US2118122A - Amplifying system - Google Patents

Amplifying system Download PDF

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Publication number
US2118122A
US2118122A US698486A US69848633A US2118122A US 2118122 A US2118122 A US 2118122A US 698486 A US698486 A US 698486A US 69848633 A US69848633 A US 69848633A US 2118122 A US2118122 A US 2118122A
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US
United States
Prior art keywords
cathode
grid
circuit
anode
capacity
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Expired - Lifetime
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US698486A
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English (en)
Inventor
Pol Balthasar Van Der
Posthumus Klaas
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RCA Corp
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RCA Corp
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Publication date
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Publication of US2118122A publication Critical patent/US2118122A/en
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    • 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
    • H03F1/08—Modifications of amplifiers to reduce detrimental influences of internal impedances of amplifying elements
    • 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
    • H03F1/08—Modifications of amplifiers to reduce detrimental influences of internal impedances of amplifying elements
    • H03F1/10—Modifications of amplifiers to reduce detrimental influences of internal impedances of amplifying elements by use of amplifying elements with multiple electrode connections

Definitions

  • This invention relates to amplification circuit arrangements comprising thermionic amplifying valves having one or more grids, and particularly to the manner in which the various circuits associated with the amplifying valve such, for example, as the control grid and anode circuits of a triode or the control grid and screen grid circuits of a screen grid valve are connected to the cathode of the amplifying valve.
  • This conductivity obviously has the same effect as a resistance in parallel with the input oscillatory circuit and would cause a damping thereof.
  • a grid-cathode capacity which is also dependent upon the negative grid voltage and which is to be imputed essentially to variable space charge phenomena, occurs between the control grid and the cathode.
  • the invention has for its object partly or wholly to neutralize or to balance the said phencmena, via, the decrease in control grid-cathode resistance and the control grid-cathode capacity that is dependent upon the negative bias.
  • this object is obtained by so proportioning the impedance of the part of the anode-cathode connection in the case of a triode or the part of the screen grid-cathode connection in the case of a tetrode which is in common to the control grid-cathode connection that the conductivity between the control grid and the cathode and/or the control grid-cathode capacity that is dependent upon space charge phenomena are neutralized partly or wholly whereby the detuning of the resonant input circuit by these factors is substantially eliminated.
  • Fig. 1 illustrates diagrammatically a triode and the various impedances associated with its ele ments when it is connected in a circuit
  • Fig. 2 is a diagram of the impedances illustrated in Fig. 1
  • Figs. 3 and 4 show circuit diagrams for connecting a triode in accordance with the invention.
  • Fig. 5 is a circuit diagram of another modification of the invention and Fig. 6 shows a circuit diagram of a screen grid amplifier embodying the 1 invention.
  • Fig. 1 shows by Way of example, an indirectly heated triode comprising an electrically heated filament F, a cathode K, a grid G and an anode A. These electrodes are connected by means of connecting wires to contact pins I, 2, 3, 4 and 5 I fixed in the base.
  • the said connecting leads include impedances designated by 29. and Zr.
  • the internal tube capacity Cat, Cgf and Cag are indicated in this figure.
  • the impedance Zr which may be the selfinductance of the lead in wire to the cathode is also in the anode circuit and the anode current being in phase with the grid voltage, causes a voltage drop over the self-inductance of the cathode .lead which lags behind the applied input grid voltage by an angle of substantially degrees.
  • the series circuit of the cathode-grid capacity and the self-inductance of the cathode lead As the cathode-grid capacity is relatively small, this series circuit has a substantially capacitive character.
  • the apparent resistance'between the grid and the cathode should be rendered a maximum which according to the invention is ensured by minimizing the inductance L: which, as is shown in Fig. 2 when the impedance Zr is replaced therein by aninductance Lf, couples the anode circuit to the grid circuit, in which case, as is immediately apparent from the above equation, the resistance R becomes very large or may even assume a negative value so that a tuned circuit connected between the grid and the cathode is but little damped or even negatively damped. 7
  • the inductance can be made very low byvconnecting the anode circuit and the grid circuit each separately to the oathode and by so arranging the connecting wires necessary for this purpose that the coupling between both is small.
