US2188671A - Wave amplifying system - Google Patents

Wave amplifying system Download PDF

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Publication number
US2188671A
US2188671A US198619A US19861938A US2188671A US 2188671 A US2188671 A US 2188671A US 198619 A US198619 A US 198619A US 19861938 A US19861938 A US 19861938A US 2188671 A US2188671 A US 2188671A
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US
United States
Prior art keywords
amplifier
feedback
gain
path
transmission
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
US198619A
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English (en)
Inventor
Ira G Wilson
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.)
AT&T Corp
Original Assignee
Bell Telephone Laboratories Inc
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
Application filed by Bell Telephone Laboratories Inc filed Critical Bell Telephone Laboratories Inc
Priority to US198619A priority Critical patent/US2188671A/en
Priority to GB2892/39A priority patent/GB524340A/en
Priority to NL55159D priority patent/NL55159C/xx
Priority to FR852274D priority patent/FR852274A/fr
Application granted granted Critical
Publication of US2188671A publication Critical patent/US2188671A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B3/00—Line transmission systems
    • H04B3/02—Details
    • H04B3/04—Control of transmission; Equalising
    • H04B3/10—Control of transmission; Equalising by pilot signal
    • H04B3/12—Control of transmission; Equalising by pilot signal in negative-feedback path of line amplifier
    • 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
    • H03G—CONTROL OF AMPLIFICATION
    • H03G1/00—Details of arrangements for controlling amplification
    • H03G1/0005—Circuits characterised by the type of controlling devices operated by a controlling current or voltage signal
    • H03G1/0035—Circuits characterised by the type of controlling devices operated by a controlling current or voltage signal using continuously variable impedance elements
    • H03G1/0041—Circuits characterised by the type of controlling devices operated by a controlling current or voltage signal using continuously variable impedance elements using thermistors
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03G—CONTROL OF AMPLIFICATION
    • H03G3/00—Gain control in amplifiers or frequency changers
    • H03G3/02—Manually-operated control
    • H03G3/04—Manually-operated control in untuned amplifiers
    • H03G3/06—Manually-operated control in untuned amplifiers having discharge tubes
    • H03G3/08—Manually-operated control in untuned amplifiers having discharge tubes incorporating negative feedback

