit 9 connects to the control grid 8 and the cathode 19 through the switch circuit 80. j For a further explanation of the switch circuit 80, reference is made to my Letters Patent 2,245,616, granted June 17, 1941, for Amplification system. The switch circuit 80 includes a switch arm that is movable to either position a or position b. In position a the switch arm short circuits the adjustable series resistance 88 in the filament or heater circuit while in the position b the switch arm serves to introduce adjustable resistance 89 in a shunt path with the filament 19. Thus the emission of the cathode 19 can be changed independently of the power source, which I have represented at 83 connected through adjustable rheostat 84 with the adjustable resistor 81 leading to one side of the cathode circuit terminating in the switch system 80 and through adjustable resistance 8| to the other side o1 the cathode circuit as shown.

'I'he space charge grid 4 is connected through adjustable resistor 82 with the cathode circuit for compensating for variation in cathode emission.

An independent source 85 is provided for energizing the other elements of the tube through adjustable resistance 88 as shown. A potentiometer or divider circuit is provided for applying selected potentials to the tube elements as represented at 90 and 9| connected across the power supply circuit energized from source 85. Tap 92 provides a connection through adjustable resistor 93 to screen grid 5. Adjustable resistance I8 connects between the space charge grid 4 and the positive side of the power source 85 through adjustable resistance 88, as shown. The output is delivered to adjustable resistance I5 from which connection is taken to the input circuit of the next succeeding stage oi' amplification embodying tube 4 I.

The emission from cathode 19 is maintained constantly under conditions oi variation in the applied power from source 83 or under conditions of other variations by adjusting

resistors

81, 8| and 82 until no change occurs in the emission when both switch 80 is thrown from position a to the adjustable resistors |08 and |09 for setting tht cathode circuit for constant emission. This is accomplished by adjusting resistors |01, IOI,

.andv |02 until no change occurs in the emission when both switch |00 is thrown from position a to position b and resistor |04 is adjusted. The

' other tube elements are energized in a manner position b and resistor 84 is adjusted. Proportional adjustments are made in the adjustable resistances in circuit with the other elements of the tube as explained in detail in my Patent 2,245,616 supra.

In order to maintain a constant potential at thegsecond stage of the amplifier constituted by tube 4|, I provide a supplemental tube 2| which corresponds with a correspondingly numbered supplemental tube 2| illustrated in Figs. 1 and 2 except for the rearrangement of electrodes and the inclusion of the directly heated cathode in lieu of the indirectly heated cathode illustrated in Figs. 1 and 2. Referring to tube 2| in detail, I have shown the directly heated cathode 99 arranged in a power supply circuit for obtaining constant emission of the same type described in connection with tube I, that is a switching device |00 is provided, movable to either position a or posisimilar to the arrangement described in connection with tube I, that is anode 28 connects through adjustable resistance 18 to the positive side of the power source 85 through adjustable rheostat 31. {I'he negative side of power source 88 terminates at the cathode 99 and is grounded at 88 as shown. The control grid 28 completes a path to the input circuit of the tube through adjustable resistance |01 as shown. The space charge grid 24 operates to compensate for variations in emission by adjustment of resistance |02. A balance is effected on screen grid by control of adjustable resistance II3. The required potentials for operating the anode circuit are determined by adjustment of resistors |I0 and III. The tap I|2 leads through adjustable resistor II3 to screen grid 25. The adjustable resistance I determines the potential between the space charge grid 24 and the anode 28. Tube 2| when adjusted holds the second stage, constituted by "tube 4I, at a constant potential. `'Iube 4I, as in the case of tubes I and 2|, includes elements corresponding to the elements as in Fig. 2 except that a directly heated cathode is employed. The cathode is shown at II8 arranged for constant emission under control of a power supply source similar to that described in connection with tubes I and 2|. That is a power supply source indicated at |23 is connected through an adjustable rheostat |24 to opposite sides of the cathode circuit through adjustable resistor II1 to switch system |20. movable either to position a or position b to effectively include or exclude resistances |29 or |28 in the cathode circuit.l The energy supplied to the cathode'circuit passes through adjustable resistance I2I to one terminal of which the adjustable resistance |22 connects' leading to the space charge grid |34. By adjusting resistor |22, compensation for variation in electron emission may be effected. One side of the cathode circuit connects through lead |21 to the plate electrode 28 of supplemental tube 2| while the control grid 38 connects to the terminal of adjustable resistor I5 that connects to plate electrode 8. High potential under conditions of great stability is impressed between control grid |38 and the cathode circuit as shown. A connection is taken from suppressor or' auxiliary grid I3`| to the cathode II8.` The output circuit connects between anode |38 and the screen grid |35 as shown. The power supply system for the elements of the tube as just described is completed from source |25 through adjustable rheostat |28 to the potentiometer and divider circuit represented by resistors |40 and I4I. Tap |42 connects through adjustable resistor I 43 to the screen grid |35 for applying the required potential thereto. Adjustable resistance 56 is arranged in the anode circuit in connection with anode |38 as shown. Adjustable resistance |48 determines the potential across space charge grid |34 and anode |88.

