US2292439A - Stabilized electron discharge device circuit - Google Patents

Description

Aug. 11, 1942. Q icKE 2,292,439

' STABILIZED ELECTRON DISCHARGE DEVICE CIRCUIT Filed Aug. 19, 1940 2 Sheets-Sheet 2 3a Z I 30 :L\ as iv 4: 24 Q INVENTOR v ROMAN OL/C/(E ATTORNEY Patented Aug. 11, 1942 I 1 STABILIZED ELECTRON DISCHARGE DEVICE CIRCUIT Roman Golicke,'Falkensee, Germany, assignor to Fides Gcsellschaft fur die Verweltung und Verwertung von gewerbllclien Scliutzrechten mlt beschri'mkter Haftung, Berlin, Germany, a corporation of Germany Application August 19, 1940, Serial No. 353,296

6 Claims.

This invention is concerned with a circuit arrangement designed to reduce the actions of fluctuations of the operating potentials and variations in tube data as a result of aging, particularly upon frequency stability in multi-grid tubes. It is known that great constancy of frequency in a generator tube is obtainable by insuring feedback under favorable phase conditions and' by operating the oscillator so that distortion is avoided. In order to satisfy these demands to be made in operating a transmitter of stable frequency in so far as the tube itself is concerned, circuit schemes have been developed in which the real tube quantities variable under routine operating conditions will affect the frequency only to an extremely insignificant degree. However, it has been ascertained that variations of the working voltages may nevertheless react upon the frequency. These residual influences, for instance, are ascribed to variable components of the internal tube capacitance which are acted upon by the potentials prevailing at the electrodes and by the emission of the cathode by way of the space charge.

It has been ascertained that variations or fluctuations of the working voltages at the various electrodes of the oscillator will, in part, affect the frequency in contrary directions. In the circuit organization of thi invention which is especially designed to insure constant and stable frequency in a multi-grid oscillator tube, the variations of the plate potential are distributed among the various tube electrodes in such proportions that mutual compensation of the working voltage variations will be insured. The com-- Germany August 18, 1939 (Granted under the provisions of sec. 14, act of March 2, 1927; 357 0. G.

cathode. Inserting in the bridge resistances of a type having voltage effect, that is to say, resistances being a function of potential, then conditions maybe shaped in such a way that upon variations of the plate potential the voltage impressed upon the flrst grid will change in such a way that frequency fluctuations are compensated. The sign of. the variations reaching the first grid may, according to requirements, be chosen at will by choosing the arrangement of the voltage-dependent resistances in the bridge accordingly. Among the resistances comprised in the bridgescheme, all or merely a part thereof may be of the kind which in their operation are a function of the potential. In order that the plate potential variations may be regulated or eliminated as far as feasible in the absence of inertia, it is expedient and advantageous to us a glow-discharge tube, for instance, for one of the voltage-dependent resistances. Inasmuch as the grid adjacent to the cathode has preferably potentials that are negative to the cathode, the control action may be made non-dissipative (wattless) Hence, for regulation only extremely small currents are required so that the voltagedependent resistance may consist of a small signal glow tube.

Simultaneously with the compensation of the plate potential variations, it is possible also to obpensating potentialis preferably applied to one or moreelectrodes adjacent to the cathode and which have a potential which is negative in respect to the cathode so that control free from dissipation is feasible. The working voltage fluctuations'which affect the electrodes are so assessed in reference to one another that frequency fluctuations will oifset one another.

The voltage or voltages required for compensation may be advantageously obtained in a bridge circuit scheme. tials are most suitably derived from the plate lead, the tube and a resistance, on the one hand, and two resistances, on the other hand, constituting the arms of a bridge arrangement. One of the diagonals of the bridge is fed from the plate potential, whereas the other diagonal accordingly results in a controlling direct current voltage which may be impressed, for in-- The compensating potentain compensation and equalization of the fluctuations of cathode emission. These fluctuations of emission of the cathode may be occasioned,

for instance, by fluctuations in the heating as well as by aging of the cathode. For stabilization of the emission, a control potential counteracting the fluctuations of emission may be impressed upon the grid or the same electrodes which serve for compensating the plate potential fluctuations. Such stabilizationis accomplishabl, for instance, by the drop of voltageacross a resistance included in the lead brought to the cathode. In order to maximize the effectiveness of this scheme, the resistances are preferably so proportioned that a large part of the plate potential will be in thedrop of potential across the cathode resistance. The first grid must then be impressed with'a positive counteracting potential. v

A circuit organization as here disclosed is generally suited for multi-grid tube circuits in which only part of the tube electrodes is used for signal circuit purposes, while other electrodes, for instance, the first grid; are available for compensating or stabilizing purposes. For example,

stance, upon the grid of the tube adjacent to the generators opera w Series r a ce circults (also low-ohm oscillator crystals) may be designed. Since in such schemes the resonance circuit is in low-ohm connection with. the tube,

the reactions of the tube upon the frequency are anyway low. of the said sort may frequency constancy.