Definitions

  • This invention relates to wave amplifying systems, as for example, vacuum tube amplifiers.
  • Objects of the invention are to control transmission properties of such systems, for example, 5 gain and distortion introduced by the, systems, to facilitate application of feedback in the systems, and to reduce singing tendency ormaintain proper. margin against singing in the systems.
  • the invention- is applied to an amplifier with a forwardly transmitting, wave amplifying portion and a feedback path from the output to the input of the amplifying portion for producing negative or gain-reducing feedback around the amplifying portion, for ex,- ample, to stabilize the gain or reduce the modulation introduced by the amplifier, in accordance with the principles described by H. S. Black in his article entitled Stabilized feed-back ampli bombs, Bell System Technical Journal, January 0 1934, and in his Patent 2,102,671, Decembery2l,
  • the gain of such/an amplifier varies substantially as the loss in the feedback path, and is substantially independent of the amplification ratio or transmission efl'iciency of the amplifying portion. It is usual to control the amplifier gain for any given frequency by changing the loss in the feedback path for such frequency.
  • a feature of thepresent invention is provision of means for stabilizingthe amount of. feedback or the loop gain, fora given frequency, against variation due to change produced in transmission efficiency of the feedback path. For; eX-- ample, such change may be a given decreasemade in the transmission efiiciency of the feedback path in order to increase the gain of the amplifier,
  • operation of the loop gain stabilizing means may increase the transmission eiliciency of the amplifying portion of the amplifier substantially the given amount in order to reduce variation of the loop gain or maintain the amount of feedback substantially unchanged, as for example, to maintain the feedback at the maximum value that is permitted by the required margin against singing; or the change in the transmission efficiency of the feedback path may be a given increase made in order to decrease the gain of the amplifier, and then operation of the loop gain stabilizing means may insure decrease of the 5 transmission efficiency of the amplifying portion of the amplifier substantially the given amount in order to reduce variation of the loop gain or maintain the loop gain substantially unchanged, for instance at the maximum value that is per- 10 mitted by the required singing margin.
  • the inverse or complementary changes in transmission efiiciency of the feedback path and transmission efficiency of the amplifying portion of the amplifier may be made autol5 matically, as for example by a pilot wire or pilot channel gain control or an automatic volume control.
  • the automatic gain control may vary the temperature (and thereby the resistance) of a heat responsive resistance (ther-- 2 0 mistor), for instance a silver sulphide resistor in a shunt arm of the feedback path, and the tem- 'perature (and thereby the resistance) of a silver I sulphide resistor in series in the grid-cathode.
  • FIGs. 1 and 2 show circuit diagrams of two forms of the invention.
  • the amplifier of Fig. 1 may be a stabilized feed- 35.
  • back amplifier of the general type disclosed, for example, in the above-mentioned patent and published article. It comprises an amplifying path or element shown as including tandem connected vacuum tubes l and 2 and interstage and output circuit 3 which may include one or more stages of vacuum tubes. It also comprises a feedback path 1 shown as including a transmission control network. N.
  • the amplifying path or element that is, the forward path including thev elements 5 l 2 and 3, may be referred to as the circuit and the feedback path may be referred to as the B-circuit, the significance of ,u, ,3, .a-Cll'Cllil? and ,c-circuit being as indicated in the patent and.
  • the network 50 N may be referred to as the ,B-circuit network.
  • the quantity s, the propagation around the closed feedback loop, or the modification that a voltage undergoes in transmission once around the closed feedback loop, may be large compared 55 to unity, as for example of the order of- 50 or and 1,, the propagation of the forwardly transmitting path, may be large compared to ,s, the propagation of the feedback path.
  • the network N may be any suitable transmission control network, for example for amplitude or phase equalization or correction of distortion in the general manner disclosed in the patent and published article just mentioned.
  • it may be a transmission equalizing network such as network 374 in Fig. 65 of that patent or in Fig. 4 of H. S. Black Patent 1,956,547, May 1, 1934, or network 14 of F. A. Brooks Patent 2,075,975, April 6, 1937, network N of E. B. Payne Patent 2,075,956, April 6,1937, or network 27 of R. W. Chesnut Patent 2,154,062.
  • the amplifier receives wavesfrom an incoming line or circuit 5 terminated in amplifier input transformer 6 and transmits the amplified, Waves to outgoing line or circuit I.
  • the circuits 5 and I may be, for example, sections of a multiplex carrier cable or open wire circuit.
  • the amplifier may amplify simultaneously the waves of a number of carrier telephone or telegraph channels, or both, extending over a wide frequency range.
  • the interstage circuit coupling tubes I and 2 comprises interstage network 8 and a shunt arm or branch including a thermistor or thermosensitive element 9, as for example a silver sulphide resistor. Associated with resistor 9, but electrically insulated therefrom, is a heating element I0 therefor.
  • The'feedback path 1 comprises a shunt arm including a resistor IE and comprises a series arm including a thermosensitive element I2, as for instance a silver sulphide resistor. Associated with resistor I2, but electrically insulated therefrom, is a heating element I3 therefor. Elements 9 and I9 are shown in a heating chamber, I4; and elements I2 and I3 are shown in a heating chamber '15.
  • pilot control 2I is, as usual, responsive to resistance changes in a pilot wire or loop circuit, indicated by pilot conductors 25, which may be, for example, a pair 1 of wires that is included in the same lead cable sheath as the signal conductors such as 5 and extends over the length of the line section assigned to the amplifier and is subject to the same temperature variations as the signaling conductors.
  • increase of attenuation of the line 5 and the pilot wireloop circuit 25 causes the control 2
  • the increase of resistance I2 increases the loss or reduces the transmission efficiency of the feedback path I or the ,B-circuit of the amplifier, or in other words reduces the magnitude of B, and thereby increases the amplifier gain to compensate for the increased attenuation of line 5 caused by the increase of temperature of the line and thus maintain a constant transmission equivalent for the line and amplifier; and the increase of resistance 9 decreases the lossor increasesthe amplification of the, forward path or l-circuit of the amplifier, pref-.
