US2213398A - Vacuum tube circuit - Google Patents

Description

p 1940- R. J. KIRCHER 2,213,398-

, VACUUM TUBE CIRCUIT Filed July 22, 1938 2 Sheets-Sheet 1 IIQVVENTOII? a J. K/RCHER ATTORALEV Sept. 3, 1940.

VACUUM TUBE CIRCUIT Filed July 22, 1938 2 Sheets-Sheet 2 INVENTOR y RJ K/RCHER ATTOkA/EK R. J. KIRCHER {2,213,398 v Patented Sept. 3;, 1940 UNITED STATES PATENT OFFICE 2.213.398 VACUUM TUBE omoorr Raymond J. Kircher, Neptune; N. J., assignor to Bell Telephone Laboratories, incorporated, New

York, N. Y., a corporation of New York Application July 22,1938, Serial No. 220,618

16 Claims. (01. 1'z9--1'r1.5)

This invention relates to vacuum tube circuits and more particularly'to'such circuits in which the interelectrode capacity between control grid and anode is or may be neutralized.

There is a need for a. simple, inexpensive circuit arrangement capable of use either for receiving or transmitting purposes.

condition is that the means used for one or the other purpose be usable for the other with some simple change or readily operated control. An object of this invention is to meet this need.

A feature of the invention comprises using an electron discharge device having inherent capac ity between its control electrode and its anode,

associating circuit means with such'electrodes so that the intrelectrode capacity. is neutralized thereby preventing the occurrence of a condition of self-oscillation, and providing other means to alter the constants of the neutralizing circuit whereby the device functions as an oscillator.

A further feature of the invention comprises connecting circuit means between a pair of electrodes Of anelectron'discharge 'device and providing relay means to change the characteristics of the circuit meansto a desired extent, such relay means, for example, being manually or audio-frequency-operated or cont olled. Another feature of. theinve ion comprises connecting circuit means between a pair of elec- 3' trodes of. anelectrondischargedevice, said circuit means including .a capacity element provided by a second electron discharge device. A more complete-understanding of this inven- 'tion and its various features will be obtained from the detailed description which follows hereinafter, taken in conjunction with the appended drawings, wherein: I

I Figs. 1 and 2 show vacuum tube circuits embodying the invention, f, Fig. 3 shows a vacuum tube transmitter circuit I embodying theinvention;

FigM shows a'combined transmitter and re-' ceiver circuit embodying. the invention; and

Flgs..5 and 6 show electron c means for keying.

4 the neutralizing circuit of a vacuum tube,

The circuit of Fig. 1 comprises an electron p discharge device or triode [0 having a cathode -I I, a control grid l2, and an anode l3. A tuned circuit I4 is connected to the grid-cathode and a second tuned circuit l5 is'connected across the cathode-anode. A source of grid biasing potential and a source of plate potential are indicated. \The cathode may be',.as shown, of the indirectly heated type. The numeral It indicates the in- 55 herent capacity between the grid-and anodethat A preferable;

per cent of that at which neutralization oc- ---of the circuit 28. may be accomplished by the "tromagnet or relay 22 and battery 23 by closure of the contacts of key 24, armature 25 engaging causing condenser 2| to be removed from the "26 being in engagement.

neutralizing circuit, whereby the tube ceases to signal input terminals 40, is transformer coupled B, and to the neutralizing circuit control circuit may cause undesired oscillation of the device l0,

particularly when it is being used, for example, as adetector, an amplifier, ora demodulator. Various arrangements have been proposed to 5 neutralize this capacity, and when high frequencies, for example, of the order of hundreds of kilocycles or of megacycles, are involved, neutralizing by connecting an inductance between the control grid and anode has been found par- 10 ticularly efiective. In Fig. 1, the neutralizing circuit 28 is shown as comprising inductances l1, l8, a variable condenser I9, and a blocking condenser 20'. When the circuits l4, l5 and 28 are tuned to the same frequency the vacuum 15 tube, as is known, will not oscillate.

If either the reactive or capacitive constants of the anti -resonant circuit between the grid and anode are altered, and allthe other circuits remain unchanged, a condition of oscillation oc- 2o curs at a frequency that may be within a few curred. This alteration in the L or C constants connection of condenser 2| in shunt with con-. 25 denser IS on completion of a circuit for the elecvirithcontact 26 so long as the key is operated. v The vacuum tube will oscillate until the contacts of key 24 are opened, releasing armature 25 and circuit betweenthe grid and plate of the tube. Instead otthe tube normally being neutralized, it may'normally be used as an oscillator with a '35 portionof the neutralization circuit shunted out as shown in Fig. 2, the armature 25 and contact When it is desired to place the tube in condition for use, for example, as a detector. or asan amplifier, operation of the key to close a circuit for. the electromagnet causes separation of the armature and associated contact to place the inductance l1 effectively in the function'as an oscillator.

