US1386731A - Vacuum-tube repeater-circuits - Google Patents

Description

H. S. READ.

VACUUM TUBE REPEATER CIRCUITS.

APPLICATION FILED APR. 12, 1919.

1,386,731., Patented Aug. 9, 19211..

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HARRY S. READ, OF EAST ORANGE, NEW JERSEY; ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, 013 NEW YORK, N". 1., A CORPORATION OF NEW YORK,

Specification of Letters Patent.

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Application filed April 12, 1919. Serial No. 289,608.

To all whom it may concern:

Be it known that I, HARRY citizen of the United States, residing at East Orange, in the county of Essex, State of New Jersey, have invented certain new and useful Improvements in Vacuum-Tube Repeater-Circuits, of which the following is a full, clear, concise, and exact description.

This invention relates to vacuum tube r'epeaters and a method of operating the same, and more particularly to arrangements of such repeaters wherein the cathodes of a plurality of vacuum tubes are so connected that heating current from a common source passes therethrough in series.

Vacuum tubes, when used in repeater circuits, are frequently found to operate more satisfactorily when the control electrode is normally maintained at a negative potential with respect to the cathode. In circuits of the type above referredto, it has been proposed to obtain the necessary steady potential difference between the control electrode and the cathode of a vacuum tube, by connecting the control electrode of one of the vacuum tubes to a point in the heating circuit such that the potential of the control electrode is ne ative with respect to its corresponding cathode by the drop in potential across the cathode of another tube. Such an arrangement is disclosed andclaimed in the patent application of E. O. Scriven, Serial No. 242,183, filed June 27, 1918.

In certain circuits of this type it has been found that the negative potential of the control electrode, if derived from the total drop across another tube, is rendered too great for the proper operation of the corresponding tube.

It is an object of this invention to provide a simple, easily controlled means for applying only a portion of the potential drop across a cathode to the control electrode of another tube.

This is accomplished in the preferred form of the invention by connecting a resistance across the terminals of a cathode and tapping ofl from a point on this resist ance through a connection to the control electrode of another tube.

In circuits employing a plurality of vacuum tubes of different types, some of the tubes may require more cathode heating current than others. To prevent overheating S. READ, a

of such cathodes when all the cathodes are connected in series to a source of heating current, this invention provide a method and means for by-passing a portion of the current about each of the cathodes likely to be overheated. This insures sutlicient hurrent in the other cathodes when the potential of the source is limited. :In certain instances this by-path serves the threefold purpose of (1) preventing overheating in the cathode that can use less current, (2) causing suificient current in the filament that can use more current, and (3) providing a means for supplying to the control electrode of another tube a potential corresponding to that of a point intermediate the ends of the cathode which is shunted by the resistance.

The invention will be more fully understood from the following detailed description and claims taken in connection with the accompanying drawing which shows diagrammatically a detector-amplifier circuit embodying the invention.

Referring to the drawing by reference numerals, the vacuum tube 10 is employed in a detector unit having its input circuit connected at the terminals 11 and 12 in any desired or usual manner to a receiving antenna or other circuit adapted to have signal impulses produced therein. The input circuit contains a series condenser 13 and a shunt condenser 14: and is grounded at 15.

The output circuit of tube 10 is connected to the first tube of a three-stage amplifier comprising the vacuum tubes 16, 17 and 18, all four of the tubes 10, 16, 1? and 18 being arranged in tandem. The filamentary cathodes 19, 20, 21 and 22 of tubes 10, 16, 17 and 18 .are in series with each other and with a source of heating current shown in the drawings as a battery 10, having its negative pole directed toward the adjustable resistance 23.

While in .the drawings all of the tubes are shown schematically as being alike, in the actual circuit which is represented herein,

tubes 10 and 18 were of a type operating more satisfactorily with a. lower filament temperature than tubes 16 and 17, and to prevent the overheating of cathodes 19 and 22, shunt resistances 24 and 25 were provided to carry a portion of the current. Values of 25 ohms and 20 ohms, respectively,

Patented Aug. 2, 1921.

were found to be suitable for these resistances.

Space current is supplied to allof the tubes from a source shown in the drawings as'a battery 41, the negative pole of which is connected to the cathode heating circuit and the positive pole is connected to the plate electrodes or anodes 26 in multiple through the resistances 27. An inductance 28 is also placed in the path to the anode of the detector tube 10, and a condenser 29 is bridged across the output circuit of this tube. The anode of each tube is connected to the grid or control electrode 30 of the succeeding tube through a condenser 31.

