US1832261A - Non-singing amplifier - Google Patents

Description

Nov. 17, 1931.

G. H. STEVENSON NONSINGING AMPLIFIERA Filed NOV. 10. 1928 Patented Nov. U17, 1931 iid *usarse Artur israel esonera rr. srnvENsoN, or soUNnf BEACH. ocNNncrIcufr, 'essieNoi-t Toni-imams. n

PHONE neneruercnrns, INCORPORATED, or New Yoeri, N. Y., vAV oonronATroN or NEW YORK NON-SING-VANG MPLIFEER Appncationinea November 1o, i928. serial No. 318,354.

rlhis invention relates to high frequency vacuum tube ampliiers and more particularly to improved circuits whereby the operating elilciency of such ampliiiers is increased.

A. general ob]- ect of the invention is to prevent undesirable singing or regeneration in high frequency amplifier circuits.

T he prevention of singing due to the interelectrode capacity requires that the retro-active E. M. F. (or feed back) at all times be Zero or else inV such phase relation with respect to the input E. M. as to produce loss.

of amplilication (or degeneration). Y In accordance with the present invention this I1s accomplished by maintaining constant similarvity ot the impedances between the plateiand grid and between the filament and grid. rlhis produces a degenerative action at all frequencies and also makes the degenerative action substantially constant at all Jfrequencies.

Two simple tuned circuits are employed which by virtue of mechanical coupling of the tuning elements are always resonant at the same frequency, one circuit beingconnected between the grid and filament and the other between the grid and plate. By this means, the impedances of the two paths are maintained similar at all frequencies and a constant degenerative feed back is secured. By incorporating the plate to grid branch as part of the input circuit along with the gridfllament branch, two input E. M. Ffs are introduced, which by the proper poling yof the circuits, may be made additive with respect to the normal amplifying` action of the tube, and may be made to substantially neutralize each other with respect to the direct transmission of currents to the output circuit through the impedances ot' the tube. The input circuit may for example be coupled inductively` to both the circuit between gridV and lilament and the circuit between grid and plate. Preferably then the couplings kwill be reversed with respect to each otherl in phase and balanced in degree so that no current is directly transmitted to the space path or the output circuit. input voltages aid in producing amplification.

Both resonant circuits may be tuned by In this case the two' means of a Vvariable condenser, in which case it is desirable that their rotors be at `A() ground potential to avoid the disturbances due to hand capacities, and to simplify their mechanical connector. This may be done by supplying the lilament current through parallel inductive windings and arranging these windings so that they will comprise a part of the tuning circuit between grid and filanient; supplying the plate potential through the inductivel winding connected between the gridV and plate; and grounding the grid of the vacuum tube. A blockingcondenser is employed between theplate and output wind-- ing to prevent the plate potential'from being lmpressedonthe lil'ament ot thevacuum tube. The invention will be better understood by referring to the following description and accompanying drawings Y showing preferred formsot embodiment. e

Fig. 1 represents a radio receiving circuit comprising two stages of radio frequency amplilication, a detector, an audio amplifier and a loud speaker. v l Fig.l l-A is a modified form of that portion of Fig. 1 between lines X-X and YV-Y. Referring to Fig. 1 the amplifier tube 1 has an input circuit between grid 2 and lilament 3 which consists of a coil Ll' across which is connected a tuning capacity 5, and an input circuit between grid 2 and'plate G'which consists of a coil 7 across which is connecteda tuning capacity 8. Coil 4 has a biilar winding, one end; ot the bililar windingsbei'ng connected-to the'terminals of the lament 3 of vacuum tube 1 and the other end connected .across the filament battery 9. The antenna a locking condenser to prevent positive ECE i "B potential 13 from reaching the filament 3.

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Tuning condensers 5 and S are preferably connectedv to the same control so that both resonant circuits Ll-- and 7 8 may be tuned together. Preferably also, the rotors 17 and 18 of condensers 5 and 8 are connected to grid 2. This arrangement permits grounding the grid 2 of thermionic tube 1 as shown at 19. YThe effect of hand capacities'on condensers 3 and 5 is thereby reduced-to` a minimum. Y

Since both resonant circuits are tuned at the same ti1ne,no ysinging takes place even when the circuits are beingv tuned to the desired frequency because of the fact that the similarity of the impedances of the two circuits 4 5 and 7 8. maintains lthe grid 2 constantly at an oscillating potential midway between the plate 6 and the .filament 3. Furthermore, by maintaining` constant the similarity of the impedances between plate 6 and grid 2 and between the lgrid 2 andthe filament 3 a degenerating action takes place which is substantially constant at all Vfrequencies. rlhe amount of degeneration can be controlled byv varying the values Vof the impedances of circuits land 7 8. As the impedance of circuit 7 8 is increased over that of circuit 4 5, the amount of degeneration decreases. The impedances will be in the ratio of the inductances of the tuning coils when appropriate tuning condensers are used.