  • the deleterious phase shift outside of the used frequency band may be annulled at the same time that resistance 9 is varied when obtaining the desired amplifier gain settings in the used frequency band.
  • gain and phase around the over-all feedback I loop may tend to'change materially.
  • impedance Z' connected across resistance 9 compensatory and opposite change of phase shift, as well as of gain, can be introduced by 9 in transmission through the -circuit, that is the forward path of the amplifier.
  • the 8 gain and phase shift i. e., the gain and phase shift around the over-all feedback loop
  • I2 I2
  • the networks Z and Z may be designed to give constant loop phase shift, i. e;,
  • the control 2I may be of any suitable type.
  • it may be of the general typedisclosed in Mallinckrodt Patent 2,098,968 November 16, 1937; or the controlZI maybe, for example, a power source and a heater current ad 1 justing rheostat such as the power source and 1 the heater current'adjustin pilot apparatus controlled rheostat T of Fig.3 of E. I. GreenPatent 1,918,390, July 19, 1933, and'a pilot wire trans-' mission regulator control equipment for operating the rheostat, suchiasthat which operates the gain adjusting rheostat 12 of the above-mentioned H. S. Black Patent 1,956,547.
  • the control 23 may be of any suitable type.
  • it may be of the. type disclosed in the above-mentioned E. 1.
  • Green Patent 1,918,390 or of the type disclosed in R. 'W. Chesnut Patent "2,154,062, April ll 19s9;- or mmay be -of the type disclosed in Fig. 2 of H. S. Black Patent 2,154,888, April-18, 1939.
  • H I I The energizing circuits such as the plate current supply-, grid biasing and cathode heating circuits for the amplifier are omitted from the drawing in the interest of simplicity-as they may be of any usual or suitable type.
  • FIG. 2 shows a modification of the circuit of Fig. 1 in which theamplifier gain control resistor iS'fl resistor l2 in a shuntarm of the p-circuit or feedback path, and in whichthe rethereby controlling the gain of thestage comprising this tube.
  • I Y theamplifier gain control resistor iS'fl resistor l2 in a shuntarm of the p-circuit or feedback path
  • a resistor I 3' in a heating chamber 15 with resistor I 2- acts as a heating element therefor.
  • a resistor It in a heating chamber M' with resistor 9 acts as a heating element therefor.
  • ments l2 and 9' have negative temperature coefficients of resistance, increase of the line attenuation should be accompanied byincrease of the current transmitted to the. heaters l3" and Ill, for decreasing the resistances of elements l2 and 9' simultaneously and thereby maintaining the magnitude of s constant and maintaining the transmission equivalent of the line and amplifier constant.
  • the control M maybe of any suitable type.
  • it may be of the type disclosed in the above-mentioned Mallinckrodt'Patent 2.698,-
  • the method of operating on a negative feedback amplifier which comprises changing the over-all amplifier gain and making the magnitude and frequency variations of the gain around the feedback loop the same for the changed overall gain as for the original over-all gain.
  • a negative feedback amplifier with means for changing the transmission efficiency of the feedback path at a given frequency, and means whose operation insures change of the transmission efficiency of the forward path, around which the feedback path is connected, inversely and by ⁇ 59 substantially the same amount.
  • a negative feedback amplifier comprising means for changing the over-all amplifier gain whose operation tends to change the'feedback
  • a negative feedback amplifier with meansto increase the transmission efficiency of the feedback path for reducing the amplifier gain, means to correspondingly decrease the transmission efficiency of the forward path around which the feedback path is connected and thereby make the magnitude and frequency variation of the gain around the feedback loop the same as before said increase'and decrease, and means comprising common operating means for said two first-mentioned means for causing said increase and said decrease to take place together.
  • a negative feedback amplifier with gain control means comprising a temperature dependent impedance in the feedback path, transmission efficiency control means comprising a temperature dependent impedance in the forward path around which the feedback path is con- .nected, and means coordinately controlling the temperatures of said impedances and thereby causing variation of their impedance values that produces substantially equal but inverse changes in the transmission efficiencies of said paths.
  • a negative feedback amplifier with gain control means comprising a'heat-responsiveresistor in the feedback path and transmission control means comprising amplifier comprising a forward amplifying path and a feedback path connected around said forward path for producing negative feedback in 1 said amplifier, a silver sulphide resistor in a shunt arm of said feedback path, means for varying the transmission 'efilciency of said forward, path without materially affecting the transmission efiiciency of said feedback path including a silver sulphide feedback resistor producing ina portion of said forward path negative feedback that increases with increase'of the resistance of said feedback-resistor, current responsive means for heating said resistors, and an automatic gain regulator control circuitfor supplying said curn -10 gain control system, an automatic gain regulator control circuitfor supplying said curn -10 gain control system
  • an automatic amplifier comprising a forward amplifying path and a feedback path connected around said for ward path for producing negative feedback in said amplifier, a silver sulphide resistor in a series arm of said feedback path, means for varying the transmission eificiency of said forward path without materially affecting the transmission efficiency of said feedback path'including a silver sulphide resistor in a shunt arm of said forward; path, current responsive means for heating said resistors, and an automatic gain regulator coni trol circuit for supplying said current.
  • the method of operating a negative feedback amplifier having the transmission efiiciency of the feedback path vary over. a range of fre- I quencies, which comprises changing the transmission efficiency and the phase shift of the feed- 7 back path at frequencies in said. range and rendering the transmission efiiciency and the phase shift around the feedback loop under the changed condition substantially the same as before said change bycompensatory"substantially equal but inverse change in the transmission efiiciency and the phase shift of the forwardpath around which the feedback path is connected.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Amplifiers (AREA)
US198619A 1938-03-29 1938-03-29 Wave amplifying system Expired - Lifetime US2188671A (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
US198619A US2188671A (en) 1938-03-29 1938-03-29 Wave amplifying system
GB2892/39A GB524340A (en) 1938-03-29 1939-01-27 Thermionic valve and like wave amplifying systems
NL55159D NL55159C (hu) 1938-03-29 1939-02-15
FR852274D FR852274A (fr) 1938-03-29 1939-03-28 Systèmes amplificateurs d'ondes électriques et analogues

