US2232850A - Electron discharge tube circuits - Google Patents

Electron discharge tube circuits Download PDF

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Publication number
US2232850A
US2232850A US249242A US24924239A US2232850A US 2232850 A US2232850 A US 2232850A US 249242 A US249242 A US 249242A US 24924239 A US24924239 A US 24924239A US 2232850 A US2232850 A US 2232850A
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United States
Prior art keywords
circuit
grid
feedback
control grid
cathode
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Expired - Lifetime
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US249242A
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English (en)
Inventor
Haantjes Johan
Tellegen Bernardus Do Hubertus
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RCA Corp
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RCA Corp
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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03G—CONTROL OF AMPLIFICATION
    • H03G3/00—Gain control in amplifiers or frequency changers
    • H03G3/20—Automatic control
    • H03G3/22—Automatic control in amplifiers having discharge tubes
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
    • F24F6/00—Air-humidification, e.g. cooling by humidification
    • F24F6/02—Air-humidification, e.g. cooling by humidification by evaporation of water in the air
    • F24F6/06—Air-humidification, e.g. cooling by humidification by evaporation of water in the air using moving unheated wet elements
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03D—DEMODULATION OR TRANSFERENCE OF MODULATION FROM ONE CARRIER TO ANOTHER
    • H03D7/00—Transference of modulation from one carrier to another, e.g. frequency-changing
    • H03D7/06—Transference of modulation from one carrier to another, e.g. frequency-changing by means of discharge tubes having more than two electrodes
    • H03D7/10—Transference of modulation from one carrier to another, e.g. frequency-changing by means of discharge tubes having more than two electrodes the signals to be mixed being applied between different pairs of electrodes
    • 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
    • H03F3/02—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements with tubes only