A high degree of stabilized amplication is thus mental tube circuit heretofore explained.

ampliiication of feeble currents despite the high potential existent across the input of the second stage of ampliiication.

In Fig. 4 I have shown a modiiiedcircuit arrangement arranged for accomplishing the objects obtained in the previous forms of the circuit of my invention but having a further degree of precision combination for variation in electron emission. In Fig. 4 I provide for additional compensation for electron'emission by including a further adjustable resistor |50 interposed between the space charge grid 4 and the circuit leading to the cathode 2 through adjustable resistor |I. In tube I I provide for additional balancing of the auxiliary grid 1 by means of adjustable resistor |5|. The power supply for the cuit which includes adjustable resistors 15, 'I4

Aand 36,` as shown. Variations in electron emis--` sion for tube 2| 'are adjusted with a high degree4 of precision by means of adjustable rheostat |53.

The plate circuit of supplemental. tube 2| connects tothe cathode system of the tube 4| con- L stituting the second stage of amplication. Provision is made for the compensation of variations obtained by eiecting the adjustment shown for will vary with the power supply. By arranging the second direct current supply so that it is insulated completely from ground, this connection between

resistors

50 and 53 will continually take on the voltage of the iirst stage without ever aii'ecting the input voltage on the second stage.

In the circuits shown in Figs. 1-4, the second stage is held at a definite voltage, that is, the voltage maintained by the supplemental tube circuit of the rst stage constituted by tube 2|.

The majorucompensation for emission change is accomplished independently of the compensation of voltage changes making complete balancing of the system easier of accomplishment.

The electrodes of tubes I and 4| are arranged as explained in Figs. 2 and 4 with similar circuit elements. Provision is made however for independently balancing the circuit to the screen grid 5 by means of adjustable resistor |55 connected to tap 61 in the potentiometer or divider circuit containing resistors I6. 64 and 65. Independently adjustable balancing resistor |55 is connected between tap 63 in the same circuit and the auxiliary grid 'I with the additional adjustin electron emission in a manner similar to that explained in connection with tubes and 2 I, that is by the arrangement of adjustable resistance |54 disposed in circuit between the space charge grid 44 and the cathode 42 as shown.

The energization for the other elements of tube 4| is obtained in a manner similar to the arrangements heretofore explained so that an amplified outputvis delivered at 6| under conditions of vgreat stability.

In Fig. 5 I have shown a further improvement in the amplification system embodying my invention in which the pentodes and 4| -constituting the iirst and second stages of the amplifier system are coupled without the aid of the supple- The separate tubes and 4| in Fig. 5 are individually balanced. This arrangement is radically diierent from the coupled circuits of my Patent` stage tube goes through resistances of the circuit of the first stage. Therefore, changes in the second stage cathode current, due to power supply,

vvoltage and emission changes, will affect the output of the ilrst stage. The compensation for these changes in the nrst stage are then taken care of in the balancing of the second stage. That is, the balancing of the two stages are not independent of each other.

In Fig. 5 the circuit arrangement is such that not only each stage but each type of variation, the voltage on the elements and the emission, is balanced independently.

In the circuit of Fig. 5 the entire second stage floats with respect to the rst stage.

Variations in emission and voltages due to the changes in power supply voltage of the rst stage are compensated for in such a way that they will not appear in the voltage between the control grid and connection between

