US2213871A - Thermionic amplifier - Google Patents

Thermionic amplifier Download PDF

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Publication number
US2213871A
US2213871A US186062A US18606238A US2213871A US 2213871 A US2213871 A US 2213871A US 186062 A US186062 A US 186062A US 18606238 A US18606238 A US 18606238A US 2213871 A US2213871 A US 2213871A
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US
United States
Prior art keywords
circuit
feed
input
grid
amplifier
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
US186062A
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English (en)
Inventor
Strong Charles Eric
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.)
International Standard Electric Corp
Original Assignee
International Standard Electric Corp
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 claimed from GB6814/37A external-priority patent/GB491803A/en
Application filed by International Standard Electric Corp filed Critical International Standard Electric Corp
Application granted granted Critical
Publication of US2213871A publication Critical patent/US2213871A/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
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F1/00—Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements
    • H03F1/34—Negative-feedback-circuit arrangements with or without positive feedback
    • H03F1/36—Negative-feedback-circuit arrangements with or without positive feedback in discharge-tube amplifiers
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
    • H03F3/20—Power amplifiers, e.g. Class B amplifiers, Class C amplifiers
    • H03F3/22—Power amplifiers, e.g. Class B amplifiers, Class C amplifiers with tubes only
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
    • H03F3/50—Amplifiers in which input is applied to, or output is derived from, an impedance common to input and output circuits of the amplifying element, e.g. cathode follower
    • H03F3/52—Amplifiers in which input is applied to, or output is derived from, an impedance common to input and output circuits of the amplifying element, e.g. cathode follower with tubes only

Definitions

  • This invention relates to an improved method of stabilising high frequency amplifiers by the application of controlled feed-back in a particular manner.
  • a known method of overcoming this effect consists in neutralising the unwanted coupling by applying additional coupling having an equal and opposite effect.
  • a pushpull amplifien'for example it is known to add balancing condensers between the plate of each valve and the grid of the other, these condensers forming, together with the valve plate to grid capacities, a balanced bridge about which the .20 input and output circuits are conjugate to each other.
  • the aim is to secure stabilisation by the elimination within practical limits of all feed-back.
  • An alternative method of obtaining stability consists not in the elimination of all feed-back but in arranging that feed-back should exist and should be in the reverse sense and so applied that the known criterion ior'stability (as enunciated for example by H. Nyquist in the Bell System Technical Journal, January 1932, page 126) should be met. Any coupling inherent in the system tending to cause instability is swamped by the applied reverse feed-back.
  • This invention relates to a novel application of this method.
  • the object of the invention is to avoid certain practical difficulties which are experienced in the adjustment and operation of balanced am plifiers of the general form described above, such difiiculties, for example, as change of balance 40 with frequency due to unbalanced inductance in the bridge circuit, difficulties in the construction and mounting of suitable balancing condensers in the case of a high voltage, high power amplifier, and instability arising from the presence of resonant circuits made up of balancing condensers and unavoidable inductance in the leads thereto.
  • the method disclosed in this invention consists in arranging that the input or driving circuit is in series with the plate to cathode output is applied to cancel some of the negative feedback if the latter is unnecessarily great.
  • FIG. l is a diagrammatic illustration of a circuit in accordance with the invention.
  • Figs. 2 and 3 are equivalent diagrams used for explaining the operation of the circuit of my invention.
  • Fig. 4 illustrates a modification'of the grid connections in accordance with another feature of my invention.
  • valves are arranged with their grids connected together and to ground and the driving voltage is applied between the filaments.
  • the driving circuit For the purpose of obtaining reverse feed-back by reason of the fact that the driving circuit is in series with the plate to filament output circuit the driving circuit has appreciable impedance to currents of the working frequency, the amount of reverse feed-back depending on the value of that impedance.
  • I and 2 pull, 3 and 4 are tuned input and output circuits inductively coupled by the coil 5 which'is in series with the input circuit.
  • the filaments are heated by direct or alternating current fed through double wound choke coils 6 and 1. These coils havea'high impedance at frequencies at which the amplifier operates.
  • the amplifier will be stable.
  • the circuit lies in the fact that notwithstanding the presence of two tuned circuits, the phase of the reverse feed-back applied in the manner indicated is not shifted through 180 for any frequency and, therefore, when no added positive feed-back is applied, the circuit does not meet the conditions for instability at anyfrequency even when the gain reduction due to feed-back is high.
  • the negative feed-back being of such a relatively invariable nature'can effectively overcome and swamp other sources of feed-back which may exist in the circuit and which may change in phase relatively more rapidly with frequency.
  • the reverse feed-back volt- For the values taken the current delivered by the generator is 1.0 ampere and the reverse feedback voltage is 2,000.
  • a thermionic amplifier which is stable over a large frequency range comprising a valve having grid, cathode and plate; electrodes, means connecting said grid electrode to ground, an input circuit for applying input voltage to said cathode electrode said input circuit having a substantial impedance to waves in, said frequency range, an output circuit coupled to said plate electrode, 7 and completed through said cathode electrode, whereby a feedback in a reverse sense with respect to said input voltage is set up by said output current, and positive feedback means coupling said input and output circuits for regulating the amount of resultant reparticular frequency range, comprising a pair of valves arranged in push-pull, each of said valves having grid, cathode and plate electrodes, means connecting said grid electrodes to ground, an
  • An amplifier according to claim 3 further comprising variable capacity means in said means connecting said grids to ground, for substantially reducing inherent inductive coupling between said input and output circuits due to the inductance in said leads.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Amplifiers (AREA)
US186062A 1937-01-22 1938-01-21 Thermionic amplifier Expired - Lifetime US2213871A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB238067X 1937-01-22
GB6814/37A GB491803A (en) 1937-01-22 1937-03-08 Improvements in or relating to thermionic amplifiers

Publications (1)

Publication Number Publication Date
US2213871A true US2213871A (en) 1940-09-03

Family

ID=32071222

Family Applications (2)

Application Number Title Priority Date Filing Date
US186062A Expired - Lifetime US2213871A (en) 1937-01-22 1938-01-21 Thermionic amplifier
US192083A Expired - Lifetime US2241892A (en) 1937-01-22 1938-02-23 Thermionic amplifier

Family Applications After (1)

Application Number Title Priority Date Filing Date
US192083A Expired - Lifetime US2241892A (en) 1937-01-22 1938-02-23 Thermionic amplifier

Country Status (5)

Country Link
US (2) US2213871A (fr)
BE (1) BE425863A (fr)
CH (1) CH238067A (fr)
FR (1) FR832354A (fr)
GB (1) GB489289A (fr)

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2750450A (en) * 1951-04-20 1956-06-12 Rca Corp Series connected totem-triode amplifiers
US2692919A (en) * 1951-06-11 1954-10-26 Rca Corp Stabilized driven grounded grid amplifier circuits
US2756283A (en) * 1951-11-13 1956-07-24 Rca Corp Cathode input amplifiers
US2795694A (en) * 1954-09-27 1957-06-11 Standard Coil Prod Co Inc Cascode amplifier with signal and a. g. c. voltages applied to different stages

Also Published As

Publication number Publication date
FR832354A (fr) 1938-09-26
US2241892A (en) 1941-05-13
CH238067A (de) 1945-06-15
BE425863A (fr)
GB489289A (en) 1938-07-22

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