US2447507A - Balancing circuit - Google Patents

Description

1948- D. E. KENYON 2,447,567

BALANC ING C IRCUIT Filed Jan. 16, 1946 Z SheetS-SheeI 1 STABILIZED C. VOLTHGE SOURCE Lona I2 IN SIGN/H. SOURCE PULSE WA? v5 eszvmmoe STflB/L/ZED D. C.

VOL THGE SOURCE &

1943- D. E. KENYON 2,447,567

BALANCING CIRCUIT Filed Jan. 16, 1946 2 SheetsSheet 2 INF T SIG/Vfll.

SOURCE If? 1% 'i 1 4 0 oazav/a/r yams STHEIL AZED a 6'. VOL 746E SDI/RC E INVENTOR TTORN EY Patented Aug. 2 1948 NH STATE rr-ic BALANCING CIRCUIT ware Application January 16, 1946, Serial No. 641,591

20 Claims. 1

This invention relates generally to current balancing circuits and systems and more particularly to a system for the automatic centering of the sweep in electronic circuits such as cathode-ray tube circuits.

Previous methods of stabilizing the sweep of an electron-beam deflecting device, specifically the direct current component-of the sweep amplitude of a cathode-ray tube circuit, required many cumbersome components such as reactors connected in shunt with the deflection yokes of this tube and coupled by direct current blocking capacitors. The deflection and position circuits were kept sep arate. These reactors were heavy and too bulky for the applications contemplated, and fidelity of pattern was lost due to-the use of inductances. Furthermore, variations in. these components were difiicult to overcome along with variations in the characteristics of sweep amplifier tubes. Therefore, a phase of the inven-tors motive for the present invention was dependent upon the existence of the above problems. Other motives for the present invention will be evident as the discus-- sion proceeds hereinafter.

Therefore, a primary object of the present inven tion is to provide apparatusto overcome all the above problems.

It is another primary object of this invention to provide an electronic circuit and apparatus adapted to produce a. current output of constant average magnitude to any load.

It is a further object of this invention to provide circuits and related means for continuously and automatically centering the electron beam in an electron deflection device.

A further object of this invention is to provide circuit arrangements which are adapted to produce balanced currents in the deflecting elements of an electron beam deflecting indicator.

A. still further object of this invention is to pro- Vide means to continuously and automatically balancethe direct current components of load current in a push-pull amplifier.

It is a further object of this inventionto provide circuit means which are adapted to keep the instantaneous current through the magnetic yokes of a cathode-ray tube equal at a predetermined instant of the sweep voltage.

The invention in another of its aspects relates to novel features of the instrumentalities described herein for achieving the principal objects of the invention and to novel principles e p y in those instrumentalities, whether or not these features and principles are used for the said principal objects or in the said field.

A further object of the invention is to provide improved apparatusv and instrumentalities embodying novel features and principles, adapted for use in realizing the above objects and also adapted for use in other fields.

A still further object ofthis invention is to provide circuits which are adapted to have a current output Whose direct current component is substantially constant even though the characteristics of the used tubes may change.

Generally speaking, this invention contemplates stabilizing a current or voltage wave applied to a load by sampling the wave either continuously or intermittently, then averaging that portion of the wave so sampled, and finally controlling in response to the averaged wave portion the direct component of the wave applied to the load to compensate or substantially reduce changes in the averaged wave portion.

Continuous sampling may be effected by a filter network conductively connected to a cathode resistor associated with the amplifiers feeding the load. Intermittent sampling may be obtained by a switch circuit which permits the filter network to respond only during predetermined intervals, preferably synchronized with the signal flowing through the load.

This invention necessitates the use of a pin.- rality of amplifiers so connected in a circuit to a load and stabilized voltage source that a change in the averaged direct current portion of the current passing therethrough, sampled on either a continuous or intermittent basis to one of these amplifiers, is automatically minimized. The inventor has found that this desirable result is possible when the averaged current in a first amplifier or power amplifier is taken from its cathode circuit in the form of a voltage at the remote or tube side of a grounded cathode resister and this voltage is impressed, via a filter or averaging circuit on the grid of a second or direct current amplifier or an electronic tube which has its cathode connected to a source of constant potential provided by a stabilizedvoltage source or by a resistive bleeder between a stabilized voltage source and ground and feeding the output of this last-mentioned amplifier through a negative feedback circuit back to the input side of the first or power amplifier.

In another aspect of the invention, circuit means are provided in a push-pul1 arrangement of the various amplifiers suitable for use in a situation such as a cathode-ray tube circuit or a power amplifier in which the problems of centering a defiectable electron stream on a screen in the first case and of automatically balancing out the direct current component in the primary winding of an output power transformer in the second case may exist. In the first case, the load mentioned above in all probability would be characterized by a coil associated with each deflection yoke of this cathode-ray tube. Since there are both horizontal and vertical deflection coils to be considered, two distinct circuits em ploying the push-pull arrangement of the inventors novel fundamental circuit would be used. The circuit for the horizontal deflection coils is a duplication of that for the vertical deflection coils and therefore only one circuit related to this topic has been shown and described hereinafter.