-' In Fig. 3, the invention is embodied in a signal wave transmission circuit. An audio frequency amplifier A, having suitable speech or other audio to the normally'neutraliz'ed vacuum tube circuit C. The amplifier may be ofany suitable type and is shown by way of illustration as a twostage transformer-coupled amplifier embodying three electrode tubes of the indirectly heated 70 initial grid biasis provided by battery 15 to give cathode type. The neutralizingcircuit so for the tube l comprises an inductance 4|, a variable condenser 42, and blocking condenser 20. The tuned circuit l5 comprises the output circuit for the neutralized vacuum tube and is coupled to the grounded antenna 43. The control 'circuit C comprises the relay or electromagnet 44, shunted by a by-pass condenser 45, in series with a rectifier 46, for example of the copper-oxide type, and the secondary winding of amplifier output transformer 41. An armature 48, normally disengaged from its associated contact 49, is controlled by the electromagnet, and condenser 5|, upon engagement of the armature and associated contact, is adapted to be included in the neutralizing circuit to alter its constants to the end that the tube is no longer neutralized and functions as an oscillator. In operation,

audio impulses are impressed on the input of the amplifier, and are amplified. A part of the amplied output is rectified by rectifier 46 to cause the control relay to close the circuit between the armature and associated contact to alter, in pre- 4 determined manner, the constants of the neutralizing circuit whereby the tube I 0 oscillates. The plate of the tube is simultaneously modulated by the amplified audio signal output and the modulated oscillator output is impressed on the antenna and radiated therefrom. Upon cessation of the audio signal input, the electromagnet deenergi'zes, releasing the armature, and the tube I0 is returned to its non-oscillatory condition pending arrival of further amplified audio signals.

The circuit arrangement .of Fig. 4 embodies the arrangement of Fig. 3, and includes means for receiving ordetecting an incoming signal during the neutralized condition of thetube, in which I period the tube l 0 functions as a simple plate detector. The receiving means comprises a telephone headset 60 connected to thesecondary of the audio transformer 6| whose primarywinding is connected'in the cathode circuit and by-passed A for radio frequencies. The neutralizing circuit 50 differs slightly from that of Fig. 3. Condenser 5| is connected in shunt to condenser 42', the constants of the inductance 4 and the condensers being such'that the grid-to-plate capacity is normally neutralized, engagement of the armature 48 and contact 49 altering the circuit so that the vacuum tube functions as an oscillator.

The circuits of Figs. 5 and 6 show electronic means for keying the neutralizing circuit of tube In. The input capacity of the control electron discharge device or triode 12 forms a part of the neutralizing circuit of the tube l0 and is initially adjusted so that with the inductance 13 it neutralizes the inherent grid-to-plate capacity ii of tube ID. This .input capacity, as'is known, may be expressed in the form CFl+(}L|-1)cgp, where C3! is the geometrical capacity between control grid I4 and cathode l0, Cgp is the geometrical capacity between the grid and the anode II, and ,u is the effective voltage gain of the device 12. Variation of the biasing potential on the control grid 14 of tube 12 causes a variation in the input capacity thereof, thereby altering the constants of the neutralizing circuit a predetermined amount so as to cause the tube In to function as an oscillator. In the arrangement of Fig. 5, an

the initial desired input capacity. This initial bias may be changed to a desired degree by superwhich is connected in series with a source 11 of low frequency current, for example, 1000 cycles per second, and a normally open key 1.8. 01', as

shown, in Fig. 6, the initial grid bias may be furnished by battery 80, the bias being changed to a. desired degree by closure of key 18 to eflfect a predetermined change in the input capacitywhereby the neutralizing circuit no longer functions to prevent tube' [0 from oscillating. Coils 8|, 82, 83 are radio frequency chokes, condensers 84, 85 and 86 are radio frequency by-pass condensers, and condensers 81, 88 are blocking condensers.

Although this invention has been disclosed with reference to various specific embodiments, it is to be understood that it is to be considered as limited in scope by the appended claims only.

What is claimed is;

1, In combination, an electron discharge device comprising a plurality of electrodes and having such inherent capacity between a pair of said electrodes that it is capable of generating oscillations, means rendering said capacity efiective to cause said device to generate. oscillations, means for neutralizing. the eflect of the capacity between said electrodes, and audio frequency operated means for altering said-second means so that said interelectrode capacity ceases to be. neutralized and said device will generate oscillations.

l 2. In combination, an electron discharge device comprising a cathode, a control grid and ananode, said device having an inherent capacity between said control grid and anode enabling it to generate oscillations, means rendering said capacity eifective to cause said device to generate oscillations, an anti-resonant circuit connected between said grid and anode for neutralizing the efiect of the capacity between said electrodes, and relay means for altering the constants of said circuit to cause said capacity to cease to be neutralized and to enable said device to act as an oscillator.