  • the arrangement of such an amplifying valve with two connectingwires from the base to the indirectly heated cathode is diagrammatically shown in Fig. 3.
  • This figure shows an indirectly heated triode comprising 7 an anode A, a grid G and an indirectly heated cathode K. For the sake of clearness the heater is omitted.
  • Two wires I and 2 are fixed to a point P of the cathode and are connected to separate pins in the base as diagrammatically shown.
  • the two connecting wires are spaced as far apart as possible in order to minimize the magneticcoupling between them.
  • the grid circuit is connected to one of the connecting wires, say I, and the anode circuit to the other connecting wire 2.
  • the inductance designated by Li becomes very small and consequently the apparent conductivity also becomes very small or even negative.
  • the two connecting wires l and 2 should be connected to the same point of the cathode but as an alternative they may be connected to different points of the cathode.
  • the method represented in Figure 3 has a limitation in the fact that in connection with the second connecting wire to the cathode the base has to be provided with a supplementary connection or pin.
  • This disadvantage can be obviated by using one of the current leads for the filament that heats the cathode K, partly as a connecting wire to the cathode.
  • This circuit arrangement is illustrated in Figure 4 in which the indirectly heated cathode K is taken out of the envelope of the valve not only by a conductor l but also by way of a conductor 2 provided between a point of the cathode and the heater and of one of the cathode supply leads 3 and 4.
  • the heater is supplied with alternating current it is desirable that the grid circuit should be connected to the conductor I, the anode circuit to one of the cathode supply leads 3 and 4 in order that the disturbances by the fluctuating voltage of the filament may be avoided as far as possible.
  • the coupling introduces an apparent grid-cathode impedance which can be represented in part by a negative capacity, that is to say, by an impedance with the same frequency dependency as a capacity but with opposite phase.
  • a coupling of the anode and the grid circuit permits of partly or wholly neutralizing the increase of the grid-cathode capacity with decreasing negative grid voltage which is due to space charge effects, since this capacity and the negative capacity brought about by the coupling due to the resistance R: are dependent in the same sense upon the slope S.
  • Such a coupling by means of an ohmic resistance included in' the connecting conductor to the cathode, is particularly useful when a plurality of amplifying stages are interconnected by oscillatory circuits, the tuning of the circuits being effected by means of condensers which are mechanically coupled to each other. If in such an amplifier the gridbiases of the amplifying valves are varied differently, for example for volume control, the circuits will thus be caused to be out of tune relatively to each other.
  • the impedance Za inthe anode circuit behaves, insofar as high frequency currents are contemplated, essentially in a capacitative manner.
  • Za can be represented by and for the admitance between the terminals 3 and 4 in Figure 1 is found from which it is apparent that the latter term viz.,
  • Fig. 6 shows such an embodiment of the invention as applied to a tetrode having a screen grid SG having an impedance ZSG in the screen circuit and which corresponds to the impedance Za of Fig. l.
  • the usual useful load circuit impedance ZL is connected to the anode and the cathode and heater connections I 3 and 4 are similar to those shown in Fig. 4.
  • an electron discharge tube having a cathode, a heater for said cathode, a control grid, a screen grid and an anode, a connection within said tube between said heater and one end of said cathode, a circuit including an impedance connecting said screen grid and said heater, an input circuit connecting said control grid and being directly connected to the other end of said cathode and an output circuit connected to said anode and directly to said one end of said cathode.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Amplifiers (AREA)
  • Details Of Valves (AREA)
  • Channel Selection Circuits, Automatic Tuning Circuits (AREA)
US698486A 1933-01-26 1933-11-17 Amplifying system Expired - Lifetime US2118122A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
NL414051X 1933-01-26

Publications (1)

Publication Number Publication Date
US2118122A true US2118122A (en) 1938-05-24

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ID=19786001

Family Applications (1)

Application Number Title Priority Date Filing Date
US698486A Expired - Lifetime US2118122A (en) 1933-01-26 1933-11-17 Amplifying system

Country Status (6)

Country Link
US (1) US2118122A (enrdf_load_stackoverflow)
BE (1) BE400867A (enrdf_load_stackoverflow)
DE (2) DE676285C (enrdf_load_stackoverflow)
FR (1) FR767185A (enrdf_load_stackoverflow)
GB (2) GB414051A (enrdf_load_stackoverflow)
NL (1) NL40365C (enrdf_load_stackoverflow)

Also Published As

Publication number Publication date
DE656699C (de) 1938-02-12
DE676285C (de) 1939-06-01
GB414051A (en) 1934-07-24
GB415009A (en) 1934-08-16
NL40365C (enrdf_load_stackoverflow)
BE400867A (enrdf_load_stackoverflow)
FR767185A (fr) 1934-07-12

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