US2252049A - Linear amplifying system - Google Patents

Linear amplifying system Download PDF

Info

Publication number
US2252049A
US2252049A US273404A US27340439A US2252049A US 2252049 A US2252049 A US 2252049A US 273404 A US273404 A US 273404A US 27340439 A US27340439 A US 27340439A US 2252049 A US2252049 A US 2252049A
Authority
US
United States
Prior art keywords
wave
amplifier
output
input
linear
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
US273404A
Other languages
English (en)
Inventor
Frederick E Terman
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 to BE474454D priority Critical patent/BE474454A/xx
Application filed by International Standard Electric Corp filed Critical International Standard Electric Corp
Priority to US273404A priority patent/US2252049A/en
Priority to GB3871/40A priority patent/GB537558A/en
Priority to FR865592D priority patent/FR865592A/fr
Application granted granted Critical
Publication of US2252049A publication Critical patent/US2252049A/en
Priority to ES176812A priority patent/ES176812A1/es
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • 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
    • H03F1/02—Modifications of amplifiers to raise the efficiency, e.g. gliding Class A stages, use of an auxiliary oscillation
    • H03F1/04—Modifications of amplifiers to raise the efficiency, e.g. gliding Class A stages, use of an auxiliary oscillation in discharge-tube amplifiers
    • H03F1/06—Modifications of amplifiers to raise the efficiency, e.g. gliding Class A stages, use of an auxiliary oscillation in discharge-tube amplifiers to raise the efficiency of amplifying modulated radio frequency waves; to raise the efficiency of amplifiers acting also as modulators
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03C—MODULATION
    • H03C1/00—Amplitude modulation
    • H03C1/02—Details
    • H03C1/06—Modifications of modulator to reduce distortion, e.g. by feedback, and clearly applicable to more than one type of modulator
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
    • H03F3/02—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements with tubes only

