US1954779A - Electron tube system - Google Patents

Description

A ril 10, 1934. a. J. KELLEY ELECTRON TUBE SYSTEM Filed May 12, 1930 5 Sheets-Sheet l Flat p 193% G. J. KELLEY 1,954,779

ELECTRON TUBE SYSTEM Filed May 12, 1930 5 Sheets-Sheet 2 April 10, 1934. G. J. KELLEY 1,954,779

ELECTRON TUBE SYSTEM Filed May 12, 1930 5 Sheets-Sheet 3 p Svvoemtoz 6/ 6278/1/60 J fizzzff April 10, 1934. 5 KELLEY 1,954,779

ELECTRON TUBE SYSTEM April 1934- G. J. KELLEY 1,954,779

ELECTRON TUBE SYSTEM Filed May 12, 1930 5 Sheets-Sheet 5 W/ r/vass WOW? E %%%W Patented Apr. l0, 1934 U STATES ELECTRON TUBE SYSTEM Delaware Application May 12, 1930, Serial No. 451,562

11 Claims.

The present invention relates to electron tube systems, and is a continuation in part of my copending application Serial No. 429,956, filed February 20, 1930.

An object of my invention is the control of signal current effects within a direct coupled tube system so as to produce a high order of radio or audio frequency amplification throughout the system.

Another object of my invention is to so regu late and apportion the signal current effects with respect to direct current effects that abnormally high coefficients of amplification may be obtained, while maintaining faithful reproduction of the signals to be amplified.

Other objects of my invention will become apparent as the description of my invention is developed with reference to the accompanying .drawings in which modification of the direct coupled tube system of Fig. 1,

Fig. 4. diagrammatically illustrates a modification of the circuit arrangement of Fig. 3 and involves certain humbucking features,

Fig. 5 diagrammatically illustrates a modification of the energization system of Fig. 1,

Fig. 6 diagrammatically illustrates a modification of the circuit arrangement of Fig. 5,

Fig. 7 diagrammatically illustrates a modification of the energization and signal current system of Fig. 6,

Fig. 8 diagrammatically illustrates a modification of the energization and signal current system of Fig. 12 of my copending application here inbefore referred to,

Fig. 9 diagrammatically illustrates a modification of the circuit arrangement of Fig. 4, and

Fig. 10 diagrammatically illustrates the circuit arrangement of a complete radio receiving system embodying certain of the features disclosed in my copending application hereinbefore referred to in combination with certain of the features described with reference to the foregoing figures. i

Referring to Fig. l, VT1 and VT2 designate two electron tubes in direct coupled cascade relation having a signal input circuit SI andan output circuit which may consist of an output transformer OT and a loud speaking device LS. or other type of indicator. The input'circult may consist of any type of instrumentality developing an alternating current potential or fluctuat ing direct current potential.

VT1 and VT2 are four element and three element electron tubes respectively the cathodes of v which are energized through heating current transformers HTi and I-ITz. The plate of thetube VTZ is connected through a filter choke coil FCh to the positive terminal P of arectifier system including a rectifier tube RT energized from a power transformer PT. The cathode of tube VT2 is connected through a resistance R to thenegative terminal G of the rectifier system. The output of the rectifier is shunted by a filter condenser F01.

The cathode of tube VT]. is connected to the terminal G through a stabilizing resistance SR, the grid and screen grid being returned to points A and B on the resistance R, all of which structure has been described in detail in my copending application hereinbefore referred to.

In this instance, however, I have provided a filter resistance ERA, in the grid circuit of tube VT]. which may be shorted out by a switch 53 depending upon whether it is desired to have or remove any signal current regeneration within the system.

In the arrangement of Fig.1, I connect the plate of tube'VT1 and the grid of tube VTz to the terminal P of the rectifier system through a coupling resistance CR and two series resistances R1 and R2. The condenser C2 serves both as a filter condenser and as signal current condenser for the output circuit of tube VT2. The condenser C3 serves as a filter condenser in conjunction with the resistance R1 completing the signal input circuit for the tube VT2, and it also completes the signal output circuit of tube VTi.

When the switches S1 and S2 are open as shown signal current flowing in the plate circuit of tube VTl developes signal current potentials across both the resistances CR and R2, the total potential being impressed upon the input circuit of tube VT2. If now the switch S1 is closed the plate circuit of tube VT1 is closed through the condenser C5. The impedance input circuit oftube V'Iz remains the same, however, the resultant action being similar to a step-down auto-transformer.

'If, however, the switch S2 is closed the plate circuit of the tube VTl and the grid-circuit of tube VTz are simultaneously completed through the condenser C4, the signal currents in the plate circuitof tube VT]. developing potentials only-across the resistance CR and these same potentials be- "ing applied to the input circuit of tube VTz.

denser C1.