Hence, crystal stabilized oscillators be expected to insure high The invention shall now be explained in more as to frequency by means of the invention, and

Figs. 3, 4, 5 and 6 illustrate different embodiments of the invention.

Fig 1 shows a generator comprising a multigrld tube in which by means of a feed back condenser Cr and grid leak resistance R. of suitable value, regeneration of strict phase is assured. The compensating potential in this generator may preferably be impressed upon the grid G1 adjacent to the cathode. For it has been ascertained that voltage fluctuations at the first grid influence the frequency more strongly and in the opposite sense as compared with most other electrodes. r

Fig. 2 illustrates an oscillator which works in combination with a series resonance circuit. The frequency is here determined by a crystal K. Compensation of the plate potential fluctuations is effected also by way of the grid G1 which is adjacent to the cathode.

An exemplified embodiment of a simple circuit arrangement for compensation of plate potential influences. upon the frequency is schematically shown in Fig. 3. What is here used is a bridge scheme, tube l and the resistance R1 comprising the two fractional resistances 2 and 3, on. the one hand, and the resistances 4 and 5, on the other hand, constituting the four arms of the bridge. One of the diagonals of the bridge is fed with plate potential Us, while the other diagonal feeds a controlling direct current voltage to the first grid G1 of tube l. Inserting in the bridge voltage-dependent resistances, then conditions may be made so that upon variation of the plate potential Us the voltage acting upon the first grid is so altered that frequency variations are eliminated and compensated. It has been found to be advantageous to apply almost the entire fluctuation of the plate potential upon the first grid G1. Hence, the resistance 4 (or resistances 2 and 3) must be of such nature that current variations will occasion only slight potential variations, and/or resistance 5 is to exhibit the opposite behavior. In a great many instances it is sufficient to make only one of the three resistances voltage-dependent. In order that potential variations of the plate may be eliminated as far as feasible without inertia, it is of advantage to use a glow-tube in lieu of the resistance 6. Since the first grid is at a negative potential in reference to the cathode, the control action may be non-dissipative and wattless. The bridge arms'consisting oi the resistances t and 5, as a consequence, have to carry only very small currents; hence, small signal lamps could be used, for instance.

Fig. 4 shows an exemplified embodiment for a regenerative oscillator of very high frequency stability. One pair of bridge arms for the regulating potential is here divided into two parallel potentiometer 9 by way of a slide contact it, this potentiometer uniting the two parallel portions of the bridge am. By the aid of the potentiometer 9 it is possible te -regulate the proportion of the plate potential fluctuations which is impressed upon the first grid, this proportion being greater the closer the slider ill comes to be placed to that end of the potentiometer turned towards the glow-tube.

' Aside from the effects of the plate potential upon the frequency, also the reactions of the cathode whose emissivity fluctuates as a function of the heating and the age, are neutralized. For stabilizing the space current there is provided a cathode resistance which is formed by the resistances l2, It.

In the case of an oscillation generator as shown in Fig. 4, frequency stability is enhanced further on account of the fact that the coupling of the consumer or load is made as low as possible in reaction. This is readily feasible in the case of multi-grid tubes, without it being necessary to provide a special isolation stage. For instance, the oscillation circuit means may be con-.

nected to grids which are shielded from the plate serving as the output by an electrode being at zero alternating potential. It has been ascertained that-in hexodes the screening effect afforded by the fourth grid is not quite adequate to insure complete decoupling. In the case of the generator shown in Fig. 4, therefore, neutralization is provided by deriving from the output transformer or output oscillation circuit a1- ternatlng voltage presenting a phase shift of 180 to the plate potential, the said potential by way of a small neutralizing condenser It being impressed upon the oscillatory circuit consisting of the inductance coll L and capacity C. If the neutralization is accurately adjusted by the aid of the variable condenser l4, actions upon the frequency by fluctuations of the output load will be largely avoided.

In the exemplified embodiments of circuit arrangements shown in Figs. 3 and 4, cheer two of the cathode resistances 2, 3, and l2, l3, re-

spectively, may be made variable within certain limits. Thus the cathode current to which stabilization becomes adjusted can be altered. And thls in turn, will vary the slope of the characteristics of the utilization or signal circuit organization. I

In the case of oscillators, such regulation isof advantage in order that the feed back by way of the slope may be so adjusted that operation will be only inside the steeper portion" of the doubly curved characteristic, and this portion lies inside the region of negative potentials.

Grid current fiowtogether with its harmful effects upon frequency stability arethus avoided.