Definitions

  • the ⁇ present invention relates to amplifying systems for Vamplifying modulated Waves, and more particularly to such systems which operate at comparatively high power and/or high efficiency and which are intended to give a so-called linear amplification of the modulated Wave.
  • linear amplification of a modulated Wave is meant an amplification which introduces substantially no distortion ofthe modulation envelope regardless of whether or not some distortion of the carrier wave may be introduced.
  • linear amplification of a modulated wave is such an amplification that the resul-ting output wave has an envelope of the same wave form as the envelope of the input wave, although the wave form of the individual carrier undulations may perhaps be slightly distorted from that of the input wave.
  • the ordinary linear amplier used in many radio broadcast transmitters is essentially a tuned amplifier biased approximately to cut-ofi' and operated under conditions such that the amplitude of the voltage developed in the output tank cir.- cuit is substantially proportional to the amplitude of the voltage exciting the amplifier.
  • the ordinary linear amplier used in many radio broadcast transmitters is essentially a tuned amplifier biased approximately to cut-ofi' and operated under conditions such that the amplitude of the voltage developed in the output tank cir.- cuit is substantially proportional to the amplitude of the voltage exciting the amplifier.
  • the novel method of my invention comprises detecting some of the input energy to the amplifier as well as some of the output energy from the amplifier to obtain two diiferent waves of envelope frequency, which respectively represent the wave forms of the envelopes of the input to the amplifier and the output from the ampliiier.
  • these two envelope-frequency waves are then mutually opposed to yield a corrective control wave corresponding to the difference between them, which difference represents the distortion of the envelope which has been introduced by am; plification.
  • This control wave so derived is then used to modulate the ⁇ amplifier in such sense as to tend to reduce the differences between the' two detected waves, i. e. as to tend to reduce distortions in the envelope which are introduced by the amplifier.
  • this method has some points of resemblanceto the so-called negative feedback system as applied to modulators, wherein a modulator, alone or in cascade with preceding and/or succeeding amplifier stages, is controlled to reduce distortion in its output envelope by detecting its output and feeding such detected wave back to the speech frequency input channel in negative feedback fashion.
  • the present invention may in certain applications be employed instead of the above outlined negative feedback system with very considerable advantage from the standpoint of simplicity and convenience of adjustment, and in certain other types of systems the present invention may be used in conjunction with the aforesaid principle of negative feedback of envelope frequencies in order to yield a complete combined system which shall be superior to such a system employing the negative feedback arrangement alone.
  • Fig. 1 illustrates the fundamentals of the system and method of my invention
  • Fig. 2 illustrates in greater detail a ⁇ circuit embodying the invention
  • Fig. 3 is a representation of a series of curves useful in understanding the principles of operation of the invention.
  • i Figs. 4, 5 and 6 illustrate modified circuits embodying the invention.
  • a roughly linear amplifier I is fed with an input of modulated carrier over an input channel 2, and delivers a corresponding amplified output wave to an output channel 3.
  • a small portion of the input signal to the amplifier is, in accordance with the present invention, rectified by a linear rectifier 4; and the output of this rectifier 4 is balanced against a corresponding output of another linear rectifier 5 which is excited from the amplifier output.
  • the output voltages of these two rectifiers may be made such that they would be identical if the amplifier I, were operating without distortion, and there would then be no difference voltage obtained when the rectifier outputs are balanced against each other.
  • VAV circuit arrangement' which embodies the fundamental system indicated'schematically in Fig. i1 "is illustrated in"Fig. 2.
  • Here-T1 represents a class rB:or B-eC amplifier with an input tank circuit I oCn'which'- is fed inductively from input Winding L and With an input bias source Ec.
  • This tube delivers its output to tank circuit L1C1, to which'a 'suitable loadv (not shown) is coupled.
  • To'prevet singing or instability suitable neutralizationcircuits .of rknown Ytype are preferably employed. Such circuits are omitted from the dawin'gs'for the sake Vof Ysimplification butY may be assumed to be included not only in Fig. 2 now under consideratiombut also in Figs.
  • Fig. 3 Some of' the details of operation of the arrangement shown in Fig. 2 aregiven in Fig. 3.
  • the modulated wave applied to the'input of the triode amplifier has the character shown at a, while curve b shows the ⁇ modulation envelope ofthe output wave that would be obtained in normal operation under conditions such that the positive peaks of modulation were somewhat flattened.
  • Curves c and d illustrate the corresponding audio voltages developed in the outputs ofv rectiiiers T2 and T3. When these are balanced against each other it will be noted that the'distortion produced by the amplier results in a difference voltage that is shown, in curve e.
  • I utilize this difference voltage to modulate the amplifier in such a way as to tend to increase the total amplifier output at the peak of modulation, and thereby compensate for the distortion of the amplifier.
  • the system operates by introducing, through modulation, a compensating distortion in the amplifier that tends to counteract the distortion that would otherwise be present.
  • Fig. 4 differs from Fig. 2 principally in that the unbalance in the output of the rectiers is amplified before being applied to amplifier I to modulate this amplifier. This has the advantage of making available an increased amount of modulating power.
  • Fig. 5 the compensating distortion is introduced into the amplifier I by plate rather than grid modulation.
  • a center-tapped-transformer type of push-pull amplifier output is used in balancing the rectifier outputs after amplification thereof.
  • the systems of Figs. 4 and 5 are similar to that of Fig. 2. The operation will be self-evident in comparison with the foregoing description of the operation of Figs. 1 and 2.
  • Fig. 6 shows the system applied to a two-stage amplifier, with the distortion-correcting modulation introduced into the first stage.
  • the second stage T1 of the amplifier introduces the greater part of the distortion, the first stage T then serving to correct the distortions of T1.
  • the method that I have described for correcting distortion introduced by amplifiers makes it possible not only to increase the linearity obtainable, but particularly to select operating conditions particularly favorably from the point of View of efficiency and power output, but Which would ordinarily be accompanied by excessive distortion.
  • the amplifieigor at least the last stage thereof may be biased to or even beyond cut-off and/or the tank circuit impedance and magnitude of the impressed modulated signal may be chosen to give better output and efficiency than would ordinarily be possible where the amplifier tube itself must be distortion free.