Some of the advantages of this invention as related to the latter topic are that it provides a method for automatically balancing the average current in each side of a push-pull magnetic deflection yoke, and the circuit concerned is especially useful in the push-pull amplifiers of cathode-ray tubes used in radio pulsing system-s although it is not limited in utility thereto.

Sampling the mentioned cathode voltage wave associated with the load intermittently or during recurrent intervals may be used with the above cathode-ray tube circuit application. In this instance, the circuit is for the purpose of keeping the direct current component of the instantaneous current through the magnetic yokes equal at a predetermined instant of the sweep voltage. This result is accomplished by sampling the cathode voltage during recurrent intervals which are synchronized with the application of the sweep voltage to the cathode-ray tube and the mechanism for doing such sampling is in the form of a cooperative arrangement of two discharge devices, one preferably being a diode with a high anode load resistor between the filter circuit and the tube side of the grounded cathode resistor on the power or first amplifier. This diode has connected thereto at its anode the other discharge device such as a triode triggered by a negative pulse of short duration timed with the sweep voltage deactivating this triode and thereby raising the anode potential of the diode to the discharge point. In other respects this circuit embodiment of an important phase of the inventors concept responds in a manner similar to the circuit described above. However, in the latter case the circuit is particularly useful for automatic centering of a cathode-ray tube in applications Where equal averaged currents on a continuous sampling basis do not indicate centering; e. g., Where it is desired to center a cathoderay tube pattern at some point other than that of its average valve.

Other uses of the circuit employing intermittent sampling of an electrical Wave to be stabilized are contemplated.

In the drawings,

Fig. 1 of the drawing is a circuit diagram with amplifiers illustrating one phase of the inventlon;

Fig. 2 of the drawing is a circuit diagram showing amplifiers in push-pull relationship illustrating another phase of the invention; and

Fig. 3 of the drawing is a circuit diagram showing electronic switching devices connected to the circuit of Fig. 1 illustrating a third embodiment of the invention.

Referring particularly to Fig. 1 of the drawing, there is provided a circuit comprising tubes ID and II connected together in a novel way with a load I2 and a stabilized direct current voltage source I3, respectively. Tube I 0 is an amplifier which has a grid I4 energized by signals from the input signal source I5 via coupling capacitor IS. A plate I! of tube II! is energized by a direct current voltage through the load I2 whose average current consumption it is desired to maintain constant. A cathode I 8 of this tube is maintained at a desired bias potential with respect to ground by a cathode resistor I9. A resistor 20 and capacitor 2| comprise a filter circuit connected between cathode I8 and a grid 22 of tube I I characterized as a control tube.

Control tube II has only direct current power applied to the same and its cathode 24 is energized by a reference voltage which is substantially constant supplied from the stabilized voltage source I3 connected to ground through impedances 25 and 26, the part of this voltage, 1. e., the voltage drop from point 21 to ground across impedance 26, being impressed upon this cathode. The value of impedance 25 is purposely made comparatively small in this embodiment to overcome the effects of any possible changes in the control tube current upon the output of the control tube II. A convenient load for the direct current polarized anode circuit of tube I I is shown as a resistor 28. Anode 23 is coupled back to the grid I I of the tube III through a feedback circuit in a degenerative manner for reasons which will soon become apparent. This feedback path comprises a resistor 30. The grid I4 is also shown normally biased through a resistor 3|.

In operation, let it be assumed that the load I2 represents the coil of a deflection yoke in a cathode-ray tube circuit. In such case, the Fig. 1 circuit would represent one-half of a push-pull sweep amplifier circuit. The sweep input might well be from a Selsyn appearing at the signal source I 5 and is applied to grid I4 of tube III which, in this specific application, would be a tetrode tube.

In actual practice, another amplifier might be placed ahead of the first amplifier II) but since a demonstration of the inventors concept is not dependent upon such an additional tube, it is left out of the following discussion.

The amplified sweep voltage appears on the plate I! of amplifier II]. This plate, as previously mentioned, may be directly connected to a magnetic deflection yoke of a cathode-ray tube. Actual deflection of the cathode-ray beam is proportional to the instantaneous current flowing through the deflection coil and not to the voltage appearing across it.

