US2391862A - Electrical circuit arrangement - Google Patents

Description

Jan. l, 1946. H. G. BOYLE ELECTRICAL CIRCUIT ARRANGEMENT Filed Oct. l, 1942 @www NN 'BY www ATTRNEY Patented Jan. 1, 1946 2,391,862 ELECTRICAL CIRCUIT ARRANGEMENT Homer G. Boyle, Dobbs Ferry, N. Y., assigner to Hartford National Bank and Trust Company, Hartford, Conn., as trustee Application October 1, 1942, Serial No. 460,447

3 Claims.

The present invention relates to electrical circuit arrangements and more particularly to circuit arrangements for operating cathode-ray discharge tubes in which the position and/or displacement of an electron beam is controlled by applying varying voltages to one or more sets of electron-beam deecting electrodes.

The circuit arrangements of the invention are particularly suitable for energizing the deiiecting electrodes of cathode-ray tubes suitable for television purposes and in which the control or signalling voltages having generally a saw-tooth form, embody an extensive frequency range extending from the fundamental frequency of the saw-tooth wave to frequencies of the order of fifty megaoycles or more.

It is an object of the invention to provide an improved circuit arrangement for energizing the deecting electrodes of cathode-ray tubes.

Another object of the invention is to provide a coupling amplifier circuit for cathode-ray tubes which circuit is characterized by a high degree of stability, a uniform amplification over an eX- tended frequency range and by a minimum of harmonic and phase distortion and which at the same time is simple and requires a minimum of components.

These and further objects of the invention will appear as the specification progresses.

The circuit arrangement in accordance with the invention comprises a push-pull voltage amplifier having output electrodes connected in symmetrical relationship to the deflecting electrodes of the cathode-ray tube and comprising a degenerative phase-inversion network which provides at the output of each branch of the amplier signalling voltages for the deflecting electrodes which are mirror images of each other with respect to both amplitude and phase and which network simultaneously makes possible the control of the dynamic position of the electron beam pattern of the cathode-ray tube. In accordance with a preferred embodiment of the invention the output electrodes of the push-pull voltage amplifier are directly connected to the denecting electrodes of the cathode-ray tube whereby a maximum voltage transfer efliciency between these elements is obtained.

A further feature of the invention is a novel circuit arrangement by which the operating potentials for the cathode-ray tube and its associated amplifier are supplied by low and high voltage sources in series and arranged in such manner that the low voltage components of the amplier are shielded from the high voltage source.

Referring to the drawing, there is shown a cathode-ray tube I0 comprising within an envelope I I an electron-emitting cathode electrode I2, a control electrode I3, and focusing electrodes I4 and I5 for producing an electron beam. For deiiecting the electron beam in a horizontal and vertical manner there are provided horizontal deflecting electrodes IS-IB and vertical deflecting electrodes I1-I1, The construction and arrangement of electrodes I2 to I'I inclusive is Well kno-Wn to those skilled in the art and a further description of the same is believed to be unnecessary.

Connected across beam forming electrodes I2, I3, I4 and I5 is a resistor network comprising series connected potentiometer resistors and 4I. The free end of resistor 49 is connected to the grid electrode I3 through a grid leak resistor 42 and to the negative pole of the voltage supply later to be described, Whereas the free end of resistor 4I is connected to the electrode I5 and to a ground conductor 58.

Cathode I2 is connected to the adjustable tap of resistor 4i) and focusing electrode I4 is connected to the `adjustable tap of resistor 4I whereby adjustment of the intensity of the electron beam respectively proper focusing of the electron beam is obtained by adjusting the positions of the respective tappings. In accordance with the known practice in the television art a modulating voltage may be applied to the control grid I3, for example, from an external source (not shown), Said source also including automatic background control devices of the usual type.

Horizontal deflecting electrodes IG-I are energized from a push-pull voltage amplifier comprising a valve 20 having cathode, grid and anode electrodes 20a, 2Gb and 20c respectively,

and a valve 2| having cathode, grid and anode i electrodes 2Ia, 2lb and 2Ic respectively. As shown in the drawing and in accordance with the invention, the anodes 20c and 2Ic are directly connected to the deflecting electrodes Iii-I6.

interconnecting the anodes 20c and 2Ic is a potentiometer resistor 22 the adjustable tapping of which is connected to avoltage supply conductor 23 through a resistor 24. Potentiometer 22 and resistor 24 in combination constitute the output resistors of the valves 2U and 2I whereby the output resistor of valve 20 comprises the resistor 24 in series with that portion of the potentiometer 22 contained between the tapping and the anode 20c. Similarly, the output re Grid electrode h is energized by a suitable source orhorizontal deiieotion signalling, voltage for example, a saw tooth waveA generator (not shown) to which the grid 20h is connected in conventional manner. Grid electrode. 2lb, is.