The tube 16 is found to operate more satisfactorily, if its grid 80 is normally maintained negative with respect to cathode 20 by a potential difference less than the drop in potential of the heating current through the preceding cathode 19. This negative potential is pbtained by connecting the grid through resistance 32 to a suitable tap on the resistance 24. In the circuit set up as above referred to, the portion 24 of this resistance, was 20 ohms and the portion 24 was 5 ohms. A similar connection is made to the grid of tube 17 from a resistance 35 bridged across the cathode 20. This resistance had a value of 125 ohms so as to bypass only a negligible amount of heating current, and satisfactory operation was obtained when the grid connection divided it into two parts 35 of 100 ohms and 85 of 25 ohms.

A means for controlling the ratio of amplification of the set is provided in the resistance 36 which is arranged .as a potentiometer with to the grid of tube 17. A

The negative grid potential for the tube 18 in this circuit is required to be greater than for the preceding tubes, and is obtained by a connection through the resistance 37 to a point adjacent the negative end of the filament 21', thereby obtaining the total drop in potential across this filament.

The output from the tube 18 passes through a suitable receiving device 38, shown as a telephone receiver, and a path for alternating currents is provided by the condenser 39. r

While a more uniform amplification throughout a wide range of signal frequencies can be obtained by using non-inductive resistances 27 32, 36 and 37, satisfactory operation canalso be had if these resistances are inductive. For example, in the output circuit of the detector tube 10, the inductance 28- is inserted in series with the resistance 27 in order to provide the desired impedance to alternating currents.

While the invention has been shown embodied in a specific circuit, it is to be under-- stood that it is of general application in cira series of taps for connectioncuits employing a plurality of vacuum tubes and is to be limited only by the scope of the following claims.

What is claimed is: 1. In a multi-stage repeater, a plurality of electrode of another of said tubes substantially at the same potential as that of a point intermediate the ends of said first mentioned cathode.

3. In combination, a plurality of vacuum tubes arranged in'tandem, said tubes having filamentary cathodes so connected that heating current -flows serially through said cathodes, a resistance bridged across one of said cathodes, and a connection from a point on said resistance to the control electrode of another of said tubes.

4:. In amulti-stage repeater, a'p'lurality of vacuum tubes each having a cathode, an anode and a' control electrode, said cathodes being. so connected that heating current flows serially therethrough, a resistance bridged across one of said cathodes, and a connection from a point on said resistance to the control electrode corresponding to a cathode which is more positive than said first-mentioned cathode.

5. In a multi-stage repeater, a plurality of vacuum tubes each having a cathode, an anode and a control electrode, and means comprising a resistance bridged across the cathode of one of said tubes for maintaining the control electrode of another of said tubes at substantially the same otential as that of a point intermediate t e ends of said cathode.

6. A vacuum tube translating device comprising a cathode, an anode and a control electrode, a source of heating current in circuit with said cathode, a low resistance'serially connected between said cathode and said source, a high resistance in shunt to a portion of said heating current circuit including said low resistance, and a connectionvacuum tubes 'each having a cathode, an

cuit with said cathode, a low resistance serially connected between said cathode and the negative terminal of said source, a high resistance, a connection from said hi h resistance to a portion of said heating circuit,

a second connection from said high resistance to another portion of said heating circuit, said high resistance being in shunt to a portion of said heating current circuit including said low resistance, and a third connection from said high resistance and leading to said control electrode.

8. In combination, a plurality. of vacuum tubes each having a cathode an anode and a control electrode, said cathodes being so connected that heating current passes serially therethrough, one of said tubes being of a type which requires less heating current 20 than another of said tubes, a resistance bridged about the cathode of said first mentioned tube, and a connection from a oint on said resistance to the control electrode of another of said tubes.

9. In combination, a plurality of vacuum tubes each having a cathode, an anode and a control electrode, said cathodes bein so connected that heating current flows serlally therethrough, a resistance in shunt to a portion of the heating current circuit contain ing one of said cathodes, and means comprising a connection from an intermediate point on said resistance to the control electrode of another of said tubes for determining the potential difi'erence between said last mentioned control electrode and its cathode.

In witness whereof I hereunto subscribe my name this 10th day of April, A. D, 1919.

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