Neglecting screen current in the tube I0, now considered as a tetrode, which is a small fraction of the plate current of the tube, the voltage appearing across the cathode resistor I9 of tube Ii] may be taken as a measure of the instantaneous deflection coil current. This voltage is filtered by means of the filter elements 20, 2| to provide a direct current potential proportional to the average value of the yoke current, and is supplied to the grid of the control tube II. The cathode of tube II returns to a point of fixed potential, as described above. The plate voltage of the control tube is now seen to be a function of the difference between the reference voltage and the average potential of the cathode of tube I0 relative to ground. If the latter is high, the plate potential of the control tube will be low, and vice versa. The grid I I of the first tube is supplied, by a grid-leak resistor 3|, with negative voltage (as shown) and is further connected to the plate amplifiers. sidered amplifiers Ill and H of Fig. 1 for the purpose of convenience since the second pair.

rename? ".grid 14 of ithefirst tube in such a manneras to hold ,its average cathode potential to a value substantially equal to the reference voltage. This means'that the direct current component of deflection coil current is held constant.

For the purpose oi'developingthe invention to a high p'laneio'f usefulness, another circuit embodi- 'ment' as showninFig. 2 was considered necessary.

This circuit is really composed of two pairs-oi A first pair might as we'll be conila'beled l, H, is the same as the first pair.

" I-hese amplifiers In, H andlll, l l,'are cons'idered in Epairs because each tube in each pair is functionally dependent on the other in the present setup. Also, this decision ai'ds in concisely-claiming the present aspect of the invention. Amplifiers'll and I' may be designated first and second control tubes.

This Fig. 2 circuit, which is presently to be described, 'copes with the problem of centering automatically the sweep in a cathode-ray tube circuit or, in another sense, balancing the current in either the respective paired deflection yokes or deflecting elements of any electron beam deflecting indicator, and it is quite readily further "recognized that amplifier tubes Ill and Ill are coupled in'a push-pull arrangement with a load 40 which may comprise either a pair of coils or a single center-tapped coil for the deflection yokes associated with either the horizontal or vertical deflection of an electron beam in an indicator such as a cathode-ray tube. Also, the control tubes H and H are effectively connected in push-pull. If, for the moment being, the circuit associated with the stabilized voltage source It is not considered in the circuit of Fig. 1, it is seen that the circuit of Fig. 2 is in many respects a duplication of the elements of the first circuit, but further study will reveal other and pertinent additions to this disclosure. Those elements of l, which are, from a schematic viewpoint, duplicated in Fig, 2, are primed. Actually, the

resistors-and capacitors in this last circuit would undoubtedly have values materially different than in the first'instance.

25. Due to a grounded resistor 26 being connected to the cathode circuit of these tubes H, H at junction 21, it is evident that a relatively fixed reference voltage is continuousl present at cathodes 24 and 24 for the purpose described above in connection with Fig. 1.

Hence, it appears that in the subject circuit'as thevoltage on the grid of one control tube, such as tube H, increases in a positive direction, its anode current increases. This causes the volt agedropacross the cathode resistor 25 of thesame *amplifier to increase and hence, since the voltage on the grid 22' of the other direct currentamplifier H is the same as it was and resistor 26 is also connected to cathode 24', it is recognized'that the effective bias of tube II is made more negative, thus causing a decrease in current how in this tube. Thus, itfollows that when the average current'in one alternating current amplifier such as amplifier fllwgoes up, the action 0f the.zcontrol tubes II, II with the common cathode resistor 26 is to increase the 'biason'the alternating .current amplifier to bring the avera'ge current down in the load associatedwith this amplifierwliile, *at'the'same time, tube ll" decreases 'the'bias'on the other alternating current 'amplifier I 0 "to bring the average current up in the'corre'spon'ding load. Consequently, since the load is in a push-pull relation with the alternating current amplifiers and the particular-load chosen is the coils of'the deflection yokes of a'cathoderay tube, it can be stated that 'the'e'lectron beam is automatically centered on a fluorescent target each time the sweep voltage applied to the tube:pa'sses through its'average value, due to the factthat the described circuit makes it possible to retain the average deflection current in both coilsifor one plane of deflection in a balanced relationship. When the cathode impedance of the control-tubes is made very small, cathode potential variations, due 'tolplate current changes fromlany instability of the stabilized direct current voltage source l3, are relatively'very'small. Therefore, the balanced current condition aboveca'n be made a substantially constant'current setup.

This last circuit, as well as the Fig. l'circuit, eliminates the previously requiredseparatesweep centeringcircuit frombeing apart from "the 'deflection'circuit in cathode-ray tube circuits, 'Better fidelity of response is achieved' also-since an inductive coupling is not present in thedeflection yoke circuit. The last described circuit als'oovercomes variations in the characteristics of the amplifier tubes.

It will be understood that the circuit of Fig. 2 can be used equally well to provide a :pushpull audio-frequency amplifier in which the -direct current components of load current are-automatically maintained in substantial balance.

