US1755938A - Amplification system - Google Patents

Amplification system Download PDF

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Publication number
US1755938A
US1755938A US274174A US27417428A US1755938A US 1755938 A US1755938 A US 1755938A US 274174 A US274174 A US 274174A US 27417428 A US27417428 A US 27417428A US 1755938 A US1755938 A US 1755938A
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US
United States
Prior art keywords
grid
tube
cathode
current
circuit
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US274174A
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English (en)
Inventor
Thompson Lincoln
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
WM H BRISTOL TALKING PICTURE C
WM H BRISTOL TALKING PICTURE Corp
Original Assignee
WM H BRISTOL TALKING PICTURE C
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority to NL29122D priority Critical patent/NL29122C/xx
Application filed by WM H BRISTOL TALKING PICTURE C filed Critical WM H BRISTOL TALKING PICTURE C
Priority to US274174A priority patent/US1755938A/en
Priority to FR673961D priority patent/FR673961A/fr
Priority to GB13590/29A priority patent/GB310857A/en
Application granted granted Critical
Publication of US1755938A publication Critical patent/US1755938A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
    • H03F3/26—Push-pull amplifiers; Phase-splitters therefor
    • H03F3/28—Push-pull amplifiers; Phase-splitters therefor with tubes only

Definitions

  • CONNECTICUT A. CORPORATION OF CONNECTICUT AMPLIFICATION SYTEM Application mea nay 1, 192s. Serin No. 274,174.
  • the invention' relates to an amplifying sys-r tem for weak electric currents and more especially to a system utilizing thermionlc valves or so-called audion tubes for this purpose.
  • This substantially distortionless amplification has been accomplished by impressing on the grid of an amplifying valve a potential permanently more negative than that of its cathode, 'or biasing negatively said grid.
  • the magnitude of this bias or negative potential dependson the grid potential-plate current characteristic of the particular tube employed, it being understood that the amount of grid current will be negligible until the signal voltage attains a value sufficient to make the grid reach or exceed the filament potcntial.
  • appreciable grid current fiows at a slightly negative potential, the current then flowing introducing a shunt load on the signal source and, in the ordinary well-known amplification circuit causing distortion of the input signal wave form which is correspondingly magnified in the amplified circuit. If the valve, however, were operated without providing the aforesaid grid bias, the entire positive, pulsations of the signal would be subject ⁇ to this shunt load and the negative pulsations be subjected to practically no load,
  • Vacuum tube design has, therefore, been along the lines of constructing tubes such that their characteristic curve will show as great a useful portion to the negative side of the zero grid potential line as possible in order to give Imaximum undistorted output.
  • some tubes in use have no useful portion on the positive side. This, however, entails a loss' of amplifying power of the tube, that is to say, in the number of milliamperes change of the plate current for a unit ⁇ v change in the grid voltage and therefore less steep gradient.
  • the present invention has for its object a novel system whereby this increased amplification ratio is secured, it being possible to operate a tube under substantially distortionless amplification and with the tube having no bias whatsoever or otential impressed permanently on its gri or, if any be thus permanently impressed thereon, the same being a positive one.
  • a novel system or method of balancing which includes setting up positive grid currents in phase with the oscillating voltage applied to the input circuit of the tube and thereby rendering their effect on distortion negligible. This entails no sacrifice of amplification ratio, although the grid circuits consume appreciable energy in their operation yet this is more than compensated for by the increased amplifying power. By properly designing the circuits to allow for the grid energy consumption, excellent quality is attained and at tremendous volumes.
  • a further object of the invention contem-l plates a system wherein grid leaks may be dispensed with, provision being made for the 'discharge of any accumulated potential through circuits employed in the operation of vthe novel system.
  • rent ioWing therein is balanced or com ensated so that distortion is substantially o viated and a high amplification ratio attained.
  • Fig. 1 is a diagrammatic view illustrating the novel amplification system as applied in connection with a microphone.
  • Fig. 2- illust'rates one arrangement for combining the outputs of the two thermionic valves of thesystem illustrated in Fig. 1.
  • Fig. 3 is a diagrammatic representation of the novel amplifying system embodying a modification.
  • Fig. 4 is a diagrammatic view of the novel ampllfying system connected with, -for l example, a detector tube or lower amplification stage.
