US2527406A - Anode and grid bias voltage system for class b or c amplifiers - Google Patents

Anode and grid bias voltage system for class b or c amplifiers Download PDF

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Publication number
US2527406A
US2527406A US668424A US66842446A US2527406A US 2527406 A US2527406 A US 2527406A US 668424 A US668424 A US 668424A US 66842446 A US66842446 A US 66842446A US 2527406 A US2527406 A US 2527406A
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United States
Prior art keywords
voltage
anode
transformer
grid
load
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US668424A
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English (en)
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Donker Pieter Adriaan
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Hartford National Bank and Trust Co
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Hartford National Bank and Trust Co
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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
    • H03F3/20—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
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05F—SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES
    • G05F1/00—Automatic systems in which deviations of an electric quantity from one or more predetermined values are detected at the output of the system and fed back to a device within the system to restore the detected quantity to its predetermined value or values, i.e. retroactive systems
    • G05F1/10—Regulating voltage or current 
    • G05F1/46—Regulating voltage or current  wherein the variable actually regulated by the final control device is DC
    • G05F1/52—Regulating voltage or current  wherein the variable actually regulated by the final control device is DC using discharge tubes in series with the load as final control devices
    • 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
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N5/00—Details of television systems
    • H04N5/04—Synchronising
    • H04N5/08—Separation of synchronising signals from picture signals

