US1933773A - Rectifier system - Google Patents

Description

Nov. 7, 1933. F, TERMAN 1,933,773

RECTIFIER SYSTEM Filed Dec. 23, 1929 INVENTOR. EFmDM/IQK 5, gwma/w,

' ATTORNEY 1 20 to be rectified is impressed across the plate and mission.

Patented Nov. 7, 1933 I UNITED STATES. mm

RECTIFIER SYSTEM Frederick E. Terman, Stanford University; Calif., assignor to Wired Radio, Inc., New York, N. Y., a corporation of Delaware Application December 23, 1929 Serial No. 416,173

9 Claims. (Cl. 250-27) My invention relates broadly to electron tube structureis one important controlling condition rectifiers and more particularly to an inverted in this respect, and such operation is facilitated electron tube circuit arranged to operate as a if the incoming signal is weak. The operation rectifier. will be better understood by reference to Fig. 6

One of the objects of my invention is to pro of my Patent No. 1,846,0 i3, which shows a com- 60 vide an improved rectifier circuit having a stepplete static characteristic curve of grid current down voltage characteristic whereby relatively plotted against plate voltage. The energy to be large potentials of alternating characteristic rectified is impressed across the plate and cathmay be impressed across the rectifier circuit for ode electrodes while the rectified energy is dederiving a rectified current of relatively small rived in the circuit connecting the grid and 65 amplitude, cathode electrodes. The step-down voltage Another object of my invention is to provide ratio obtainable in the electron tube system is a rectifier or detector circuit which may be subdependent upon the structure and design of the jected to relatively large potentials for obtainelectron tube employed. In my copending aping stabilized rectifier or detector operation with- .plication Serial No. 413,555, filed December 12, 70 out reaction due to the relatively large I im 1929,.entitled Electron tubal have illustrated pressed potential. certain constructions. of electron tubes which A further object of my invention is to promay be employed in the circuit arrangement of vide a system of rectification wherein the energy my invention to secure the desired voltage transcathode electrode of a three element tube and In Fig. 1, I have illustrated a modified form the rectified energy derived in an output cirof circuit arrangement embodying my invention cuit connected to the grid and cathode elecwherein a highresistance leak path is protrodes of the electron tube system. vided in series with the plate electrode of, the

5 Other and further objects of my invention electron tube system which includes electron 80 reside in the circuit arrangement for an electube 1 having cathode 2, grid electrode 3 and tron tube rectifier set forth more fully in the plate electrode i. The cathode is heated from specification hereinafter following by reference battery system 5. The output circuit includes to the accompanying drawing, wherein: battery 6 having one terminal thereof directed 3 Figure 1 illustrates one form of rectifier systoward the grid electrode 3 in such manner that tom embodying the principles of my invention; through the output load a positive bias and Fig. 2 illustrates a modified circuit arrangeis maintained on the grid 3. In series with'the ment for the rectifier system of my invention. plate circuit there is disposed a condenser '7 In the circuits of my invention I employ the shunted by the high resistance leak path 8 by 35 principle of the inverted electron tube as set which the energy to be rectified is supplied to go forth more fully in my copending application the plate electrode {l and in circuit with cathode Serial No. 405,363, filed November 7, 1929, now 2. The input current ficwingin the plate cir- Patent No. 1,846,043, issued February 23, 1932, cult must pass through this condenser unit and and entitled Electron tube circuit. The input produces a d rect current voltage drop between 40 system for the electron tube employed in my cathode and plate which iseffective in varying 95 invention connects between the plate and caththeelectric field between cathode and grid, and ode electrodes while the output system in the hence varies the output current delivered by the electron tube of my invention connects between grid. The energy to be rectified is supplied the grid and cathode electrodes. The-plate elecacross the leads designated at 9. The rectified i5 trode may be normally'maintained at negative energy is delivered acrossthe'leads designated 1 0 potential while the grid electrode is normally at 10. Rectification may be said'to occur in the maintained at positive potential. It is also posplate circuit or input circuit. The rectification sible to operate the system of my invention withoccurs because the characteristic curve of plate out applying a direct current biasing voltage to current against plate voltage is not linear.

the plate since the characteristic curve of an Since grid 3 is maintained at a potential posi- 5 inverted three electrode tube showing grid curtive with reference to cathode 2, adirect current rent plotted against plate voltage shows a very 'will flow from cathode- 2 through source. 6, sharp peak at the point'of zero plate voltage. through load 10, and to grid 3. The electron Conditions should beso maintained that subflow between cathode and grid .Will be varied stantially no plate current will flow; the tube by the variations in the electric field between. 11

cathode and grid caused by the variations in the input potential impressed between plate and cathode. The current flowing to the positive grid depends upon the electric field existing between cathode and grid, and is substantially independent of how this field is produced. Both the grid and plate potentials affect the magnitude of this field.

In Fig. 2 I have shown an arrangement of rectifier circuit in which the input system includes biasing battery 12 for normally maintaining the plate 4 at negative potential. Relatively high potentials impressed across the circuit 9 are rectified and producerelatively low rectified current at the terminals 10 for distribution to the load.

No current fiows in the plate circuit because the plate is negatively biased. This bias should be adjusted to the portion of the characteristic curve of suitable curvature. The alternating voltage impressed between plate and cathode will vary the electric field between plate and cathode, including the electric field between grid and cathode, and hence will vary the output current delivered by the grid. I have usually found greater sensitivity by employing the condenser and leak in the plate circuit with little or no plate bias. The higher the resistance of the plate leak, the more sensitive the detection.