Definitions

  • This invention relates to a circuit arrangement for the amplification and/or frequency-changing of electric oscillations whose gain can be controlled by variation of the mutual conductance of at least one of the tubes and in which use is made of negative feedback.
  • the feedback voltage or current is for this purpose derived from the circuit or circuits of one or more current carrying electodes of at least one of the if in a circuit in which the gain is controlled contolled tubes whose alternating current increases or at least remains constant if the gain is decreased.
  • the feedback voltage or current is preferably derived from the circult of a current carrying electrode, arranged between the anode and the input contol grid of a multigrid valve and the gain control is obtained by variation of the bias of a gain control grid I arranged between the said current carrying electrode and the anode.
  • a gain control grid I arranged between the said current carrying electrode and the anode.
  • the feedback is brought about by including in the circuit of the said current carrying electrode or electrodes a feedback impedance which is also included in the input circuit of the valve and the anode circuit for the frequency of the oscillations to be amplified and/ or to be changed in frequency is connected to that end of the feedback impedance which is connected to the cathode.
  • the gain 25 control grid and the anode have preferably arranged between them a control grid to which the locally generated oscillations are fed, a screen grid being arranged on either side of this latter control grid, the circuits of the said control grid and the said screening grids for the frequency of the oscillations to be transformed are connected to that end of the feedback impedance which is connected to the cathode.
  • the circuit of the said current carrying electrode or electrodes includes an inductance coll which is shunted by an ohmic resistance whose value is low compared with the impedance of the inductance and which is coupled inductively to a second inductance which is included in the input circuit of the valve in series with a tuned oscillatory circuit.
  • a circuit arrangement in which the intensity of the feedback is independent of the gain can be obtained by including in the input circuit of the tube a feedback impedance which has passing through it the alternating current of all current carrying electrodes; the gain control being effected by variation of the bias of a gain control grid which is arranged on the side of the input control grid remote from the cathode and which is separated therefrom by one or more screening grids.
  • Fig. 1 shows a high frequency stage which embodies the present invention
  • Fig. 2 shows a modification of the circuit shown in Fig. 1
  • Fig. 3 shows a frequency-changing or mixing circuit for use in a superheterodyne type of receiver according to the invention
  • Fig. 4 shows a further modification of the circuit of Fig. 1.
  • Fig. 1 shows the first stage of a radio receiver in which use is made of a multigrid valve I comprising in succession a cathode 2, an input control grid 3, a current carrying electrode 4, a gain control grid 5, a screening grid 6, a suppressor grid I, which is connected to the cathode, and an anode 8.
  • the antenna 9 is connected to earth through an inductance I0 which is coupled inductively to a second inductance II, the latter forming part of an oscillatory circuit which, by means of a variable condenser I2 can be tuned to the frequency of the received oscillations.
  • the oscillatory circuit II, I2 is connected to the input control grid 3 of the valve I.
  • the anode circuit of the valve I includes an inductance I3 coupled to a tuned output circuit I4.
  • the amplified high-frequency oscillations are obtained from the terminals I5 and I6.
  • the anode circuit and the circuit of the screening grid 6 are connected, so far as high frequencies are concerned, to the cathode 2 of the valve I by means of a condenser H.
  • the circuit of the current carrying electrode 4 includes a condenser I9 and a feedback impedance I8, the latter being also included in the input circuit of the valve I.
  • the feedback impedance I8 is shown in the figure as a high-frequency non-shunted ohmic resistance.
  • the gain control grid 5 has supplied to it via a conductor 20 a variable bias for gain control, said bias being varied by hand or automatically in accordance with the amplitude of the received signals. So far as high frequencies are concerned the gain control grid is connected to the cathode via a condenser 2
  • the operation of the circuit arrangement described is as follows.
  • the gain control grid 5 is placed at earth potential or at a negative potential so that part of the electrons emitted by the cathode will change their directions in the proximity of this grid and will flow to the positive electrode 4.
  • the intensity of the feedback therefore increases if the gain is reduced so that in the event of powerful signals, in which case the gain is generally to be limited to a minimum value and there is moreover a great risk of difiiculties occurring due to the curvature of the characteristic curve, the maximum negative feedback occurs, whereas in the event of feeble signals the feedback is low and the sensitiveness of the receiver is consequently not unnecessarily limited.
  • An important advantage of the circuit arrangement described resides in that the desired gain control is assisted by the variation of the intensity of the feedback so that a highly efiicient gain control is obtained.
  • the feedback impedance I8 is formed as an ohmic resistance, the latter may also serve fundamentally for generating the required negative bias for the input control grid 3.
  • the feedback impedance should, however, generally be formed by an ohmic resistance of the order of magnitude of about 2000 to 4000 ohms, said value being too high for generating a suitable bias for the input control grid.
  • the grids 4 and 6, arranged on either side of the regulating grid 5, are electrically connected within the tube.
  • Such tubes may also be used in the circuit arrangement according to the invention since generally the alternating current of the grid 4, which increases with increasing negative bias of the gain control grid, substantially exceeds the alternating current of the grid 6, which decreases at the same time. The use of such tubes may even be advantageous if the feedback set up in the event of feeble signals is desired not to be limited excessively.
  • a tube of this kind is used in the circuit arrangement of Fig. 2.
  • an inductive feedback by means of coils 25 and 26 is substituted for the feedback impedance I8.
  • the common circuit of the grids 4 and 6 includes the coil 25 which is connected to earth via a condenser 21.
  • the coil 25 is connected in parallel with an ohmic resistance 28 whose value is small compared with the highfrequency impedance of the coil 25 so that the voltage set up across this coil is substantially in phase with the alternating current of the grids 4 and 6.
  • the coil 25 is coupled inductively to the coil 26 which is included in the input circuit of the valve I in series with the oscillatory circuit II, I2.