' 3. In combination, an electron discharge device comprising a cathode, a control grid and an anode, said device having an inherent capacity between said control grid and anode enabling it anode, said device having an inherent capacity between said control grid and anode enabling it to act as an oscillator, means rendering said capacity effective to cause said device to generate oscillations, an anti-resonant circuit connected between said grid and anode for neutralizing the eifect of the capacity between said electrodes, and audio frequency controlled relay means for altering the constants of said circuit to cause said capacity to cease to be neutralized and enabling said device to act as an oscillator.

5. In combination, an electron discharge devicecomprising a cathode, a control grid and'an anode, a tuned grid-cathode circuit, a tuned cathode-anode circuit, a tuned circuit across the grid and anode of said device, said circuits being normally tuned to the same frequency whereby lay 2,21s,ees

any tendency for said device to oscillate because of interelectrode capacity is neutralized, and means for modifying the constants of the gridanode tuned circuit to cause said device to os cillate.

6. In combination, an electron discharge device comprising a cathode, a control grid and an anode, a tuned grid-cathode circuit, a tuned cathode-anode circuit, a tuned circuit across the grid and anode of said device, said circuits being normally tuned to the same frequency whereby any tendency for said device to oscillate because of interelectrode capacity is neutralized, and manually operated means for modifying the constants of ,the grid-anode tuned circuitto cause said device to oscillate.

'7. In combination,-an electron, discharge device comprising a cathode, a control-grid and an anode, a tuned grid-cathode circuit,a .tuned cathode-anode circuit, atuned circuit-across the grid and anode of said device, .said circuits being normally tuned to the same Irequency whereby any tendency for said of interelectrode capacity is neutralized, and audio frequency operated means fol-modifying the constants of the grid-arrode'tuned jcircuit to..

cause said device to oscillate;

8. In combination, an electrorf'discharge. de-

vice comprising a cathode, a control grid and an anode, a tuned grid-cathode circuit, a tuned cathode-anode circuit, a tuned circuit across the grid and anode of said device,' said circuits being normally tuned to the same frequency whereby any tendency for said device-to oscillate because of interelectrode capacity is neutralized, and regrid-anode tuned circuit to cause said device to oscillate.

9. In combination, vice comprising a plurality of electrodes, the inherent interelectrode capacity of said device being such that it maybe used' as a generator of oscillations, means renderingsaid capacity efi'ective to cause said device to generate oscillations,

circuit means includinganjnductance for neutralizing the effectof the capacity between said electrodes, and audio frequency operated means for changing said circuit means so that said capacity ceases to be neutralized andsaid device becomes a generator of oscillations.

10. In combination, an audio frequencyjamplig fier, an oscillations generating vacuum tube circuit, means for neutralizing any tendency for the vacuum tube to generate oscillations, means responsive to a portion of the amplifier output to modify the characteristics of said neutralizing means so that the vacuum tube generates oscillations, and means connectingsaid amplifier and said circuit for modulation of the oscillations in accordance with the amplifier output.

11. In combination, an electron discharge dedevice tooscilla'te because means for modifying the constants of the an electron discharge decapacity vice comprising a plurality of electrodes, means ;co nnected directly between a pair of said electrades for neutralizing the efiect of capacity between said pair of electrodes, said means includ-.

' trodes for neutralizing the efiect of capacity between said pair of electrodes, said means including an electronic device providing a capacity element in said means, and means individual to said electronic device for adjusting'the capacity of said capacity element.

13. In combination, an electron discharge device comprising a plurality of electrodes and having a tendency to oscillate because of inherent interelectrode capacity, circuitmeans for neutralizing said tendency, said means including an electron discharge device having a plurality of electrodes, theinterelectrode capacity between which provides a capacity element in said neumeans'including .a space discharge device comprising a' control grid, a cathode and an' anode,

the inputcapacity of said second device being a capacity element in said circuit means, and

means for changing the bias on the second devic'es control grid to change said input capacity a predetermined amount so that the first devices oscillation tendency is no longer neutralized.

15. In combination, an oscillations generating electron discharge device, said-device comprising tralizing means, and means for changing the a control grid, a cathode and an anode, circuit means including inductance and capacity elements connected between the grid and anode,.

means for impressing a modulating signal input on said device, and relay means for changing the constants of said circuit means to a predeter mined extent, said relay means being responsive to a portion of the input to said device.

- 16. In combination, an electron discharge-device comprisinga control grid, a cathode and an anode, circuit means'including inductance and elements connected between the grid and anode, and audio frequency operated relay means for changing the constants of said circuit means to a predetermined extent. 1

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