Definitions

  • the invention relates to a push pull amplifying system wherein such a negative bias voltage is supplied to the control grids of the amplifying tubes that in uncontrolled condition the anode current of the amplifying tubes is substantially suppressed (B-class amplifier) or wherein use is made of a larger grid bias voltage-than is required for the suppression of the anode current (C-class amplifier).
  • the required grid bias voltage which increases with the control of the amplifier is obtained by connecting an impedance into the output circuit of the amplifier, by rectifying that portion of the output energy which is taken therefrom and by supplying the load-dependent direct-current voltage thus obtained, after being smoothed, to the control grids.
  • variable grid bias voltage from the anode direct-current voltage itself, in which event the grid bias voltage is o'ctained by rectifying and smoothing the oscillations of an auxiliary oscillator whose anode voltage is formed by that of the amplifying tubes.
  • the last-mentioned method of generating the variable grid-bias voltage has the advantage that now the energy required therefor is taken, in contradistinction to the first-mentioned method, directly from the anode voltage apparatus, the last-mentioned method has the drawback of being comparatively complicated and expensive.
  • the invention aims at avoiding the abovementioned drawbacks.
  • variable gridbias voltage is obtained by rectifying and smoothing. an alternating current or voltage which occurs in the anode-voltage apparatus and which depends on the control of the amplifier.
  • variable grid-bias. voltage is preferably taken from the secondary winding of a transformer whose primary winding is connected in series with the anode'woltage winding of the supply transformer whilst, in order to reduce the voltage drop thus produced in the anode voltage drop produced across rectifier circuit, the ratio of transformation of the transformer is so chosen, that the voltage the primary windings thereof is smallwith respect to the output voltage.
  • the, for example, low-frequency oscillations to be amplified are supplied to the input terminals l of a preamplifier 2 whose output circuit comprises a transformer: 5.
  • This transformer has a secondary winding e which is divided, into two equal parts which are connected into the control-grid circuits of two amplifying tubes 5 and 6 respectively which are connected in push-pull and as B- class.
  • the amplified oscillations are supplied to the load impedance formed, for example, by a loudspeaker 8.
  • the anode voltages of the amplifying tubes 5 and 6 are taken from an anode voltage apparatus which com-prises a supply transformer 51 which is to be connected to an alternating current supply, a full-wave rectifying tube it and a smoothing filter-consisting of condensers l l and a choke coil l2.
  • the negative and. positive output terminals I3 and [4' respectively of the anode-voltage apparatus are connected to the earthed cathodes of the amplifying tubes 5 and 6 and to the central tap on the primary winding of the output transformer 1 respectively.
  • variable negative gridbias voltage required for the tubes 5, B connected as a B-class rectifier is taken from the alternating current supply with the aid of an additional supply transformer 15 and after being rectified by a full-wave rectifying tube t6 and smoothed by means of a filter l1, it is supplied via the halves of the secondary winding of the input transformer 3 to the control grids of the amplifying tubes.
  • control grids have supplied to them not only the fixed negative bias voltage taken from the transformer IE but also a variable bias voltage which counteracts the said fixed negative bias and which increases with the load on the anode voltage apparatus and therefore with the control of the push-pull amplifier.
  • variable bias voltage is derived from an alternating current or voltage which occurs in the anode-voltage apparatus and which increases with the load on this apparatus.
  • the variable grid voltage may be taken from the choke coil by providing a secondary winding on the core of the said coil and by supplying the alternating voltage occurring across the said winding, after being rectified and smoothed, to the control grids of the tubes.
  • variable bias voltage is taken from the secondary winding of a transformer I8 whose primary winding I8 is connected between the two halves 20 and 2I in which the secondary winding of the supply transformer 9 is divided in view of the full-wave rectifier I whilst the central tap on the primary winding I9 forms the negative output terminal of the anode-voltage apparatus.
  • the primary winding I9 passes consequently the anode current of the rectifying tube III, which current increases with the increasing load on the anodevoltage apparatus.
  • the resulting alternating voltage set up across the rectifying tube I6 has a maximum instantaneous value which decreases with an increasing load on the anode-voltage apparatus with the result that with an increasing load on the anode-voltage apparatus the negative grid bias voltage supplied to the first smoothing condenser 25 of the filter I! and consequently to the control grids of the tubes 5 and 6 decreases owing to the increasing control of the push-pull amplifier, which result was aimed at.
  • the output voltage of the filter I1 is supplied, via potentiometers 28 and 29 respectively and after being further smoothed with the aid of condenser 30 and 3I respectively, to the control grid concerned.
  • the voltagev drop occurring in the primary winding I9 is preferably reduced as far as possible.
  • a supplementary advantage of the above-mentioned increase of the negative grid-bias voltage upon the occurrence of grid current is that thus the production of an inadmissibly high anode current in the tubes 5 and 6 is counteracted.
  • the transformer I8 In order to prevent the tubes 5 and 6 from being overloaded, it has furthermore proved to be advantageous to dimension the transformer I8 from which is taken that part of the total gridbias voltage which varies with the load, in such manner that with the highest admissible load on the amplifying tubes 5 and 6 the iron of the core of the transformer I8 just gets saturated. Upon an increase of the load above the highest admissible load on the amplifying tubes 5 and 6 the absolute value of the grid-bias voltage no longer decreases with the result that a further increase of the anode current of the tubes 5 and 6 is not supported.
  • tubes 5 and 6 are represented as triodes.
  • the invention may, however, also be applied, of course, to tubes having more than three electrodes and the effect aimed at may also be obtained by supplying the variable grid-bias voltage to auxiliary grids instead of to the control grids.
  • fullwave rectifier systems for generating the anode and grid-bias voltages is not essential for the invention although, in view of the smoothing of the rectified alternating voltages, this is to be preferred to the use of half-wave rectifier systems.
  • a system for supplying anode and grid bias voltages to an electronic amplifier of the class B or C type comprising a first direct voltage supply energized from an alternating voltage source and furnishing anode potential to said amplifier, said amplifier acting as a load on Said first supply, a second voltage supply furnishing constant grid bias potential to said amplifier, means for deriving an auxiliary alternating voltage from said first supply varying in accordance with changes in the load thereon, means to rectify and filter said auxiliary voltage to produce a control voltage whose magnitude depends on the changes in the load imposed on said first supply, and means for combining said control voltage with said constant grid bias potential to produce a resultant grid bias varying inversely as the load.
  • a system for supplying anode and grid bias voltages to an electronic amplifier of the class B or C type comprising a first voltage supply furnishing anode potential to said amplifier, said amplifier acting as a load on said first supply, said first supply including a transformer having a primary winding for connection to an alternating voltage source and a secondary Winding, a rectifier connected to said secondary winding, a filter connected to the output of said rectifier to provide said anode potential and an impedance interposed between said rectifier and said secondary winding, the alternating voltage developed across said impedance varying in accordance with said load, a second voltage supply furnishing constant grid bias potential to said amplifier, means to rectify and filter the voltage across said impedance to produce a control voltage, and means to combine said control voltage with said constant grid bias potential to produce a resultant grid bias varying inversely as the load.
  • a system for supplying anode and grid bias voltages to an electronic amplifier of the class B or C type comprising a first voltage supply furnishing anode potential to said amplifier, said amplifier acting as a load on said first supply, said first supply including a first transformer having a primary winding for connection to an alternating voltage source and a pair of secondary windings, a full wave rectifier tube having a pair of anodes connected respectively to one end of each of said secondary windings and a cathode, a second transformer having a center-tapped primary winding connected between the other ends of the secondary windings of said first transformer and a secondary winding and a filter connected between said cathode and the center-tap of the primary winding of the said second transformer to provide said anode potential, the voltage developed across the secondary winding of said second transformer varying in accordance with said load, a second voltage supply furnishing constant grid bias potential to said amplifier, means to rectify and filter the voltage in the secondary of said second transformer to produce a, control voltage, and means to
  • a system for supplying anode and grid bias voltages to an electronic amplifier of the class B or C type comprising a first voltage supply furnishing anode potential to said amplifier, said amplifier acting as a load on said first supply, said first supply including a first transformer having a primary winding for connection to an alternating voltage source and a pair of secondary windings, a full wave rectifier tube having a pair of anodes connected respectively to one end of each of said secondary windings and a cathode, a second transformer having a center-tapped primary winding connected between the other ends of the secondary windings of said first transformer and a secondary winding and a filter connected between said cathode and the center-tap of the primary winding of said second transformer to provide said anode potential, the voltage developed across the secondary winding of said second transformer varying in accordance with said load, and a second voltage supply furnishing grid bias potential to said amplifier varying inversely as the load, said second supply including a third transformer having a primary winding connected in parallel with the
  • An arrangement as set forth in claim 4 further including phase shifting means interposed between each anode of said second tube and the secondary windings of said third transformer.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • General Physics & Mathematics (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Automation & Control Theory (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Amplifiers (AREA)
US668424A 1941-07-04 1946-05-09 Anode and grid bias voltage system for class b or c amplifiers Expired - Lifetime US2527406A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
NL606004X 1941-07-04