The coupling from the antenna circuit to the input circuit of vacuum tube 1 through coils 11 and 12 is reversed with respect to the input circuits and balanced so that no current flows from plate 6 and grid 2. The input voltages to coils 4 and 7 then aid in producing amplification.

The second stage of hiO'h frequency amplification comprises an amplifier tube 21 having an input circuit similar to that of amplilier tube 1 and comprising aninputpcoil 24 lconnected between `grid 22 and filament 23,

and anpinput coil 27 connected between grid 22 and plate 26. Coils 24 and 27 Vare inductively coupled. Variable condensers 25 and 28 are connected across coils 24 and 2'?, respectively, for tuning' purposes. As-indicated by the dotted lines, they are preferably tuned at the same time in a manner similar to condensers 5 and 8.

Anl additional circuit 20 30 comprising an inductance coil 20 and an impedance 30 is inductively coupled to coil 27. Coils 16 and 2O are so constructed to have similar characteristics. The value of the impedance 30 is preferablymade the same as the plate filament impedance of vacuum tube 1. This circuit 20 30 then simulates the effect of the circuit 15e-16 which is inductively coupled to circuit 24 25. Circuit 20 30 will in `general be unnecessary7 wnen coils 16 and 24.- are loosely coupled. In this case only one input, E. M. F. is present, and a certain direct transmission may talre place between the input and the output circuits of the tube. rlhe non-oscillating qualities of the circuit are however not affected.

The output circuit of Vacuum tube 21 is coupled through coil 36 to a detector circuit so that the signalingwaves p ss to the detector and from the letect r through the audio amplifier to the loud speaker. lf still greater amplification of the high frequency signals is desired an additional stage or stages similar to the two shown, can be added.

The modified interstage radio frequenc)Y coupling arrangement of Fig. com- .prises two inductances 31 and 32 connected in the output `circuit-*of thermionic tube 1 having their couplings reversed with respect to each other. Inductance 31 is inductively coupled to inductance 27 and inductancc is ind ctively coupled to inductance ylie input voltages to coils and 2'? then aid in producing amplification.

`The circuit Cif-Fig. 1 has been illu. 'lrated and described :is employing different circuit connections in the two radio frequency stag It will be understood, of course, that this is .iter purposes of illustration and that it 1s within the invention to employ either identical or different types of circuits in the different stages. For example7 to use the same type of connection for stage 2 that is used for stage 1 it is merely necesi-:ary to replace the elements included between the lines K X. and Y Y of Fig. 1 by the elements shown in Fig. 1 A.

While several embodiments of the invention have been shown and described in detail, it is understood that the invention is generic in character and is not to be construed as limited to these particular embodiments since numerous modifications thereof may be made by ersons skilled in the art without departing' from the spirit of applicants invention, the scope of which is to bc determined by the appended claims.

, That is claimed is:

1. The combination of an evacuate Vessel having a plurality of electrodes incl ding grid, a. plate and a filament, a source of esci,- lations of an ultra-audio frequency, and means coupled to said source of oscillations for maintaining` the grid constantly at an oscillating` potential intermediate betwee the plate and the filament, said means ceniprising two circuits resonant at the same frequency, one connected between grid and plate and the other between grid and filament.

2. In an electrical system comprising a thermionic device having a control electrod an anode.I and a cathode7 means for ground-- ing said control electrode. an input circuit. an output circuit including the anode and cathnseaaen controlelectrode ands'aid cathode, anntlier part of said input circuit including said control electrode andY said anode.

3...-Radio, frequency amplifying apparatus comprising a thermionic vacuum tube having a lamen't, grid and plate, two equal inductances, apair ofv simultaneous adjustable condensers of equa-l capacity connecte-d lin eec.- tive shunt to said inductances, and adapted to tune said inductances, ,to resonance with a signa-l, ineans associated with' said condensers whereby the adjust-nient. of one, accompanied by the adjustment of the other, leads from said filament to one end ofone of said inductances, a. lead froinsaid'plate. to one end of the other of said inductances, a connection from said grid tothe other ends of said inductances, said connection to one of said inductances including a capacity, and an inductance and a capacityin the output circuit of said tube. v

et. Radio. frequency amplifying apparatu comprising a tliermioni'c Vacuum tube having a filament, grid and plate, two equal inductances, one of said inductances comprising two conductors bililar wound to vpermit the filament to have one D. C. potential and a different A.. C. potential with respect to the other electrodes, a pairof simultaneous adjustable condensers of equalcapacity con-'` nected in effective shunt to said inductances and adapted to tune said inductances to resonance with a signal, inea'ns associated with said condensers whereby the adjustment of one is accompanied by the adjustment of the other, leads from said filament' to said biiiiar. wound inductance, a lead from said plate to one end of the other of said inductances, a connection from said grid to the other end of Ysaid inductance connectedfto said plate and a connection from said grid to one of the two conductors of said biiilar wound 'inductance, said connectionto said inductance connected to said plate including a capacity, and an inductance and acapacity 1 in the output circuit of said tube.V