  • Figs. 5 and 6 are similar views illustrating7 different means of coupling.
  • igs. 7 and 8 are diagrammatic views of the amplifying system showing a modification in the compensating arrangement.
  • Fig. 9 illustrates the arrangement for feeding the filaments of the tubes employed in the novel amplifying system from a source of alternating current.
  • an input circuit designating a suitable Vinductance thereof receiving a single voltage in anywell-known or special manner and from which inductance extends a lead 11 connected directly to the grid 12 of an amplifying tube 13, preferably of so-called hardor highly evacuated type and of high ampliplate or anode 14 andthe lament or cathode 15.
  • a further lead 16 directly connects the latter to said inductance; and the lament or cathode 15 and plate or anode 14 are connected in the usual manner to the A and B batteries 17 and 18 respectively in ac plifying circuit except that no C battery is included in circuit for biasing negatively the grid 12, nor is there provided any gridleak in connection therewith.
  • the novel system operates best when preceded by a signal:
  • a source of low impedance for example, a carbon microphone 19 which feeds the in ut circuit, through the inductance 10 mate ed thereto, excellently because ofits ability to deliver current even at fairlyhigh steppedup voltage.
  • both the grid 21 and its cathode 23 are thereby also directly connected to the input circuit.
  • Means, independent of the filament and vplate energizing batters 17 and 18, are also to ybe provided for the cathode 23 and anode '22 of this second tube, for example A and B batteries 26 and 27 respectively.
  • this tube should be of fairlylow impedance and the coupling may be effected in any of the customary ways.
  • an impedance 31 may be bridged across the plate circuit of said tube to carry oHthe direct current, while a condenser 32 is inserted in series in the lead 33 therefrom to allow the alternating voltages impressed on the grid circuit of the tube to Abe conitinued to t-he amplifyin portion com- ,the plate circuit of the tube 3 while in Fig.
  • transformerv couplin a typical transformerv couplin is shown, the primary of transformer 38 bem bridged across the plate circuit of tube 39 an matched .to its. late im edance, while-the secondary thereo is matc ed to the grid impedance of the grid circuit to attain maximum efliciency.
  • the matching is designed for the desired frequency,.say a proximately 800 cycles.
  • this balancing or compensation may be accomplished, also, b disconnecting entirely the p ate circuit o one of the tubes as the tube 40, or utilizing a plateless tube, and including a variable resistance element 41 in the grid lead 42 from the grid of the other tube 43.
  • This resist-ance is to be adjusted to give equal grid-current grid-voltage curve with the main amplifier tube- 43, as the usual two-.element tube does not possess generally the 4desired characteristic for'matching the grid-current grid-voltage ofsaid tube 43.
  • a two-element tube or its equivalent such as a crystal or other uni-lateral device (not shown) whose voltage-current curve can beadj usted to equal more or less exactly thevoltage-current curve of the amplifier tube may be utilized for this purpose.
  • Means may be devised to reduce the grid current, for example, by placing in series the grid circuits of two or more tubes 46 and 47 combined with a tube 48, Fig. 8, and compensating as hereinbefore noted, as with the va'- riable resistance element 49 and plateless tube 48.
  • the filaments or cathodes are vadapted for energization from a source of thiiough a suitable transformer 53 and the returii lead 54 of the one grid 5 5 is not required to be made to return to the electrical center of the other tube for minimized hum, thus eliminating the necessity for center taps in 'the :transformer winding.
  • An oscillating voltage applied to the input circuit will, therefore, set up oscillating currents in the interconnected grid filament circuit of the two tubes and in phase with the applied oscillating voltage.
  • the said interconnected circuit will then act as an ordinary ohmic resistance across the input circuit 11-16, alternating positive and negative portions'of the applied signal equally since the tubes 13 and 2() are designed to match.
  • the preceding ⁇ stages in a system of the nature herein set forth may be operated at positive or zero potential; and it has been .found generally advantageous to operate one ⁇ or more leading stages at a predetermined positive bias.
  • the variable grid imped-,- ance is the factor which usually produces distortion in vamplitying systems, there is sel lected in the present embodiment a point in the grid-voltage grid-current curve at which thisgrid impedance, although low, is conl stant.
  • the said curve is substantially a iis isc
  • the biasing point selected is to be located substantially midway between the zero voltage position and the point where said curve begins to depart from its straight line characteristic. This will permita tube to handle without distortion fairly large variations in voltage abut when the compensated arrangement is to be provided as in larger amplilications, as the final or power stages of a system, the grid is to be operated at substantially the zero voltage position-fthe combined grid impedancespf the two tubes employed being equal only to that of one tube.