Another circuit embodiment of the inventors concept of stabilizing the current through a load is shown in Fig. 3, wherein stabilization takes place ona substantially instantaneous value basis. This will be made clear as the description of this circuit progresses hereinafter. However, in all embodiments of the invention, the problem of stabilizing a load current is solved irrespective of whether the sampling of the potential across the cathode load or bias for the power amplifier is done on a continuous or recurrent interval basis. Sampling as used in this specification means that at selected times or on a continuous time basis the voltages present across the cathode resistor I S are impressed on the averaging or filtering network 20, 2!, which in turn being connected to the input of the control tube ll causes this amplifier to "act as a control voltage generator.

Fundamentally, the circuit of Fig. -3 is 'thesame as that in Fig. 1 since the :power amplifiers and control tubes are organized with the filter or averaging circuit, the degenerative feedback circuit and the control tube reference or stabilized voltage means in the same manner. There- 'iore, these devices or elements arelabelled-alike a discharge device .53 such as a triode tube by a capacitor 52.

A resistor 59 connected in series with a diode tube 60 is interposed between the cathode l8 of device 10 and the averaging circuit 20, 2|. The anode 6| of diode tube 60 is connected to resistor 59, and its cathode 62 is connected to the filtering circuit 20, 2 I.

A resistor 5'! is connected between the grid 55 of the discharge device 53 and its cathode 56, so that the grid is normally biased slightly positive with respect to its cathode and the tube thus rendered normally conductive. The cathode 56 is connected to a source of constant negative potential as shown at 58. The output circuit of device 53 includes the resistor 59. Thus, when device 53 is conductive, as it normally is, there is a large potential drop across the resistor 59, so that the anode (ii of the diode tube 60 is negative with respect to its cathode B2, rendering diode tube 60 nonconductive. Accordingly, no current flows to charge the capacitor 2|.

Generator is arranged in a well-known manner to develop a negative voltage pulse at the instant the signal wave applied to the grid I 4 of the power amplifier I0 is passing through zero. The application of this negative pulse to the grid of the device 53 renders the latter nonconductive, so that there is no appreciable potential drop across the resistor 59. Under these conditions, the anode 6| of diode tube is positive with respect to its cathode 62, and a current flows until the capacitor 2| is charged substantially to the potential of the cathode I 8.

At the end of each negative pulse from generator 50, the device 53 again becomes conductive, producing a potential drop across the resistor 59 and rendering the anode 6| of the diode tube 60 negative with respect to its cathode 62. Thus diode tube 50 is nonconductive so that the charge.

upon the capacitor 2! is unable to escape through the diode and the now-conducting device 53. The charge upon the capacitor 2|, therefore, decays slowly through resistor 20. It will thus be apparent that the grid 22 of the device H is maintained at an average potential which is dependent upon the potential of the cathode [8 at the instant when generator 50 produces a negative voltage pulse.

The resistor 59 has a high resistance value compared with that of the resistor IS. The resistor 59, for example, may have a resistance of 50,000 ohms and the resistor IS a resistance of 1,000 ohms. The effective resistance in the cathode circuit of the device l0, therefore, does not change appreciably as the device 53 is alternately rendered conductive and nonconductive. Accordingly, the sampling process has a negligible effect upon the normal performance of the device Ill.

The remainder of the circuit in Fig. 3 from this point operates as it did in the Fig. 1 embodiment. The discharge of capacitor 2| through resistor 20 in the interval between pulses or discharge cycles of tube 50 is made negligible. Hence, it is recognized that sampling of the load current including both alternating and varying direct current waves applied to the load is done on an intermittent or recurrent basis, and due to the fact that the sampling or impressing of the cathode voltage of the power amplifier [0 upon the averaging network 20, 2! is synchronized with the signal wave applied to the grid of this same amplifier Iii, the maintaining of the average current through the load constant is effectively done on an instantaneous value basis.

A significant value of this last embodiment shown in Fig. 3 resides in the fact that when it is expanded to cover push-pull operation, exemplified in the cathode-ray tube application shown in Fig. 2, the resultin circuit can be used for the purpose of keeping the instantaneous current through the magnetic yokes of this tube equal at a predetermined instant of sweep voltage. The full disclosure of the Fig. 2 circuit taken with that in the circuit of Fig. 3 is sulficient to cover the case of push-pull operation of the latter circuit.

Since many changes could be made in the above construction and many apparently widely different embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is: 7

1. In a current stabilizing circuit, the combination of a first electron discharge tube having an anode, cathode and control grid; means for supplying an intermittent signal wave to the control grid of said tube; anode and cathode loads coupled to said tube; an averaging circuit; means for applying a cathode potential of said firs-t discharge tube to said averaging circuit at least for a portion of each cycle of said signal wave whereby an averaged potential is obtained; means for providing a reference potential; a second electron discharge tube responsive to the difference between said reference potential and said average potential for generating a control potential; and means for altering the potential on the grid of said first discharge tube in response to said control potential whereby the average current through said anode load remains substantially constant during said portion of each cycle of said signal wave.