energized by the differential voltage degenerae tively developed across resistor 24 to which the grid; electrode is connected; through a blocking condenser 26. Grid leak resistors 25 and 2` provide; a, direct current path to;` the groundl conductor- 58 for the grid; electrodes; 20h and` 2lb respectively. y

When-thefvalvesf20 and 21 havea substantially highV amplificationf-actoriA the cathodes. 20a and 2 |v are interconnected and returned directly to the.: ground conductor- 5-1 in; which, casezsuf.- ficient bias voltage for operating* the valvesy is obtained: by.- gridiirectification of? the; signallingV voltage.Y However, when the valves 2li-2| haveA a low ain-nlificationv factorf'l prefer; to provide other: sources@ of; bias voltage for: example a cathode bias resistor 23 which is interposed be` tweenL the; cathodes 2cd-ldlcL and the. ground conductor 58. A1. condenser 2,9,y connectedlacross the; resistor.' 28;. serves as; a low.'y impedanceshunt forthei Signalling currents transmitted through theamplier;

The voltages for energizing., the. vertical deiiectingiplates|1n arederived from. a push-A pullV amplier; similar to that.` above described and comprising a valve V having cathode, grid and" anode; electrodes` 3mi; 30h, and 30ev respectively andi a valve 3| having:` cathode, gridi and; anodegelectrodes-Sglai 3|b and 3|'crespectively.l Anodes- 30o and;r 31e are directly connected to their respective deecting electrodes Il -IT and are interconnected, byl aY potentiometer resistor Methan-lovable taproi whichlis connected to the supplyr conductor' 23: through a resistor' 34:

Grid electrode 30b1is energizedVv from anexternalsource of vertical deiiectionV signalling voltage (not shownl., In instancesI Where the cathode-ray tube is to.y be used for' television purposes, said source may; be asavv-tooth` wave generator whereas in the case where. V-the cathode-ray tubeY isto bei used as anioscilloscope or similarfvisuall indicator the source comprises the generatorof theVv voltage to be observed.v Grid electrode Sib is`4 energized'- by the; cliler-A ential voltage degenerativelydeveloped across theY resistor 34 to which the grid. is connected.; througha blockingcondenser'. Grid leaks 35" and 31` provide direct current paths tothe groundiconductor 58 for the', grid. electrodes 30h and alb, respectively. Biasfvoltagegfor the valves 30-3i|fisprovided by a' cathode resistor 38 interposed betWeencathodesl-30a.3la and therground :onductor4 5.8i A` condenser 39s connected' across resistor 38 serves kas a lowA impedance shuntv formev signalling currents transmitted, through the tmplifier.

The operating: potentials for the amplifiers 20-2I and 30-3I and for cathode-ray tube |10 are derived from a transformer having a primary winding 5l and secondary windings 52 and 53. Winding 52 is connected in full-wave 5 rectifying arrangement to produce a comparatively low direct `voltage (i. e. 350 volts) and for this purpose the ends 54-54 of the winding are connected to anodes, 5Fl-55. of a= rectier valve 56. A center-tapping` 5l of the winding connected to the ground conductor 58 serves as the direct current return and as the negative pole of the voltage supply. The positive pole oi the voltagey supply is taken from cathodes Filis- 59 of the valve 56` to which the supply conductor 23 ,is,connect'ed with the interposition of a low-passlter comprising a choke inductance 6e and filter condensers 6| and 62.

`Winding 5,3: is connected in half-wave rectifyingVv arrangement to produce a comparatively high direct voltage (i. e. 1000 volts) said windingjhaving one end` connected tov thev free end. of resistor dthrough a conductor 'Hl serving asthe negativefpole'of theyvoltage supply. The other end of winding' is connectedto the anodeA (i5V of a rectifier valve 63 the cathodeof which islconnected to the ground conductor 5B serving as the positive pole. of the voltage supply. A condenser 64 connected across the conductors 58 and 'I0/serves forsmoothing the; rectified voltage derivedfrom the rectier valve; 63.