The functions of these condensers are more fully explained with reference to Fig. 2 in which the resistances CR, R2 and R1 of Fig. 1 are designated a, b, 0. With the switches S1 and S2 open the signal current path from the plate to the cathode of tube VT1 is through resistances, a, b, c, and condensers, C2, RC, and BC. The impedance to signal current in the input circuit of tube VT2 is the resistance of a, b, c and the condenser C2.

If the arm of switch S1 is moved across contacts 1, 2, and 3 the impedance of the coupling between tubes may be changed. When on contact 1 the impedance of the condenser C is substituted for the impedance of the series condensers RC and BC in the plate circuit of tube VT1. When the arm of switch S1 is moved to contact 2 the impedance of the section 0 is removed, thus reducing the coupling between tubes to that of the sections a and b. When the arm of switch S1 is moved to contact 3 the section a is the only coupling between tubes VT1 and VTz. The condenser C acts simultaneously to reduce the impedance in both the output circuit of thetube VT1 and the input circuit of tube VT2 because the combination of condensers BCand RC maintains the cathode of tubes VT1 and VT2 at substantially the same signal current potential. However, if either condenser BC or RC has substantial impedance to signal currents a condenser C1 and switch S2 must be provided if it is desired to equalize the signal current impedance in the two circuits.

Referring to Fig. 3, I have modified the circuit arrangement of Fig. 1 to include a tube VT1.

Herein I have shown the cathode of tube VT'1 connected to the terminal G of the source SF through a bias resistance Br, the grid of this tube being returned to the point A on the resistance R which is shunted to the cathode through a con- The plate of tube VT1 and the grid of tube VT1 are returned to a point A on the resistance R. For the tube VT1 I have also provided a hum bucking condenser HBO connected between the cathode and the variable tap D on the resistance R.

In Fig. 4 I have modified the circuit arrangement of Fig. 3 to utilize a screen-grid tube VT1. Herein I have returned the grid of tube VT1 to a point A on a resistance R7, the resistance R1 being of a very high value and functioning in conjunction with the condenser C1 as a filter resistance similar to the function of the resistance FRl of Fig. 1. The screen grid of tube VT1, I have returned to the point E on the resistance R through a filter resistance FR3 which is shunted to the cathode by means of a filter condenser F03. The plate of tube VT1 and the grid of tube VT, I have connected to the terminal P of the source SF through a radio frequency choke coil RCh, a coupling resistance CR1 and resistances R3, R2 and R1, the junction between the resistances CR1 and R3 being shunted to ground by the condenser C5.

In the input circuit of tube VT2 I have made the following change. The plate of tube VT1 and the grid of tube VT2 I have connected to the terminal P of the source SF through the resistances R2 and R1, and have also connected the plate of tube VT1 and the grid of tube VT2 to the center-tap of the filament of the tube VTz through a resistance CR. In other respects the connections are the same as in the circuit arrangement of Fig. 3.

In operating with this change of connection in the grid circuit of tube VTz I obtain a remarkable phenomenon which has the. effect of 'substantially doubling the effective output ability (wattage) of the system over that normally understood to be possessed thereby. For example, in using a Well-known commercial power amplifier tube at VTz rated to give about 1 watts of undistorted output with specified rated energizing potentials, I find that with the same rated potentials and the special connections of Fig. 4, I obtain undistorted output energy at the rate of substantially 3 watts.

In Fig. 5 I have shown the feature of filtration of the screen grid circuit as applied to the tube VT1 of the circuit arrangement of Fig. 1. Herein I have shown the screen grid of tube VT1 energized through the filter resistance FR3 from the potential developed across the resistance R. The value of the resistance FR: is dependent upon the point along the resistance R from which the potential is taken for the screen grid. The screen grid is shunted either to ground or to the cathode of the tube VT1 by means of a condenser C, the only change noticeable in the operation required being a shifting of the point D on the resistance R to which the hum bucking condenser HBO is returned.

In Fig. 6 I have shown a modification of the circuit arrangement of Fig. 5 wherein I have employed a grid filter comprising filter resistance FRl and filter condenser F04, a screen-grid filter comprising filter resistance F133 and condenser FCa; I have further utilized the choking action of the speaker field winding SW in conjunction with the condenser RC to filter hum from the resistance R. I have found that the connection of the condenser C4 from the junction between the resistances CR and R1 and the cathode of tube VT1 serves to adequately reduce the hum of the system to a value below audibility without the use of the hum bucking condenser HBC described with reference to the foregoing figures.

In Fig. 7 I have shown a peculiar utilization of a feature of the circuit arrangement of Fig. 5. If the by-pass condenser I-IBC of Fig. 5 is omitted there will develop a signal current potential across the stabilizing resistance SR so that the grid of tube VTa may be directly connected to the cathode of the tube VT1, the plate thereof being connected to the terminal P of the source SF, the resistance SR serving as the coupling resistance between tubes VT1 and VT2.