2. In a current stabilizing circuit, the combination of a first electron discharge tube having an anode, cathode and control grid, means for supplying a recurrent signal wave to the control grid of said tube, anode and cathode loads coupled to said tube, means for sampling the potential across said cathode load at least during predetermined recurrent portions of said signal wave, means for averaging the sampled potential, means for providing a reference potential, a second electron discharge tube responsive to the difference between said reference potential and said average sampled potential for generating a control potential, and means for altering the potential on the grid of said first discharge tube in response to said control potential whereby the average current through said anode load remains substantially constant at least during the predetermined portions of said signal wave.

3. In a current stabilizing circuit, the combination of a plurality of amplifiers each having a cathode, control grid, and anode; a signal input source having a predetermined frequency applied to the grid of a first amplifier; a load attached to the anode of said first amplifier; means including a stabilized voltage source for impressing a fixed reference voltage to the cathode of a second amplifier; means including a filter circuit interposed between the cathode of said first amplifier and the grid of said second amplifier for sampling at least on said predetermined frequency basis the cathode voltage of said first amplifier whereby voltage proportional to the difference between said reference voltage and the filtered cathodevoltage of the first ,amplifierdependent. upon the sampled portionof the load current is made the effective grid bias of the second amplifier; and a degenerativefeedback circuit interposed between the anode of said second amplifier and thegridofsaid first. amplifier, whereby the amplified gridbias changes of said second amplifier fed to the grid of saidfirst amplifier serve to stabilize the current through, said load.

4. In a currentstabilizing circuit, the combinationof a plurality of, amplifiers each having a cathode, a control grid,,and anode; a signalinput source to the grid of afirst amplifier; a load attached tothe anode of said; first amplifier; means for supplying a fixed. reference voltage to the cathode of a second amplifier; means including a filter circuit interposedbetween the cathode of said first amplifier and the grid of said second amplifier for sampling; at least on a recurrent basis dependent on saidsignal input the cathode voltage of said first amplifier whereby voltage proportional to the difference between said reference, voltage and the filtered cathode voltage of the first amplifier dependent upon the direct current portion of the sampled load current is made the efiective gridbias of thesecond amplifier; and a degenerative feedback circuit interposed between the anode of said second amplifier and.

the gridof said first amplifier, whereby the amplified grid bias changes of said second amplifier fed: to. the grid of said first amplifier serve to stabilize thecurrent through said load.

5. In a circuit for maintaining a constant current to. a load, the combination comprising an alternating current amplifier and a direct current amplifier, each.having at least a cathode, control grid; andanode; a signal input source to the grid, of, thealternating current amplifier; a load coupled to the anode of said alternating current amplifier; means for impressing a stable voltage to the cathodeof the direct current amplifier; means interposed between the cathode of said alternating current amplifier and the grid of said direct current amplifier whereby voltage proportional to the difference between said stable voltage and a direct current voltage component of the alternating current amplifier cathodevoltage, dependent upon the average load current is made the efiective grid biasof the direct current amplifier; and a degenerative feedback circuit interposed between the alternating current amplifier; grid and direct current amplifier anode, whereby the amplified grid bias changes of said direct; current amplifier fed to said grid of the alternating current amplifier serve to maintain the current constant through said load.

6; In a. current balancing circuit, the combination of; a plurality of amplifiers, each having a cathode, control grid, and anode; a variable input source to a first amplifier; a load attached to the anode of said first amplifier; mean including a filter circuit between the cathode of said first amplifier and the input of said second amplifier; means including a stabilized voltage source for impressing a fixed reference voltage to the oathode of said second amplifier; an inverse feedback circuit from the anode of said second amplifier to theinputcircuit of said first amplifier, whereby average current changesl in said load indicated by proportional changes in the cathode potential of the first amplifier is fed back after amplification by said-second amplifier to, the input of said first amplifier out or phase with an. original input signal to produce a balanced load current.

7'. In: a current stabilizing, circuit, the combie nation ofa plurality of amplifiers each havin a cathode, control grid, an anode; a signal input, source to the grid of a first amplifier; aloadate tached to the anode of said first amplifier; means including a stabilized voltage source for impress ing a fixed reference voltage to the cathode of a second amplifierj, means including afilter circuit interposedbetween the cathode of said; first am plifier and the grid of said second amplifier whereby voltage proportional to the difierence between said reference voltage and the filtered cathode voltage of the first amplifier dependent upon the average load current is made the efiec tive grid-bias ofv the second amplifier; and a dc generative feedback circuit interposed between; the anode of said second amplifier and the grid of said first amplifier, whereby the amplified grid bias changes of said second amplifier fed to1th6, grid of said first amplifier serve to stabilize the, current through said lead.