resistors

50 and 53. Voltage above ground of this latter connection able resistor 56 disposed in series therewith as shown for effecting precision balancing of the first' stage. This circuit will also function with In reviewing the several iigures of the draw-l ings, it will be seen that the first Stage,l 0f ampliflcation in Figs'. 1-4 is constituted by the pentode I including its cathode and anode and multiplicity of cold grid electrodes in association with the supplemental tube 2| having the cathode and anode thereof connected in multiple with the cathode and anode of the tube The output circuits of each of these tubes I and 2| in multiple connect to the control and cathode of the tube 4|. In effect the anode of tube connects to the control grid of tube 4| while the anode of tube 2| connects to the cathode of tube 4I. In Fig. l additional balance is obtained by an adjustable resistor disposed in circuit with the screen grid electrodes. In Fig. 2 additional balancing is obtained by an adjustable resistor disposed in circuit with the auxiliary grid electrode. In Fig. 3 additional balancing is obtained by including adjustable resistors in the control grid circuits of the several tubes, together with independently adjustable resistors in the Screen grid circuits thereof. In Fig. 4 additional balancing is obtained by including adjustable resistors in the Yauxiliary grid circuits, at the same time including additional adjustable resistors in each of the control grid circuits. In Fig. 5 wherein the separate stages are individually balanced, precision balancing is obtained by including independently adjustable resistors in series with the screen grid electrodes, the auxiliary grid electrodes, as well as the control grid electrodes.

f The circuits embodying my invention are shown in their general form. It is understood that any resistor shown in these circuits can have a resistance of zero ohms, if it is found that this condition is required for balance or correct compensation. One or up to three of the resistors, |50, |5|, |54, |55, |56 may'have zero ohms.

The circuit arrangements of my invention have proven highly practical in operation and while I have explained my invention in certain preferred embodiments, I desire that it be understood that modifications may be made and no limitations upon my invention are intended other than are imposed by the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States, is as follows:

1. A stabilized amplification system comprising a plurality of electron tubes each including a, cathode, a space charge grid, a control grid, a, screen grid, an auxiliary grid and anode electrodes, a power supply circuit for energizing said electrodes, circuits individual to the electrodes of each of said tubes, means for electrically balancing the circuits of each of said tubes constituting separately balanced stages, one of said stages including a pair of said tubes with the cathode and ancdes thereof connected in multiple and another of said stages including another of said tubes with the control grid electrically connected with the anode of one of said pair of tubes and the cathode electrically connected with the anode of the other of said tubes in said pair of tubes, and an output circuit connected between the anode and auxiliary grid of the tubein said last mentioned stage.

2. A stabilized amplification system comprising a plurality of electron tubes each including a cathode, a space charge grid, a control grid, a screen grid, an auxiliary grid and anode electrodes, a power supply circuit for energizing said electrodes, circuits individual to the electrodes of each of said tubes, means for electrically balancing the circuits of each of said tubes constituting separately balanced stages, certain of said tubes including independently adjustable means in circuit with the screen grid electrodes thereof, one of said stages including a pair of said tubes with the cathode and anodes thereof connected in multiple and another of said stages including another of said tubes with the control grid electrically connected with the anode of one of said pair of tubes and the cathode electrically connected with the anode ofthe other of said tubes, and an output circuit connected between the anode and auxiliary grid of the tube in said last mentioned stage.

3. A stabilized ampliiication system comprising a plurality of electron tubes each including a cathode, a space charge grid, a control grid, a screen grid, an auxiliary grid and anode electrodes, a power supply circuit for energizing said electrodes, circuits individual to the electrodes of each of said tubes, means for electrically balancing the circuits of each of said tubes constituting separately balanced stages, one of said stages including a pair of said tubes with the cathode and anodes thereof connected in multiple and another of said stages including another of said tubes with the control grid electrically connected with the anode of one of said pair of tubes and the cathode electrically connected with the anode of the other of said tubes in said pair of tubes, and an output circuit connected between two of the electrodes of the tube in said last mentioned stage.

4. A stabilized amplification system comprising a plurality of electron tubes each including a cathode, a space charge grid, a control grid, a screen grid, an auxiliary grid and anode elec.- trodes, a power supply circuit for energizing said electrodes, circuits individual to the electrodes of each of said tubes, means for electrically balancing the circuits of each of said tubes constituting l separately balanced stages, certain of said tubes including independently adjustable means in circuit with the screen grid electrodes thereof, one of said stages including a pair of said tubes with the cathode and anodes thereof connected in multiple and another of said stages including another of said tubes with the control grid electrically connected with the anode of one of said 5 pair of tubes and the cathode electrically connected with the anode of the other of said tubes in said pair of tubes, and an output circuit connected between twov of the electrodes of the tube in said-last mentioned stage.

5. A stabilized ampliiication system comprising a plurality of electron tubes each including a cathode, a space charge grid, a control grid, a screen grid, an auxiliary grid and anode electrodes, a power supply circuit for energizing said electrodes, circuits individual to the electrodes of each of said tubes, means for electrically balanci118 the circuits of each of said tubes constituting separately balanced stages, independently adjustable means in circuit with the auxiliary grid in each of said tubes, one of said stages including a pair of said tubes with the cathode and anodes thereof connected in multiple and another of said stages including another of said tubes with the control grid electrically connected with the anode of one oi' said pair of tubes and the cathode electrically connected with the anode of the other of said tubes iii said pair of tubes, and an output circuit connected between two of the electrodes of the tube in said last mentioned stage.