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US198619A US2188671A (en) 1938-03-29 1938-03-29 Wave amplifying system

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US2188671A true US2188671A (en) 1940-01-30

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US198619A Expired - Lifetime US2188671A (en) 1938-03-29 1938-03-29 Wave amplifying system

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US (1) US2188671A (hu)
FR (1) FR852274A (hu)
GB (1) GB524340A (hu)
NL (1) NL55159C (hu)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2567824A (en) * 1947-03-18 1951-09-11 Bell Telephone Labor Inc Automatic gain control
US2570294A (en) * 1945-06-02 1951-10-09 Int Standard Electric Corp Frequency selective network arrangement
US2592738A (en) * 1945-09-19 1952-04-15 Us Navy Electronically controlled low impedance phase shifting device
US3062994A (en) * 1960-01-19 1962-11-06 Gilbert & Barker Mfg Co Electronic level sensing servosystem
US3105942A (en) * 1958-12-12 1963-10-01 Philips Corp Automatic gain control amplifier system

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2570294A (en) * 1945-06-02 1951-10-09 Int Standard Electric Corp Frequency selective network arrangement
US2592738A (en) * 1945-09-19 1952-04-15 Us Navy Electronically controlled low impedance phase shifting device
US2567824A (en) * 1947-03-18 1951-09-11 Bell Telephone Labor Inc Automatic gain control
US3105942A (en) * 1958-12-12 1963-10-01 Philips Corp Automatic gain control amplifier system
US3062994A (en) * 1960-01-19 1962-11-06 Gilbert & Barker Mfg Co Electronic level sensing servosystem

Also Published As

Publication number Publication date
FR852274A (fr) 1940-01-27
GB524340A (en) 1940-08-05
NL55159C (hu) 1943-04-15

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