In Fig. 8 I have shown the feature of the combination of resistances CR, R2, R1 and the condenser C3 incorporated in a two tube direct coupled system. The effect of this combination in the output wattage of a two tube system as shown in this figure is even more noticeable than when utilized in the three tube system, the operation of which was described with reference to Fig. 4.

In Fig. 9 I have shown the circuit arrangement of Fig. 4 modified in such a manner that tube VT1 functions primarily as a radio frequency amplifier, the input for the system comprising a tunable transfer circuit T1 energized from an Antenna Ant, through a volume control system comprising an antenna resistance and a condenser Cs. In this arrangement I have replaced the radio frequency choke coil RCh of Fig. 4

-with a tunable circuit T2 comprising an inductance L2 and a variable condenser VCz connected in the manner shown, and have connected the condenser C5 between the junction between the inductance L2 and ground. In this arrangement the bias for the tube VT1 is determined by .the

proportioning of the resistances SR, CR, R3, R2,

, and R1 as in the arrangement of Fig. l. The

signal input for tube VTr however isdetermined by the impedance of the tuned circuit T2 to cur rents of signal frequency, the input circuit to the cathode of tube V T1 being closed through a condenser C6. The variable connection between the plate of tube VTi and the inductance L2 functions in the same manner as the variable tap on an auto-transformer to vary the coupling between the tubes VT1 and VT1. Between the plate of tube VTz and the cathode I have connected a radio frequency by pass condenser RFC to shunt radio frequency currents away from the output transformer OT. This condenser, while helpful, is not essential to the operation of the circuit arrangement illustrated in this figure.

In Fig. 10, I have shown a direct coupled tube system functioning as a radio frequency amplifier system and a direct coupled tube system functioning as a detector amplifier system connected in cascade and energized from a common source of fluctuating unidirectional current SF. Across the terminals P and G of the source SF I have connected the primary of the output transformer OT, the anode to cathode path of tube VTz and the resistance R. In shunt to the anode to cathode path of tube VTz I have connected two high resistances R1 and R2, and have energized the grid of tube VTz and the plate of tube VTl by connecting the same through the coupling resistance CE. The tube VT1 is otherwise energized in the manner described with reference to the foregoing figures, the tunable 1 input circuit T1 thereof being provided with a filter s" stem including filter resistance F334 and filter condenser FC4 as previously described with reference to Fig. 6 hereof. I

Across the terminals G and P of the source SF I have connected a potentiometer R from which I have energized a four stage direct coupled tube system VT1, VT2, VT1, VT2 by connecting the cathode of tube VTi to the terminal G of the source SF through a stabilizing resistance SR1 which is shunted by a signal current condenser Ci, andconnecting the cathodes of tubes VT'z, VT1, VT2 and directly to the points G2, G3 and G4 of the potentiometer R, each of these points being by-passed to ground by condensers B01, BCz B03 respectively, and the remaining electrodes as follows: The grid of tube VT'i is connected through a tunable input circuit, such as a loop LP, to the point A1 on the resistance B, the resultant voltages between the cathode of tube VT'1 and the point A1 on the resistance R. stabilizes the four tube direct coupled system in the same manner as the voltages between the cathode of tube VTl and the point A on the resistance R stabilize the two tube direct coupled system as has been described in detail with reference to Fig. 5 in my copending application hereinbefore referred to. The screen grids of tubes VT'1, VTz, VT1 and VT2 are respec-' tively connected to points B1, B2, B3 and B4 on the potentiometer R of proper voltage with respect to the points G, G2, G3 and G4. The plate of tube VTi and the grid of tube VT'z are returned to the point A2 on the potentiometer B through th coupling resistance CR1. The plate of tube VT2 and the grid of tube VT"1 are returned to the point As on the potentiometer B through a coupling circuit including inductance L2, condenser V02, resistance CR2 and condenser Co as hereinbefore described with reference to "'1; Fig. 9. The plate of tube VT1 and the grid of tube V'I"2 are connected to the point Al on the potentiometer R. The plate of tube VT2 is connected to the terminal P of the source SF through a plate resistance PR, and coupled to the grid of tube VT1 through a coupling condenser CC.

The operation of this circuit arrangement is as follows: The input circuit LP selectively impresses signal currents voltages upon the grid of tube VTi.