8. In a. current balancing circuit for; use wit-ha cathodeeray: tube including a pair of series con; nected deflection yokes for each beam axis; the, combination comprising two pairs of amplifiers each having a cathode, control grid and anodoia common input source to the grid of a first plifier in each pair, the first amplifiers beingeom nected in push-pull; said pair of defiectionyokes being interposed between the plates or saidfirst amplifiers; means including a stabilized voltage source for impressing a fixedreference voltage to the cathode of a second amplifier in each pair, the second amplifiers being connected in push-pull so thatv variations in the reference voltagecan have no effect on the circuit; means including filter circuits interposed between the cathode of said first amplifiers and the grid of said second ame plifier in each pair whereby a voltage proportional. to the difference between said reference voltage; and'saidfiltered'cathode voltage dependent upon the average loadcurrent through said-pair ofrdee fiectionyokes iszmade the efiective grid biasaofsaid. second amplifiers;: and degenerative feed.- backcircuits interposed betweenthe anode of said second amplifier andthe grid of; saidfirstaamplh fierof each pair, whereby'the amplified grid-bias changes of saidsecond amplifiers fed to said grids, serve tobalance the respective current in eachofi saidyokes for the automatic centering, of an elec? tron beam of said1cathode-ray tube.

9. In a current balancing circuit, the combination of. a pair of: series connected loads; a signal; source of predetermined frequency coupled; to saidiload's; two, pairs of amplifiers each havin la. cathode;,cdntrol gridand anode; a commoninput:

sourceto the grid of afirst amplifier in each pair the first: amplifiersbeing connected in push-pull; said pair of loads being interposed betweenthe plateslof said first amplifiers; means for supply, ing. afixed'reierenccvoltage to the cathode of'a second amplifier in; each pair, the second; amplifiers beingjoonnected in push-pullsothat varia-. tions in the reference voltagecarr have no effect, on the circuit; means including filter circuitsinterposedbetweemthe cathode of said first amplifiers andithe gridzof saidsecond amplifier ineach, pair for. sampling atzleast onsaid predetermined; frequency basis the cathode voltage of saidfirst amplifier'whereby a voltage proportionalzto the difference between said reference voltage and said filtered cathode, voltage dependent upon the sampled portionof the load current throughsaid pair of'loads is made the eifective grid bias of said. second; amplifiers; and degenerative feedback cilicuitsiinterposedbetween the anode of saidsecond,

amplifier and the grid of said first amplifier of each pair, whereby the amplified grid bias changes of said second amplifiers fed to said grids serve to balance the respective current in each of said loads.

10. In a current balancing circuit for use with a cathode-ray tube including a pair of series connected deflection yokes for each beam axis, the combination comprising a plurality of amplifiers, each having a cathode, control grid and anode; a common signal input source connected to the grids of a first amplifier and a second amplifier connected in push-pull; said pair of deflection yokes being interposed between the plates of said first and second amplifiers; means including a stabilized voltage source for impressing a fixed reference voltage to the cathode of a third amplifier and a fourth amplifier; means including filter circuits, one being interposed between the cathode of said first amplifier and the grid of said third amplifier, the other of said last means being interposed between the cathode of said second amplifier and the grid of said fourth amplifier, whereby a voltage proportional to the difference between said reference voltage and the filtered cathode voltage of said first and second amplifiers dependent upon the average load current through said pair of deflection yokes is made the effective grid bias of the third and fourth amplifiers; and degenerative feedback circuits, one being interposed between the anode of said third amplifier and said grid of said first amplifier, the other being interposedbetween the anode of said fourth amplifier and said grid of said second amplifier, whereby the amplified grid bias changes of said third and fourth amplifiers fed to said grids serve to balance the respective current in each said yokes for the automatic centering of an electron beam of said cathode-ray tube.

11. In a current balancing circuit for use with a cathode-ray tube including a pair of series connected deflection yokes for each beam axis, the combination comprising a plurality of amplifiers, each having a cathode, control grid and anode; a common signal input source connected to the grids of a first alternating current amplifier and a second alternating current amplifier connected in push-pull; said pair of deflection yokes being interposed between the plates of said first and second alternating current amplifiers; means including a stabilized voltage sourc for impressing a fixed reference voltage to the cathode of a direct current third amplifier and a direct current fourth amplifier; means including filter circuits, one being interposed between the cathode of said first alternating current amplifier and the grid of said direct current third amplifier, the other of said last means being interposed between the cathode of said second alternating current amplifier and the grid of said direct current fourth amplifier, whereby a voltage proportional to the difference between aid reference voltage and the filtered cathode voltage of said first and second alternating current amplifiers dependent upon the average load current through said pair of defiection yokes is made the effective grid bias of the direct current third and fourth amplifiers; and degenerative feedback circuits, one being interposed between the anode of said direct current third amplifier and said grid of said first alternating current amplifier, the other being interposed between the anode of said direct current fourth amplifier and said grid of said second alternating current amplifier, whereby the amplified grid bias changes of said direct current third and fourth amplifiers fed to said grids serve to balance the respective current in each said yokes for the automatic centering of an electron beam of said cathode-ray tube.