  • the method and system for producing substantially linear amplification in accordance with my invention presents another very important advantage in that the two detectors Vwhose outputs are to be compared tend to mutually compensate any non-linearities which may exist in the detectors. It is particularly advantageous to make the two detectors 4 and 5 alike so far as practicable, or at least similar in characteristics. WhenY this is done it is not necessary that the individual 'characteristics of the detectors be linear since distortions arising in one of these detectors are balanced by the corresponding distortions in the'other detector. vThis feature of mutually compensating detector distortions represents a further advantage of the method and system of my invention as compared to thev known method of negative feedback of envelope frequencies, since it is much less difficult to make two rectifiers similar in characteristics than to make one rectifier perfectly linear.
  • the linear amplifying system of my invention is particularly useful in cases where it is desired to increase the power of an existing transmitter by adding thereto a further high-power, highefiiciency linear amplifying system, and employing the existing transmitter to excite such a further amplifying system.
  • a further high-power, highefiiciency linear amplifying system and employing the existing transmitter to excite such a further amplifying system.
  • my invention vit is possible to provide such an amplifying system which may be added as a separate totally independent unit.
  • the linear vamplifying system of myinvention when excited by an existing transmitter as above described will yield, Without doing anything Whatsoever to the original transmitter, all the advantages which could be realized by modifying the combination. of transmitter and amplifier so as to apply the known arrangement of negative feedback previously referred to.
  • the method of linearly amplifying a modulated input wave so as to produce a modulated output wave of greater power which comprises detecting a portion of said input wave to produce a modulation envelope wave, non-linearly amplifying another portion of said input wave to produce an amplified wave, detecting a portion of said amplified Wave to produce a second envelope wave, delivering another portion of said amplified wave as said desired output wave, deriving the difference wave of said two detected portions, segregating the alternating component of said Cil.
  • the method of controlling an inherently non-linear amplifier having at least one vacuumtube amplifying stage biased for high efficiency and non-linearity of amplification so as to produce from a 4low-power modulated high-frequency input wave a desired high-power modulated high-frequency output wave of substantially the sameenvelopewave-form which comprises detecting one portion of said input wave to produce a modulation envelope wave, applying another portion of said input wave to said nonlinear amplifier, deriving from said amplifier an amplified wave, detecting a portion of said amplified wave to produce a second modulation envelope wave, comparing said two detected por- ⁇ tions to derive a difference wave therefrom, segregating the alternating components of ⁇ said different waves, modulating said amplifier in accordance with said segregated component and delivering the remainder of said derived amplified wave as the desired high-power output wave.
  • Anamplifying system for linearly amplifying a modulated input wave comprising an inherently non-linear amplifier having an input circuit andan output circuit, means for detecting Va portion of said modulated input wave'to obtain an input modulation envelope wave, means for impressing another portion of Said modulated input wave on said input circuit, means for deriving from said output circuit an amplified modulated wave, means for detecting a portion of said amplified modulated wave to produce an output modulation envelope wave, and means for modulating said amplifier with an alternating wave corresponding to the alternating component of the difference between said detected portion of said modulated input wave and said detected portion of said amplified modulated wave.
  • said inherently non-linear amplifier comprises a plurality of stages in cascade at least the last stage being non-linear
  • said means for modulating said amplifier in accordance with the difference between the detected portions comprises means for deriving a control wave corresponding to the difference between said detected portion of the modulated input wave and said detected portion of the amplified modulated wave, means for segregating the alternating component of said derived wave, and means for applying said segregated component to a stage preceding said last stage.
  • said means for detecting Ia portion of said input wave and said means for detecting a portion of said amplified wave each comprise a somewhat non-linear detecting element, and wherein said two elements have similar characteristics whereby the non-linearity of one of said elements is compensated by the similar nonlinearity of the other of said elements.
  • said means for modulating said amplifier in accordance with the difference between said two detected portions of' waves comprises means for balancing said detected portion of the modulated input wave against said detected portion of the amplified modulated Wave to derive a difference wave corresponding to the difference between said detected portionsgmeans for segregating the alternating component of said difference wave, means for amplifying said alternating component, and means for applying said amplified alternating component to said amplifier to vary the output thereof.
  • said means for modulating said ampliiier in accordance with the difference between said two detected portions of waves comprises means for amplifying said detected portion of the modulated input Wave, means for amplifying said detected portion of the amplified modulated wave, means for balancing said amplied detected portion of the modulated input wave against said amplified detected portion of the amplified modulated wave to derive a diierence Wave corresponding to the difference between said amplified detected portions, means for segregating the alternating component of said difference wave and means for applying said alternating component to said amplier to vary the output thereof.
  • An amplifying system for linearly amplifying a modulated input wave comprising an amplier whichv includes at least one discharge tube having cathode and grid and anode electrodes, means for biasing said electrode to such potentials'that the eiiiciency of the tube is high but its amplication is non-linear, means for applying a portion of said modulated input wave to said grid electrode, ⁇ means for deriving-an amplified modulated wave 'from said anode electrode, a rst detector connected to detect another portion of said modulated input wave to drive an input modulation envelope wave, a second detector connected to detect a portionY of said amplified modulated wave to derive an output modulation envelope wave, means for deriving an alternating control Wave corresponding to the difference between alternating components of said detected portions of the input and amplified waves, means for applying said control wave to at least one discharge tube of said amplifier to vary said amplified modulatedV wave, whereby the wave-form of the envelope of said amplified wave is rendered substantially the same as
  • An amplifying system wherein said amplier includes a plurality of discharge tubes connected successively in cascade, the tube whose electrodes are biased to nonlinear yamplification by said means for biasing being the last tube of said successive cascade, and wherein said means for applying said control wave to at least one discharge tube of said amplier is connected to apply such control wave to a preceding tube of said successively connected plurality of tubes.