The tube VT'1 amplifies these signals and aperiodically impresses them on the grid circuit of tube VTz by means of the coupling resistance CR1. The tube VT'z further amplifies the signals and selectively impresses them on the grid circuit of tube VT1 through the tuned circuit T2. The tube VT1 further amplifies these signals and aperiodically impresses them on the grid circuit of tube VT"2 by means of the coupling resistance CR3. The tube VT"2 further amplifies the signals and develops signal current potentials across the resistance PR. which po tentials are resonantly abstracted from this resistance by the tuned circuit T1 coupled thereto through the condenser CC. The tubes VT1 and VT2 then detect and amplify the amplified high frequency currents in the manner fully set forth in copending application of Sidney Y. White, Serial No. 318,754, filed July 29, 1929.

While I have illustrated and described my invention as embodied in certain specific circuit arrangements it is to be understood that various modifications thereof may be made without departing from the spirit of my invention as defined by the claims appended hereto.

Having thus described my invention, what I claim is:

1. In an electron tube system, the combination of a plurality of electron tubes direct coupled in cascade through a common impedance element and means for varying the effective value of said impedance with respect to signal currents while maintaining the value of said impedance constant with respect to direct currents flowing therethrough, said means consisting of a condenser variably connected between selected points on said impedance and the cathode of one of said tubes.

2. In an electron tube system, the combination of a plurality of electron tubes direct coupled in 1.

cascade through a common impedance element and means for varying the effective value of said impedance with respect to signal currents while maintaining the value of said impedance constant with respect to direct currents flowing therethrough, said means consisting of a condenser variably connected between selected points on said impedance and the cathode of the tube containing said impedance within its plate circuit.

3. In an electron tube system, the combination 1,

of a plruality of electron tubes direct coupled in cascade through a common impedance element and means for varying the effective value of said impedance with respect to signal currents while maintaining the value of said impedance constant with respect to direct currents flowing therethrough, said means consisting of a condenser variably connected between selected points on said impedance and the cathode of the tube containing said impedance within its grid circuit.

4:. In an electron tube system, the combination of a plurality of electron tubes direct coupled in cascade through a common impedance element and means for varying the eifective Value of said impedance with respect to signal currents while maintaining the value of said impedance constant with respect-to direct currents flowing therethrough, said means consisting of condensers variably connected between selected points on said impedance and the cathodes of each of the tubes containing said impedance within their circuits.

5. In an electron tube system, the combination of a plurality of tubes direct coupled in cascade, a source of current for energizing the electrodes of said tubes, a common. impedance element through which the plate-circuit of one tube and the grid circuit of another tube are energized and a high resistance element connectedflbetween the grid and cathode of said other tube.

6. In an electron tube system, the combination of a plurality of electron tubes direct coupled in cascade, the coupling element between two tubes comprising a plurality of energy transfer elements one of which hashigh impedance to high frequency currents and low impedance to low frequency currents and another of whichhas high but substantially like impedance for currents of both frequencies.

'7. In an electron tube system, the combination of a plurality of electron tubes direct coupled in cascade, the coupling element between two tubes comprising a tunable circuit and a high impedance of substantially constant value to low frequency currents.

8. In an electron tube system, the combination of a plurality of electron tubes direct coupled in cascade, the coupling element between two tubes comprising a tunable circuit and a high inipedance of substantially constant value to low frequency currents and means for shunting high frequency currents around said last mentioned impedance.

9. In an electron tube signal transfer system including a source of fluctuating unidirectional potential, means and connections for energizing tube electrodes of said system, and an electron discharge tube having'the average potential difference between its cathode and control electrode differentially determined by two potential developing elements one of which is disposed for energization by discharge current of said same tube and the other of which is disposed for energization predominantly at least by discharge current of another tube of said system, the combination therewith of a condensive-resistive impedance having its resistive element arranged between said cathode and control electrode for lowering the potential of said controlelectrode under the influence of space charge current therethrough and having both its elements so arranged as to divert from said two potential developing means fluctuating components of said source.

10. In an electron tube signal transfer system including a source of fluctuating unidirectional potential, means and connections for energizing tube electrodes of said system, and a screen-grid electron discharge tube having the average potential difference between its cathode and control electrode differentially determined by two potential developing elements one of which is disposed for energization by discharge current of said same tube and the other of which is disposed for energization predominantly at least by discharge current of another tube of said system, the combination therewith of a resistive element in the screen-grid connection of said screen-grid tube, and a condenser disposed between said resistive element and a potential point in said two potential developing elements, whereby fluctuat- 195 ing components of said source are diverted from said screen grid and the potential of said screen grid is lowered under the influence of space current therethrough.

11. In an electric signal transfer system including two electron discharge tubes, a source of potential, and means for energizing tube electrodes of said system from said source, the combination of a potential developing means common to the cathode-anode and cathode-control electrode circuit of the one of said two tubes, and a connection between a point in said potential developing means and the control electrode of the other of said two tubes, whereby through said connection signal energy is transferred from said one tube to said other tube.

GERARD J. KELLEY.

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