12. In a current balancing circuit for use with a cathode-ray tube including a pair of series connected deflection yokes for each beam axis, the combination comprising a plurality of amplifiers, each having a cathode, control grid and anode; a common signal input source connected to the grids of a first amplifier and a second amplifier connected in push-pull; said pair of deflection yokes being interposed between the plates of said first and second amplifiers; means including a stabilized voltage source for impressing a fixed reference voltage to the cathode of a third amplifier and a fourth amplifier; means including filter circuits, one being interposed between the cathode of said first amplifier and the grid of said third amplifier, the other of said first means being interposed between the cathode of said second amplifier and the grid of said fourth amplifier, whereby a voltage proportional to the difference between said reference voltage and the filtered cathode voltage of said first and second amplifiers dependent upon the average load current through said pair of deflection yokes is made the effective grid bias of the third and fourth amplifiers; and degenerative feedback circuits, one being interposed between the anode of said third amplifier and said grid of said first amplifier, the other being interposed between the anode of said fourth amplifier and said grid of said second amplifier, whereby the amplified grid bias changes of said third and fourth amplifiers fed to said grids serve to balance th respective current in each said yokes for the automatic centering of an electron beam of said cathode-ray tube.

13. In a current stabilizing circuit, the combi nation of a plurality of amplifiers each having a cathode, control grid, and anode; a signal input source to the grid of a first amplifier; a load attached to the anode of said first amplifier; means including a stabilized voltage source for impressing a fixed reference voltage to the cathode of a second amplifier; a resistor interposed between said last cathode and ground, means including a filter circuit interposed between the cathode of said first amplifier and the grid of said second amplifier whereby voltage proportional to the difference between said reference voltage and the filtered cathode voltage of the first amplifier dependent upon the average load current is made the effective grid bias of the second amplifier; and a degenerative feedback circuit interposed :between the anode of said second amplifier and the grid of said first amplifier, whereby the amplified grid bias changes of said second amplifier fed to the grid of said first amplifier serve to stabilize the current through said load.

14. In a, current stabilizing circuit, th combination of a plurality of amplifiers each having a cathode, control grid, and anode; a signal input source to the grid of a first amplifier; a load at tached to the anode of said first amplifier; means including a stabilized voltage source fed to ground through a tapped resistor for impressing a fixed reference voltage to the cathode of a second amplifier; a resistor interposed between said last cathode and ground; means including a filter circuit interposed between the cathode of said first amplifier and the grid of said second amplifier whereby voltage proportional to the difference between said reference voltage and the filtered' cathode voltage of the first amplifier dependent upon the average load current is made the effective grid bias of the second amplifier; and a degenerative feedback circuit interposed between the anode of said second amplifier and the grid of said first amplifier; whereby the amplified grid bias changes of said second amplifier fed to the grid of said first amplifier serve to stabilize the current through said load.

15. In a current stabilizing circuit, the combination of a plurality of amplifiers each having a cathode, control grid, and anode; a signal input source to the grid of a first amplifier; a load attached to the anode of said first amplifier; means including a stabilized Voltage source fed to ground through a tapped resistor for impressing a fixed reference voltage to the cathode of a second amplifier; a resistor interposed between said last cathode and ground; means including a filter circuit interposed between the cathode of said first amplifier and the grid of said second amplifier whereby voltage proportional to the difference between said reference voltage and the filtered cathode voltage of the first amplifier dependent upon the average load current is made the effective grid bias of the second amplifier; a load connected to the anode of said second amplifier; and a degenerative feedback circuit interposed between the anode of said second amplifier and the grid of said first amplifier, whereby the amplified grid bias changes of said second amplifier fed to the grid of said first amplifier serve to stabilize the current through said load.

16. In a current stabilizing circuit, the combination of a plurality of amplifiers each having a cathode, control grid, and anode; a signal input source to the grid of a first amplifier; a load attached to the anode of said first amplifier; means including a stabilized voltage source for impressing a fixed reference voltage to the oathode of a second amplifier; a resistor interposed between said last cathode and ground; means including a filter circuit interposed between the cathode of said first amplifier and the grid of said second amplifier whereby voltage proportional to the difference between said reference voltage and the filtered cathode voltage of the first amplifier dependent upon the average load current is made the effective grid bias of the second amplifier; a load connected to the anode of said second amplifier; and a degenerative feedback circuit interposed between the anode of said second amplifier and the grid of said first amplifier, whereby the amplified grid bias changes of said second amplifier fed to the grid of said first amplifier serve to stabilize the current through said load.