Landscapes

  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Amplifiers (AREA)
US273404A 1939-05-13 1939-05-13 Linear amplifying system Expired - Lifetime US2252049A (en)

Priority Applications (5)

Application Number Priority Date Filing Date Title
BE474454D BE474454A (en, 2012) 1939-05-13
US273404A US2252049A (en) 1939-05-13 1939-05-13 Linear amplifying system
GB3871/40A GB537558A (en) 1939-05-13 1940-03-01 Linear thermionic amplifying systems
FR865592D FR865592A (fr) 1939-05-13 1940-05-11 Systèmes amplificateurs d'ondes électriques
ES176812A ES176812A1 (es) 1939-05-13 1947-02-15 Mejoras en sistemas amplificadores de características lineal

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US273404A US2252049A (en) 1939-05-13 1939-05-13 Linear amplifying system

Publications (1)

Publication Number Publication Date
US2252049A true US2252049A (en) 1941-08-12

Family

ID=23043798

Family Applications (1)

Application Number Title Priority Date Filing Date
US273404A Expired - Lifetime US2252049A (en) 1939-05-13 1939-05-13 Linear amplifying system

Country Status (5)

Country Link
US (1) US2252049A (en, 2012)
BE (1) BE474454A (en, 2012)
ES (1) ES176812A1 (en, 2012)
FR (1) FR865592A (en, 2012)
GB (1) GB537558A (en, 2012)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2567272A (en) * 1946-06-27 1951-09-11 Hartford Nat Bank & Trust Co Circuit arrangement for protecting an amplifying tube against overloading
DE950788C (de) * 1954-01-09 1956-10-18 Telefunken Gmbh Senderschaltung zur Amplitudenmodulation einer Hochfrequenzschwingung mit herabgesetzter Bandbreite
US2807665A (en) * 1952-08-09 1957-09-24 Perlman Robert Ruben Reduction of distortion in amplifying systems
US2960660A (en) * 1957-06-07 1960-11-15 Lenkurt Electric Co Inc Feedback amplifier circuit
US3335370A (en) * 1965-03-31 1967-08-08 Trw Semiconductors Inc High level amplitude modulation of transistor radio frequency amplifiers
DE1278562B (de) * 1960-09-22 1968-09-26 Philips Nv Schaltungsanordnung zur Linearisierung der Amplitudenkennlinie eines Leistungsverstaerkers

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3525052A (en) * 1968-05-13 1970-08-18 Farnsworth D Clark Distortion cancelling circuit for amplifiers

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2567272A (en) * 1946-06-27 1951-09-11 Hartford Nat Bank & Trust Co Circuit arrangement for protecting an amplifying tube against overloading
US2807665A (en) * 1952-08-09 1957-09-24 Perlman Robert Ruben Reduction of distortion in amplifying systems
DE950788C (de) * 1954-01-09 1956-10-18 Telefunken Gmbh Senderschaltung zur Amplitudenmodulation einer Hochfrequenzschwingung mit herabgesetzter Bandbreite
US2960660A (en) * 1957-06-07 1960-11-15 Lenkurt Electric Co Inc Feedback amplifier circuit
DE1278562B (de) * 1960-09-22 1968-09-26 Philips Nv Schaltungsanordnung zur Linearisierung der Amplitudenkennlinie eines Leistungsverstaerkers
US3335370A (en) * 1965-03-31 1967-08-08 Trw Semiconductors Inc High level amplitude modulation of transistor radio frequency amplifiers

Also Published As

Publication number Publication date
GB537558A (en) 1941-06-26
FR865592A (fr) 1941-05-27
ES176812A1 (es) 1947-03-16
BE474454A (en, 2012)

Similar Documents

Publication Publication Date Title
US2220201A (en) Modulation
US2343207A (en) Wave translation device
US2252049A (en) Linear amplifying system
US2346020A (en) Modulation amplifier and modulator
US3274492A (en) Transmitting device for the transmission of amplitude-modulated oscillations
US2554132A (en) Amplifier circuit
US2172453A (en) Radio transmitter
US2379513A (en) Electronic amplification
US2198464A (en) Distortion reducing circuit
US3002161A (en) Transmitter
US2270012A (en) Distortion reducing circuits
US2446025A (en) Modulation system
US2346545A (en) Electron discharge device circuit
US2176587A (en) Method of and means for modulating wave energy
US2182790A (en) Distortion reducing system for gridmodulated amplifier
US2133410A (en) Distortion reducing system in modulated amplifiers
US1999190A (en) Electrical circuits
US2288275A (en) Modulating system
US2076787A (en) Variable carrier system
US2159020A (en) Modulating system
US2267703A (en) Modulation
US2079444A (en) Operating point control for thermionic devices
US2135198A (en) Transmitter modulation
US2066970A (en) Controlled carrier wave system for signaling
US2491107A (en) Thermionic valve circuits