Publications (1)

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US2527406A true US2527406A (en) 1950-10-24

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US668424A Expired - Lifetime US2527406A (en) 1941-07-04 1946-05-09 Anode and grid bias voltage system for class b or c amplifiers

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US (1) US2527406A (enrdf_load_stackoverflow)
DE (1) DE860081C (enrdf_load_stackoverflow)
FR (1) FR883747A (enrdf_load_stackoverflow)
GB (1) GB606004A (enrdf_load_stackoverflow)
NL (1) NL59009C (enrdf_load_stackoverflow)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2772329A (en) * 1951-02-23 1956-11-27 Bendix Aviat Corp Correction of distortion in push-pull amplifiers
US2896096A (en) * 1953-03-17 1959-07-21 Schwarzer Fritz Power supply
US3064202A (en) * 1959-01-27 1962-11-13 Gen Electric Low current drain transistor amplifier
US3274508A (en) * 1963-10-14 1966-09-20 Webster Electric Co Inc Power amplifier including biasing means for reducing standby power dissipation

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1904272A (en) * 1928-03-07 1933-04-18 Bell Telephone Labor Inc Vacuum tube amplifier circuit
US1985946A (en) * 1929-01-25 1935-01-01 Rca Corp Amplifying and reproducing system
US2102779A (en) * 1934-02-28 1937-12-21 Rca Corp Thermionic amplifier
US2132830A (en) * 1934-11-20 1938-10-11 Dictaphone Corp Audio frequency amplifier
US2154200A (en) * 1934-11-12 1939-04-11 Rca Corp Voltage regulator device

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1904272A (en) * 1928-03-07 1933-04-18 Bell Telephone Labor Inc Vacuum tube amplifier circuit
US1985946A (en) * 1929-01-25 1935-01-01 Rca Corp Amplifying and reproducing system
US2102779A (en) * 1934-02-28 1937-12-21 Rca Corp Thermionic amplifier
US2154200A (en) * 1934-11-12 1939-04-11 Rca Corp Voltage regulator device
US2132830A (en) * 1934-11-20 1938-10-11 Dictaphone Corp Audio frequency amplifier

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2772329A (en) * 1951-02-23 1956-11-27 Bendix Aviat Corp Correction of distortion in push-pull amplifiers
US2896096A (en) * 1953-03-17 1959-07-21 Schwarzer Fritz Power supply
US3064202A (en) * 1959-01-27 1962-11-13 Gen Electric Low current drain transistor amplifier
US3274508A (en) * 1963-10-14 1966-09-20 Webster Electric Co Inc Power amplifier including biasing means for reducing standby power dissipation

Also Published As

Publication number Publication date
FR883747A (fr) 1943-07-13
DE860081C (de) 1952-12-18
GB606004A (en) 1948-08-04
NL59009C (enrdf_load_stackoverflow)

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