6. A stabilized amplification system comprising a plurahty of electron tubes each including a cathode, a space charge grid, a control grid, a screen grid. an auxiliary grid and anode electrodes,fa power supply circuit for energizing said electrodes. circuits individual to the electrodes of each of said tubes, means for electrically balancing the circuits of each of said tubes constituting separately balanced stages, means associated with the cathodes of each of said tubes for maintaining constant electron emission therefrom, one of said stages including a pair of said tubes with the cathode and anodes thereof connected in multiple and another of said stages including another of said tubes with the control grid electrically connected with the anode of one of said pair of tubes and the cathode electrically connected with the anode of the other of said tubes in said pair of tubes, and an output circuit connected between two of the electrodes of the tube in said last mentioned stage.

7. A stabilized amplification system comprising a plurality of electron tubes each including a cathode, a. space charge grid, a control grid, a screen grid, an auxiliary grid and anode electrodes, a power supply circuit for energizing said electrodes, circuits individual to the electrodes of eachl of said tubes, means for electrically balancing the circuits of each of said tubes constituting separately balanced stages, means associated with 50 the cathodes of each of said tubes for maintaining constant electron emission therefrom, independently adjustable means in circuit with each Iof said auxiliary grids for balancing each of said stages in said auxiliary grids, one of said stages o5 including a pair of said tubes with the cathode and anodes thereof connected in multiple and another` of said stages including another of said tubes with the control grid electrically connected with the anode of one of said pair of tubes and 70 the cathode electrically connected with the anode of the other of said tubes in said pair of tubes, and an output circuit connected between two of the electrodes of the tube in said last mentioned stalle. 7B 8. A stabilized amplification system comprising a plurality of electron tubes each including a cathode, a space charge grid, a control grid, a screen grid, an auxiliary grid and anode electrodes, a power supply circuit for energizing said electrodes, circuits individual to the electrodes of each of said tubes, means for electrically balancing the circuits oi each of said tubes constituting separately balanced stages, an adjustable resistor interposed between said space charge grid and said cathode for compensating for variations in electron emission from said cathode, one of said stages including a pair oi' said ,tubes with the cathode and anodes thereof connected in multiple and another oi' said stages including another of said tubes with the control grid electrically connected with the anode of one of said pair of tubes and the cathode electrically connected with the anode of the other of said tubes in said pair of tubes, and an output circuit connected between two oi' the electrodes of the tube in said last mentioned stage.

' 9. A stabilized amplification system comprising a plurality of electron tubes each including a cathode. a space'charge grid, a control grid, a screen grid, an auxiliary grid ,and anode Velectrodes, a power supply circuit for energizing said electrodes,cii'cuits individual to the electrodes acca-nc of each oli said, tubes, means for electrically bal ancingA the circuits of each of saidtubes constivtuting separately balanced stages, one of said #stages including a pair of saidl tubes with the cathode andianodes thereof connected in multiple and another of 'said stages including another ot said tubes with the control grid electrically connected with the anode of one of said pair of tubes and the cathode electrically connected with-the anode of the other of said tubes in said pair of tubes, an output circuit connected between the anode and auxiliary grid of the tube in said last mentioned stage, VYand an adjustable resistor in said last vmentioned connection for further balancing the operation of said circuits.

10. A stabilized amplification system comprising a plurality of electron tubes each including a cathode, a space charge grid. a control grid, a screen grid, an auxiliary grid vand anode electrodes, a power supply circuit for energizing said electrodes, circuits individual to the electrodes of each of said tubes, means for electrically balancing the circuits of each of said tubes constituting separately balanced stages. one of said stages including a pair of said tubes with the cathode and anodes thereof connected in multiple and another of said stages including another oi' said tubes with the control grid electrically connected with'the anode of one of said pair of tubes and the cathode electrically connected with the anode of the other of said tubes in said pair of tubes. an output' circuit connected between. the anode and auxiliarysrid oi' the tube in said last men- ;tloned stage, an adjustable resistor in said last mentioned connection for further balancing the 35"' operation of said circuits, andindependenuy ad' instable means in circuit with each of the screen grid electrodes of saidelectron tubes.

WALTER SOLI-IER.