In both forms of the circuits as described, the direct current output derives its essential energy from the gridbattery 6. The direct current flowing in the grid circuit is, however, varied or controlled in accordance with the alternating voltage impressed between plate and cathode. The type of rectification obtained by the arrangements shown in Figs. 1 and 2 is analogous to the rectification obtained in the normal type of detector circuit with the usual three electrode tube applying the input to the grid and delivering output from the plate...

Fig. 1 corresponds to the ordinary type of grid-leak grid-condenser detection with normally operated tube in which the applied signal voltage is rectified by the non-linearity of the grid-filament circuit, producing a rectified grid current that must fiow through the grid-leak grid-condenser impedance and produce a voltage drop, which in turn affects the plate current o'i' the tube by ordinary amplifier action, as described in my paper which appeared in the October 1928 issue of the Proceedings of the Institute of Radio Engineers, vol. 16, page 1384.

Fig. 2 corresponds to the usual type of detector circuit with normally operated tube employing a negatively biased grid battery wherein rectification may be said to occur in the output or plate circuit. In the system of my invention, particular methods are employed for applying the inverted electron'tube to detector circuits heretofore known with normally operated tubes having input connected to the grid and output connected to the plate. It should be particularly noted that in the system of my invention, no substantial portion of the output energy is derived from the alternating current input but that substantially all of the output energy is derived from the grid battery 6. In the inverted vacuum tube system of my invention, an alternating current applied to the plate has the same effect on the output or grid current as though a potential of similar wave form but much less voltage had instead been added to the grid batshown in Fig. 2, rectification takes place in the output or grid circuit.

In leak condenser rectification, as shown in Fig. 1, the rectification results from the nonlinear relation that exists between the plate current and the plate voltage when the plate poten tial is at or near zero volts with respect to the cathode. With detection of this type, the relationship between positive grid voltage and grid current is preferably linear. Leak condenser rectification always takes place with a grid current which increases as the voltage being rectified becomes greater. In contrast with this anode current rectification with the inverted tube makes use of the non-linear relation that exists between anode current and anode voltage when the plate is biased with a relatively high negative potential that approaches the cut-off condition. Anode rectification of this type takes place entirely in the anode circuit and is not accompanied by the presence of grid current unless the rectifier is overloaded. Anode rectification can only take place when the operating conditions are such that the anode current and anode voltage have a non-linear relation.

While I have described the rectifier and detector circuits of my invention in certain preferred embodiments, I desire that it be understood that modifications may be made and that no limitations upon my invention are intended other than are imposed by the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent oi the United States is as follows:

1. In a rectifier circuit an electron tube including cathode, grid and, plate electrodes, an input circuit connected across said plate and cathode electrodes, an output circuit connected across said grid and cathode electrodes, a source of energy connected for applying a positive potential to said grid with respect to said cathode, and means connected in circuit with said plate electrode for determining the operation of said electron tube as a rectifier whereby potentials supplied across said plate and cathode electrodes for charging said grid electrode at positive po-' tential whereby relatively high potentials impressed across said input circuit are stepped down, rectified, and the rectified current delivered at lower amplitude to said output circuit.

tube including cathode, grid and plate electrodes, an input circuit interconnecting said plate and cathode electrodes, an. output circuit interconnecting said grid and cathode electrodes, meansfor maintaining Said grid electrode at positive" potential, and a reactance connected in circuit with said plate electrode in said input circuit whereby relatively high potentials impressed across said input circuit are stepped down, rectified and the rectified current of relatively low amplitude delivered to said output circuit.

4. In an inverted electron tube rectifier system, an electron tube having at least one cathode, one grid, and one plate, a source of alternating cur- 3. A rectifier system comprising an electron rent to be rectified connected to said plate and said cathode, a source of direct current grid potential, and an output circuit connected through said source of grid potential to said grid and said cathode for applying to said grid a potential positive with reference to said cathode.

5. In an inverted electron tube rectifier system, an electron tube having at least one cathode, one grid, and one plate, a source of alternating ciu'rent to be rectified connected to said plate and said cathode, means connected in series between said source and said plate and cathode for maintaining said plate at a determined potential with reference to said cathode, a source of direct current grid potential, and an output circuit connected through said source of grid potential to said grid and said cathode for applying to said grid a potential positive with reference to said cathode.

6. In an inverted electron tube rectifier system, an electron tube having at least one cathode, one grid, and one plate, a source of alternating current to be rectified connected to said plate and said cathode, a condenser connected in series between said source and said plate and cathode, a high resistance connected in shunt with said condenser, a source of direct current grid poten tial, and an output circuit connected through said source of grid potential to said grid and said cathode for applying to said grid a potential positive with reference to said cathode.

7. In an inverted electron tube rectifier system, an electron tube having at least one cathode, one grid, and one plate, a source of alternating current to be rectified connected to said plate and said cathode, a source of'directcurrent powith respect to said cathode, asource of direct current grid potential, and an output circuit connected through said source of grid potential to said grid and said cathode for applying to said grid a potential positive with reference to said cathode.

8. In a rectifier system employing a three electrode electron tube, the method of rectification which consists in applying the voltage to be rectified between the plate and cathode of said tube, maintaining said plate at a negative potential with reference to said cathode, maintaining said grid at a positive potential with reference to said cathode, and delivering the output of said system from said grid andsaid cathode.

9. In a device of the class described, an electron tube having at least three electrodes, namely a plate, a cathode and a grid, an input circuit conductive of alternating potentials and connected between said plate and said cathode, an output circuit including a source of energy for positively biasing said grid with respect to said cathode and connected between the two electrodes last mentioned, and meansincluding the structural arrangement of said electrodes and the provisicnof a zero-bias applied to said plate with respect to said cathode for causing said alternating potentials to produce a rectifying control of the currents in said output circuit.

FREDERICK E. TERMAN.

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