  • the circuit arrangement generally in use with positive feedback and in which the feedback coil is coupled to the inductance of the input oscillatory circuit is preferably not used in the present instance since the use of this circuit arrangement for negative feedback would lead to considerable damping of the input oscillatory circuit and to a falling-off in selectivity.
  • this circuit would exhibit the additional drawbacks that complete linearising of the valve characteristic curve would not be obtained since for this purpose the harmonics set up by the curvature of the characteristic curve would have to occur also in the feedback voltage and due to the induction of the feedback voltage in the input oscillatory circuit the har- .monics would be weakened with respect to the fundamental frequency-
  • the circuit arrangement of Fig. 2 it is possible to obtain the desired negative bias of the input control grid in the usual manner by means of a resistance 29 included in the cathode conductor and short-circuited so far as high frequencies are concerned, by means of a condenser 29.
  • Fig. 3 shows a frequency-changing circuit arrangement embodying the invention which comprises a mixing valve 30 having a cathode 3
  • the received oscillations are fed to the input control grid 32.
  • the anode circuit includes an intermediate-frequency circuit 40 which is coupled inductively to a second intermediate-frequency circuit 4
  • the oscillations whose frequency is changed are taken from the terminals [5 and It.
  • a negative feedback is obtained by means of a feedback impedance I8 which is included in the input circuit and has the alternating current of the electrode 33 passing in it, for which purpose this electrode is connected, so far as high frequencies are concerned, via a condenser l9 to that end of the feedback impedance which is remote from the cathode.
  • the resistance I8 is connected in parallel with the series combination of a high-frequency choke 46 and a resistance 41 so that the total D. C. resistance in the cathode conductor is less than the resistance of the feedback impedance l8, the latter being generally too heavy to ensure a suitable bias for the control grid 32.
  • the anode circuit and the circuits of the screening grids 35 and 3! are connected, so far as high frequencies are concerned, to that end of the feedback impedance 18 which is connected to the cathode so that the feedback is only governed by the alternating current of the electrode 33.
  • the gain control is obtained by feeding a variable bias to the gain control grid 34. If the gain control grid is rendered more negative, the alternating current of the anode 39 decreases, whereas the alternating current of the electrode 33 increases. The intensity of the negative feedback consequently decreases with increasing gain.
  • the local oscillations are preferably fed to the oscillator control grid 33 in such manner that the feedback voltage set up across the impedance l8 does not occur in the circuit of the oscillator control grid.
  • the local oscillations set up by a separate oscillator valve 42 are transmitted inductively to a coil 43 connected between the oscillator control grid 36 and the cathode 3!, the desired negative bias of the oscillator control grid being obtained by means of a grid condenser 45 and a leak 44.
  • the inductive coupling between the oscillatory circuit 42' of the oscillator 4,2 and the circuit .of the control grid 36 upon which the local oscillations are impressed offers the particular advantage that the tuning condenser of the oscillator can be connected to earth, which in the event of a different manner of coupling, would lead to a short-circuit of the feedback impedance l3.
  • the oscillator control grid 35 lies on that side of the gain control grid 34 which is remote from the cathode, and in addition is separated from the gain control grid by a screening grid 35, the oscillator control grid exercises practically no controlling action on the electrons that change their directions in the proximity of the gain control grid so that the alternating current of the electrode 33 contains almost uniquely the frequencies of the received oscillations and does'not contain the frequency of the local oscillations.
  • the feedback current or voltage derived from the circuit of the electrode 4 (Fig. 1) or 33 (Fig. 3) respectively has practically the same time variations as the cathode alternating current.
  • the control voltage there must therefore be between the instantaneous values of the cathode alternating current and the alternating current of the electrode 4 or 33 respectively, preferably a practically constant ratio, or v,
  • the ratio in which the stream of electrons which passes through the apertures of the input control grid 3 or 32 respectively is divided by means of the regulating grid 5 or 34 respectively between the electrode 4 or 33 respectively and the other conducting electrode of the valve l or 33 respectively must be practically independent of the intensity of the said stream of electrons and hence of the voltage of the input control grid 3 or 32 respectively.
  • This condition can be satisfied by a special valve construction and/or by a special choice of the biases of the various electrodes, for example by taking care that only a very low space charge can be formed in the proximity of the control grid 5 of 34 respectively.
  • a further method of rendering the current distribution, brought about by the gain control grid 5 or 34 respectively, practically independent of the voltage of the input control grid 3 or 32 respectively consists in feeding a suitably chosen part of the input alternating voltage to the gain control grid, which may be effected in a simple manner by connecting the gain control grid so far as high frequencies are concerned, to a suitably chosen point of the input oscillatory circuit II, l2 instead of connecting it to the oathode via the condenser 2
  • the effect of the above measure may be due to the fact that part of the input alternating voltage which is supplied to the gain control grid neutralises the action of this space charge. It is found that this compensation can be obtained for all values of the gain control voltage by feeding the same part of the input alternating voltage to the gain control grid.
  • the action aimed at in this case is independent of the value of the gain control voltage.
  • the current distribution brought about by the oscillator control grid 36 is independent as far as possible of both the voltage of the input control grid 32 and the voltage of the gain control grid 34.
  • FIG. 4 A circuit arrangement which permits of obtaining a negative feedback substantially independent of the gain is shown in Fig. 4.
  • This circuit arrangement is substantially identical with that of Fig. 1 but is differentiated therefrom by the fact that the anode circuit instead of being connected, so far as high frequencies are concerned, to the cathode is connected via the condenser [9 to that end of the feedback impedance [8 which is remote from the cathode so that the feedback impedance has passing through it the alternating current of all conducting elec trodes of the tube I. Since variation of the bias of the gain control grid 5 primarily results only in an alteration of the current distribution between the electrodes 4, 6 and 8 but not in an alteration of the emission stream, the total current of all conducting electrodes is substantially independent of the gain control voltage. The feedback voltage set up across the impedance [8 will consequently also be practically independent of the gain.