5. Radio frequency amplifying apparatus comprising a thermionic Vacuum tube having a filament, grid and plate, an inductance, a variable capacity connected in effective shunt to said inductance and adapted to tune said inductance to resonance Ywith a signal, a lead from said plate'to one end of said inducta-nce, a connection from said grid to the other end of said inductance, said connection including a capacity, a second in@ ductance comprising two conductors bifilar and an. indructanceand` acapacity in the. output circuit ofsaid tube.V

' 6. Aradioreceiving circuitcomprising an antenna circuit, a .pluralityl of three-element radio frequency amplierl tubes having a grid, a plate and a lilament andy connected' in cascade', each of said; radio frequency anrplilier tubes having associated therewith an inductanceya variable capacityV connected in effective shunt to said inductance, and adaptj ed to tune said inductance to resonance with' a signal, a lead from said plate to one end of said inductance, a connection from said grid vtno-theother-'end of said rinductance, said connection includingy a capacity, a second 1nrducta-nce comprising two conductors bifilar wound, a rrariable capacit,7 connected in ef- :fective shuntto one of said; bililar windings,

and` adapted to tune said inductance to resonance with said signal, a connection from one end of said last. mentioned bilar windingto said arida connections' from the other ends of said bifilar windings to `said filament` and an inductance and a capacityv in the output circuita detectorl circuit coupled to the outa c ,sr-rid and plate, andthe other of said antenna inductances` coupled to said inductance con-` nected between grid and filament.

7.Radio frequency amplifying apparatus comprising a thermionic vacuuintube having a filament, arid and plate. an inductance, a variable capacity connected in effective shunt to said -inductance and adapted to tune said i mentioned bililar winding-to said grid. connections from the other ends of said bifilar windinns to said filament, an inductance and 120 a capacity in the output circuit of said tube,

an input circuit inductively coupled to said bifilar wound inductanceand a circuit comprisingan inductance and an eliectiae resistance, simulatingy the inductance and eiiective l resistance of 4said Vinput, circuit, inductively coupled to said inductance connected between said grid and' plate.`

8. Aradio receiving` circuit comprising an Y antennay circuit, ai plurality of'threeeelement 3U radio 'frequency amplifier tubes having a grid, a plate and a filament and connected in cascade, each of said radio frequency amplifier tubes having associated therewith an inductance, a variable 'capacity connected in effective shunt to said inductance, and adapted to tune rsaid inductance to resonance with a signal, a lead from said *plate to one end of said iiiductance, a connection vfrom said grid to the other end of said inductance, said connection including a capacity, a second inductance comprising two conductors bifilar wound, a variable capacity connected in effective shunt to one of said biiilar windings, and adapted to tune said indiictance to resonance with said signal, a connection from one end ofl said last mentioned bifilar winding' to said gri d, connections from the other'ends.

of said biiilar windings to said filaineiit,"and an inductance and a capacity in the output circuit, each of s'aid'radio frequency -amplivtier tubes, with the exception of the tube connected to said antenna circuit, having a circuit comprisingV an inductance and an eifective resistance which simulates the inductance and effective resistance of the output circuit of the preceding' amplifier tube inductively coupled to said induc'tance connected between said @rid and plate; a detector circuit, an audio amplifying circuit and a sound reproducing device, said antenna circuit including two inductances having their couplings reversed with respect to each other, one of said inductances'inductivelv coupled to said inductance lconnected between grid and plate, and the other of said antenna inductances coupled to said inductance connected between grid and filament.

9. Ina radio system of communication the combination with a three-electrode thermionic tube. having an input circuit and an output circuit of an input transformer having two secondarics inY said input circuit, one of said secondaries connected between the control electrode and anode of said thermionic tube and the other of said secondaries connected between said control electrode and the 'cathode of said thermionic tube. said secondary windings of said input tran sforiner operating to maintain said control electrode constantly at an oscillatina potential intermediate between said anode and cathode, an'output transformer havingl a primarv in said output circuit', and

plate of the following radio frequency ainplitler Vtube and the other inductively coupled to saidr inductance connected between the grid and filament of said last mentioned tube.

ll. The combination with an evacuated i vessel having a Vplurality of electrodes, of a` aiidion having a grid, an anode and a cathode y and having capacity between the grid and the anode and having a timed input circuit be tween said grid and said cathode, means for preventing regeneration due to said gridanode capacity comprising a tuned circuit connected between grid and anode and tuned syntonously with said timed input circuit.

13. The combination with a vacuum tube 'having a plurality of electrodes between two of which electrodes there is a capacity tend ingito produce regeneration, of a source of oscillations of a certain frequency, and means comprising a circuit resonant to said certain frequency connected between said two electrodes and coupled to said source of oscillations for neutralizing the regenerative capacity eect between said two electrodes for said certain frequency.

M. The combination defined in claim 9, including also a wave source, and means for coupling said wave source to each of said tuned circuits.

15. The 'combination defined in claim 9, including also an incoming circuit coupled to the inductances of each of said timed circuits and poled with respect thereto to produce excitation therein 'in opposing phases.v

In witness whereof, I hereunto subscribe GEORGE sTEvENsoN.

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