  • a unilateral device included in the said input circuit having its voltage-current characteristic adjusted to match the grid-voltage gridcurrent characteristic of said thermionic valve and thereby to direct current through said unilateral device such that equal positive and negative voltages applied to the input circuit cause substantially equal iiows of current respectively between said cathode and the said controlling element and through the said unilateral device.
  • a unilateral device included inparallel with said input circuit, having its 'voltage current characteristic adjusted to match the that equal positive and negative voltages aplied to the input circuit cause substantialy equal flows of current respectively between said cathode. and the said controlling element and through theV said unilateral device.
  • anode and cathode included in a suitably energized circuit and an input circuit connected to the said controlling element and cathode: means for impressing upon the controlling element of said valve a potential more positive than that of its cathode; and a unilateral device included in the said input circuit, having its voltage-current characteristic adjustedto match the grid-voltage gridcurrent characteristic of said thermionic valve and thereby to direct current through said unilateral device such that equal positive and negative voltages applied to the input circuit cause substantially equal flows of current respectively between said cathode and the said controlling element and through the said unilateral device.
  • an amplifying system having a thermionic valve with controllingelement, and anode and cathode included in a suitably en'- ergized circuit, and an input circuit connected to the said controlling element and cathode a second thermionic valve with controlling element, and anode and cathode included in a suitably energized circuit, the controlling element thereof' being connected to the said input circuit and to the first-named cathode and the cathode thereof to the first-named controlling element to direct current between the last-named cathode and last-named controlling element such that equal positive and negative voltages applied to the input circuit will cause substantially equalflows of currentv respectively between the rst-named cathode and its controlling element and the being connected to the cathode of the other and the said controlling elements and cathodes to the input circuit.
  • anode and cathode included in a suitably energizedcircuit, and an input circuit means for impressing upon the Controlling element of said valve a. potential more positive than that of its cathode; and a second thermionic valve with controlling element, and anode and cathode included in a suitably energized circuit, the grid-current grid-voltage characteristic of the second valve being matched to the grid-current grid-voltage characteristi'c of the first-named valve and the controlling element of each valve being connected to the cathode of the other and the said controlling elements and cathodes to the input circuit.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Amplifiers (AREA)
US274174A 1928-05-01 1928-05-01 Amplification system Expired - Lifetime US1755938A (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
NL29122D NL29122C (enrdf_load_stackoverflow) 1928-05-01
US274174A US1755938A (en) 1928-05-01 1928-05-01 Amplification system
FR673961D FR673961A (fr) 1928-05-01 1929-04-24 Perfectionnements aux systèmes amplificateurs pour courants électriques faibles
GB13590/29A GB310857A (en) 1928-05-01 1929-05-01 Improvements in or relating to amplifying systems for weak electric currents

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US274174A US1755938A (en) 1928-05-01 1928-05-01 Amplification system

Publications (1)

Publication Number Publication Date
US1755938A true US1755938A (en) 1930-04-22

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ID=23047100

Family Applications (1)

Application Number Title Priority Date Filing Date
US274174A Expired - Lifetime US1755938A (en) 1928-05-01 1928-05-01 Amplification system

Country Status (4)

Country Link
US (1) US1755938A (enrdf_load_stackoverflow)
FR (1) FR673961A (enrdf_load_stackoverflow)
GB (1) GB310857A (enrdf_load_stackoverflow)
NL (1) NL29122C (enrdf_load_stackoverflow)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2496317A (en) * 1946-12-24 1950-02-07 Harry B Smith Combining circuit

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL185175B (nl) * 1954-02-16 Kendall & Co Werkwijze voor het isoleren van een buisvormig voorwerp.

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2496317A (en) * 1946-12-24 1950-02-07 Harry B Smith Combining circuit

Also Published As

Publication number Publication date
FR673961A (fr) 1930-01-22
NL29122C (enrdf_load_stackoverflow)
GB310857A (en) 1930-08-01

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