  • a particular advantage of the circuit arrangement of Fig, 4 resides in that it can be arranged in a most simple manner for changing the frequency of the received oscillations. For this purpose it is only necessary to connect between the gain control grid 5 and the point of connection of the condenser 2
  • a frequency-changing arrangement with negative feedback is obtained which is substantially simpler than the circuit arrangement shown in Fig. 3 but which has the disadvantage compared with the latter circuit that the gain control is less efficient and the sensitiveness' to feeble signals is also less.
  • the invention can also be used at one or more following stages.
  • the invention is also applicable to low-frequency amplifier circuits whose gain is controlled by variation of the mutual conductance of the amplifier valves.
  • a circuit comprising an electron discharge tube provided with a cathode, an anode and a plurality of grid electrodes interposed between the cathode and anode, a signal input circuit connected to one of the grid electrodes, an output circuit connected to the anode, means for impressing a feedback voltage on the input circuit in phase opposition to the signal voltage, and
  • a circuit comprising an electron discharge tube provided with a cathode, an anode and a plurality of grid electrodes interposed between the cathode and anode, a signal input circuit connected to one of the grid electrodes, an output circuit connected to the anode, means for impressing a feedback voltage on the input circuit in phase. opposition to the signal voltage, said feedback means comprising an impedance con nected to the cathode and included in a path common to the input circuit and the circuit of one of the grid electrodes, and means for applying a gain control voltage to one of the grid electrodes other than the signal grid.
  • a circuit comprising an electron discharge tube provided with a cathode, an anode and a plurality of grid electrodes interposed between the cathode and anode, a signal input circuit connected to one of the grid electrodes, an output circuit connected to the anode, means for impressing a feedback voltage on the input circuit in phase opposition to the signal voltage, said feedback means comprising an unbypassed resistance connected to the cathode and included in a path common to the input circuit and the circuit of one of the grid electrodes, and means for applying a gain control voltage to one of the grid electrodes other than the signal grid.
  • a circuit comprising an electron discharge tube provided with a cathode, an anode and first, second and third grid electrodes interposed between the cathode and anode, a signal input circuit connected to the first grid electrode, means for impressing a feedback voltage on the input circuit in phase opposition to the signal voltage, said feedback means comprising an impedance connected to the cathode and included in a path common to the input circuit and the circuit of the second grid electrode, means for applying a gain control voltage to the third grid electrode, the intensity of the negative feedback varying directly with changes in the numerical value of the gain control voltage, and an output circuit connected to the anode.
  • a frequency changing circuit comprising an electron discharge tube provided with at least a cathode, an anode, first, second, third and fourth grid electrodes interposed between cathode and anode, a signal input circuit connected to the first grid, means included in the circuit of the second grid for impressing a feedback voltage on the input circuit in phase opposition to the signal voltage, means for applying a gain control voltage to the third grid electrode, means for impressing local oscillations on the fourth grid electrode, and means included in the anode circuit for deriving an intermediate frequency resulting from the interaction between the signal oscillations and the local oscillations.
  • a frequency changing circuit comprising an electron discharge tube provided with a cathode, an anode and a plurality of grids interposed between said cathode and anode, said grids comprising a signal control grid, a current carrying grid, a gain control grid and a local oscillator grid disposed in the order named, a signal input circuit connected to the signal control grid, means included in the circuit of the current carrying grid for impressing a feedback voltage on the input circuit in phase opposition to the signal voltage, said feedback meanscomprising an impedance connected to the cathode and included in a path common to the input circuit and the circuit of the current carrying grid, means for applying a gain control voltage to the gain control grid, means for impressing local oscillations on the oscillator grid, and means included in the anode circuit for deriving an intermediate frequency resulting from the interaction between the signal oscillations and the local oscillations.
  • a circuit according to claim 10 wherein the feedback impedance is constituted by an unbypassed resistance.
  • a circuit according to claim 10 wherein the feedback impedance is constituted by a resistance, and a series connected resistance and choke coil are connected in shunt to the feedback resistance for reducing the total direct current resistance in the cathode circuit to a suitable value for providing negative bias for the signal control grid.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Details Of Television Scanning (AREA)
  • Amplifiers (AREA)
  • Input Circuits Of Receivers And Coupling Of Receivers And Audio Equipment (AREA)
US249242A 1939-07-01 1939-01-04 Electron discharge tube circuits Expired - Lifetime US2232850A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
NL217992X 1939-07-01

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US2232850A true US2232850A (en) 1941-02-25

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US (1) US2232850A (et)
BE (1) BE434444A (et)
CH (2) CH212944A (et)
FR (1) FR856581A (et)
GB (1) GB528893A (et)
NL (1) NL64722C (et)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2488357A (en) * 1947-05-20 1949-11-15 Mcclatchy Broadeasting Company Negative feedback amplifying circuit
US2721909A (en) * 1952-01-24 1955-10-25 Marconi Wireless Telegraph Co Gain control circuit arrangements

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2488357A (en) * 1947-05-20 1949-11-15 Mcclatchy Broadeasting Company Negative feedback amplifying circuit
US2721909A (en) * 1952-01-24 1955-10-25 Marconi Wireless Telegraph Co Gain control circuit arrangements

Also Published As

Publication number Publication date
NL64722C (et)
BE434444A (et)
FR856581A (fr) 1940-06-18
CH217992A (de) 1941-11-15
CH212944A (de) 1940-12-31
GB528893A (en) 1940-11-08

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