It will be seen that by means of the:- circuit arrangement aboveV described in which. the anodes or the, amplifier valves are directlyy con: nected to/ thedeflecting electrodes a maximum. transfer efficiency betweenthe amplier andthe defiecting electrodes is obtained at all. frequen`v cies atwhichA thecathode-ray tube can be used and thenfull. value of! they voltages, appearing at the anodesis impressed on theI deflecting electrodcs. Moieoven sincethestray capacities of the output circuit or theL amplifiers are greatly reduced, frequency discrimination, non-linearity and other forms: ofi distortion likewise are reduced` toga low value. Furthermore,r becausevof 45-the degenerative feed-back coupling to which each ofthe ampliers is subjectedby the phaseinversion networks for energizing the valves- 2| and 3|, the above distortions are further minimized.

An important advantage of the circuit abovev described isthat the'tappings of the degenerative feed-back networks being adjustable make it possible to obtain both phase and voltage balance of the amplifiers and to` simultaneously neutralize or counterbalance substantially entirely the effects ofl unpredictable residual' stray capacities introduced by the ainplier tubes', the cathode-ray tube and the interconnecting wiring.

A further advantage arises from the unique manner-in which the low-voltage supplyand the high-voltager supply are interconnected which perli'iit's the necessary high voltages to be applied tothe elements of theV cathode-ray tube I0 without subjecting the amplifier valves 20-2I` and Sr-3 I `to a voltage in exoessof that obtained from the low voltage supply notwithstanding the direct interconnection between the cathode-ray tubeand the anodes of` the amplifier valves.

It should: bewell understood that while the invention. hasv been illustrated withv amplier valves-202|f and 3|l-3IY of thetriode type, the invention is equally applicable to amplifier valves of theA tetrodc, pentode or other multi-grid con- 75 struction,

While I have described my invention in a specic embodiment and by means of a specic example, I do not wish to be limited thereto for obvious modifications will occur to those skilled in the art without departing from the spirit and scope of the invention.

What I claim is:

1. In a circuit arrangement in combination, a cathode-ray tube comprising electron-beam producing elements and a pair of deecting electrodes for displacing said beam, and a voltage amplier for applying signalling currents to said delecting electrodes, said amplifier comprising two discharge valves having grid and anode electrodes connected in push-pull arrangement, an impedance element having its end portions interconnecting Vthe anodes, a second impedance element common to both valves and interposed between an adjustable tapping of said rst impedance element and a point of low-signalling current intensity, means to apply signalling currents to the grid electrode of one of said valves, and means comprising an interconnection between said tapping and the grid electrode of the other valve for applying signalling currents to said latter grid electrode in phase opposition to the signalling currents applied to the grid electrode of the first of said valves.

2. In a circuit arrangement in combination, a cathode-ray tube comprising electron-beam producing elements and a pair of deflecting electrodes for displacing said beam, a voltage amplier for applying signalling currents to said deflecting electrodes and a voltage source for energizing said amplifier, said amplier comprising two discharge valves having grid and anode electrodes connected in push-pull arrangement with the anode electrodes directly connected to said deflecting electrodes, a resistor element having its end portions interconnecting the anodes, a second resistor element common to both valves and interconnecting said voltage source and an adjustable tapping of said first resistor element, means to apply signalling currents to the grid electrode of one of said valves and means comprising an interconnection between said tapping and the grid electrode of the other valve for applying signalling currents to said latter grid electrode in phase opposition to the signalling currents applied to the grid electrode of the rst of said valves.

3. In a circuit arrangement in combination, a cathode-ray tube comprising electron beam producing elements including a cathode and an anode and a pair of deflecting electrodes for displacing said beam, a voltage amplifier for applying signalling currents to said deflecting electrodes, a voltage source for energizing said cathode-ray tube, a voltage source for energizing said amplifier, said amplifier comprising two discharge valves having grid and anode electrodes connected'in push-pull arrangement with the anode electrodes directly connected to said delecting electrodes, a resistor element having its end portions interconnecting the anodes, a second resistor element interconnecting the said amplifier energizing voltage source and an adjustable tapping of said rst resistor element, means to apply signalling currents to the grid electrode of one of said valves, and means comprising an interconnection between said tapping and the grid electrode of the other valve for applying signalling currents to said latter grid electrode in phase opposition to the signalling currents applied to the grid electrode of the first of said valves, the voltage source for energizing the cathode-ray tube having its negative pole connected to the cathode of the cathoderay tube and its positive pole connected to the anode of the cathode-ray tube and the voltage source for energizing the amplifier having its negative pole connected to the positive pole of said first voltage source and having its positive pole connected to the anodes of the said amplifier valves and the deilecting electrodes through said second resistor element.

HOMER G. BOYLE.

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