1'7. In a current stabilizing circuit, the combination of a plurality of amplifiers each having a cathode, control grid, and anode; a signal input source to the grid of a first amplifier; a load attached to the anode of said first amplifier; means including a stabilized voltage source fed to ground through a tapped resistor for impressing a fixed reference voltage to the cathode of a second amplifier; means including a filter circuit interposed between the cathode of said first amplifier and the grid of said second amplifier whereby voltage proportional to the difference between said reference voltage and the filtered cathode voltage of the first amplifier dependent upon the average load current is made the effective grid bias of the second amplifier, a load connected to the anode of said second amplifier; and a degenerative feedback circuit interposed between the anode of said second: amplifier andthe':

grid. of said first amplifier, whereby the amplifled grid bias, changes of said second amplifier fed to the grid. of said first amplifier serve to.

stabilize the current through said load.

18. In a current stabilizing circuit, the combination of a plurality of amplifiers each having a cathode, control grid, and anode; a signal. input source to the grid of a first amplifier; a load attached to the anode of said first amplifier; means i including a stabilized voltage source fed to.

ground through a tapped resistor for impressing a, fixed: reference voltage to the cathode of a second amplifier; means including a filter circuit interposed between the cathode of said first amplifier and the grid of said second amplifierwher-eby voltage proportional to the differencebetween said reference voltage and the filtered cathode voltage of the first amplifier dependent upon the average load current is made the effective grid bias of the second amplifier; and a degenerative feedback circuit interposed between the anode of said second amplifier and the grid of said first amplifier, whereby the amplified grid bias changes of said second amplifier fed to the grid of said first amplifier serve to stabilize the current through said load.

19. In a current balancing circuit for use with a cathode-ray tube including a pair of series connected deflection yokes for each beam axis, comprising a plurality of amplifiers, each having a cathode, a control grid and anode; a common signal input source connected to the grids of a first alternating current amplifier and a second alternating current amplifier connected in push-pull; said pair of deflection yokes being interposed between the plates of said first and second alternating current amplifiers; means including a stabilized voltage source for impressing a fixed reference voltage to the cathode of a third direct current amplifier and a fourth direct current amplifier; means including filter circuits, one being interposed between the cathode of said first alternating current amplifier and the grid of said third direct current amplifier, the other of said last means being interposed between the cathode of said second alternating current amplifier and the grid of said fourth direct current amplifier, whereby a voltage proportional to the difference between said reference voltage and the filtered cathode voltage of said first and second alternating current amplifiers dependent upon the average load current through said pair of deflection yokes is made the effective grid bias of the third and fourth alternating current amplifiers; and degeneratve feedback circuits, one being interposed between the anode of said third direct current amplifier and said grid of said first alternating current amplifier, the other being interposed between the anode of said fourth direct current amplifier and said grid of said second direct current amplifier, whereby the amplified grid bias changes of said third and fourth direct current amplifiers fed to said grids serve to balance the respective current in each said yokes for the automatic centering of an electron beam of said cathode-ray tube.

20. In a current balancing circuit for use with a cathode-ray tube including a pair of series connected deflection devices for each beam axis the combination comprising a pluralit of amplifiers, each having a cathode, control grid and anode; a common signal input source connected to the grids of a first alternating current amplifier and a second alternating current amplifier connected 15 in push-pull: said pair of deflection devices being interposed between the plates of said first and second alternating current amplifiers; means including a stabilized voltage source for impressing a fixed reference voltage to the cathode of a third direct current amplifier and a fourth direct current amplifier; means including filter circuits, one being interposed between the cathode of said first alternating current amplifier and the grid of said third direct current amplifier, the other of said last means being interposed between the cathode of said second alternating current amplifier and the grid of said fourth direct current amplifier, whereby a voltage proportional to the difierence between said reference voltage and the filtered cathode voltage of said first and second alternating current amplifiers dependent upon the average load current through said pair of deflection devices is made the efiective grid bias of the third and fourth alternating current amplifiers; and degenerative feedback circuits, one being interposed between the anode of said third direct current amplifier and said grid of said first alternating current amplifier, the other being interposed between the anode of said fourth direct current amplifier and said grid of said second direct current amplifier, whereby the amplified grid bias changes of said third and fourth direct current amplifiers fed to said grids serve to balance the respective current in each said devices for the automatic centering of an electron beam of said cathode-ray tube.

DAVID E. KENYON.

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