Fig. 5 shows a frequency stabilized generator. For frequency generation there are here used two multi-grid tubes l5 and I6 operating in pushpull. Between the plates of these tubes there is inserted the oscillation circuit comprising the inductance l1 and the capacity 3.. The output end is in coupling relation with the said oscillation circuit by wayof the coil is. The utilizaportions, one of these containing the glow tube I tion or signal voltage is taken off across the terminals 20 and 2|. In this circuit arrangement it is advantageous to use separate cathode resistances 22 and 23, for in this manner each cathode can be stabilized separately. These resistances are most conveniently made variable. For joint regulation of the cathode current and thus of the slope or mutual conductance of both plate potentialfiuctuations independently of each tubes may serve a'common portion of the cathode resistances, say, the variable resistance 24.

Potentiometer 25 is inserted between two voltage dividers which are a function of potential'in opposite directions. One of the said voltage dividers comprises the resistance 28 and the glow tube 21, the latter preferably having in series another resistance 28, while in the case of the other, voltage divider and glow tube are transposed. i

In this arm, the glow tube 29 is connected with the positive terminal 30 of the plate potential.

Connected with the negative terminal 3| is the resistance 32. Glow tube 29 may besides have connected'in series with-it a resistance 33. Owing to the fact that the potentiometer 25 is included between two voltage dividers being a function of potential in contrary directions, it is possible to adjust the compensating potential both as to amount as well as of sign. The condensers 34 to 28 are so proportioned that they result in a block for the working frequency.

Fig. 6 illustrates by way 01' example a measuring organization comprising the use of stabilizing means according to the invention. This arrangement may serve, for instance, for the measurement of small direct current powers under conditions free from dissipation. The instrument 49 in this scheme is connected in a bridge between two tube paths. The instrument current is only a small fraction of the tube currents; for instance, for full deflection it may amount to 100 a amp., as contrasted with -10.

milliamp. electrode current. By virtue of this ratio between instrument current and tube current changes of tubes become very manifest and must be "eliminated by the adoption of special measures to this end. A

The direct current voltage to be measured is impressed upon the terminals 38 and 40. Adjustment of zero of the instrument is roughly possible by choosing suitable fixed resistances 4| and 42. Fine adjustment is accomplishable by variation of the, positive potential impressed upon the fourthgrid G4 of tube 43 by way of the potentiometer 44. Potentiometer 45 serves for compensation of the plate or heating potential varia! tions. While by resistances 4| and 46 stabilization of the cathode is attained, the residual infiuences of the cathode are eliminable by the-aid of a compensating voltage impressed'upon the third grid in series with the utilization (signal) control potential which may be taken oil from a potentiometer 45. At this potentiometer 45 acts the stabilization potential for the first grid Gi.

Resistance 42 in this connection may be chosen of small value; it merely serves the purpose to provide a dropof potential which corresponds to the difference-of the biasing potentials of grids G1 and G3. Compensation of the cathode actions can be secured to a large degree if a suitable fraction of the stabilizing potential is tapped on the potentiometer 45 and impressed upon the grid G3.

By suitable adjustment it would also be possible to compensate at the same time plate potential fluctuations if the plate potential and the heating or cathodepotentialoriginate from r the same source ofenergy supply so that their fluctuations would be similar. However, such a step would fail to take care of such cathode fluctuations as are caused by aging of the cathode. Hence, it is expedient to insure cathode stabilization or compensation and compensation of the other.

Compensation of the plate potential fluctuations is feasible because of the fact that plate current and grid current of grid G2 are made to like measure a function of the plate potential.

The plate and G: paths are mostly resistances which are a function of potential to unequal extents. Thus, in order to render their voltage dependence alike, the path involving the greater voltage dependence has an ohmic resistance of suitable size connected in parallel with it.

Resistances 4i and 42 are suitably so chosen that when operating the potentiometer 45, the shifts in the operating point will be as small as possible. chosen so large that shifts in the operating point as well as disparities in tube data and characteristics can be aligned and compensated. Through arm 44, 41, 42 and 48 roughly the same current may flow as through the tube. In this instance, resistance 48 becomes approximately equal to resistance 48. In order that the amplification may be made as high as possible, the resistances 46 and 48 may be made as low as compensation will just permit. The potentiometer may be one order of magnitude approximately higher in ohmage than these resistances; for instance, of

a value of 500 to kohm.

' What is claimed is:

1. An oscillator circuit comprising a multi-grid electron discharge device having a cathode, a first grid adjacent said cathode and separated therefrom solely by space, an anode, and a plurality of intermediate electrodes; an oscillatory circuit coupled between two electrodes of said device other than the first grid; a source of potential connected between said anode and cathode; a non-linear resistance network bridged across said anode and cathode; and a connection from the first grid of said device to "a point on said network so chosen that changes in the potential of said source tending to produce a change in the frequency of oscillation will apply to said first grid potentials of such magnitude and sign as to substantially neutralize the tendency to frequency 2. An oscillator circuit comprising a multi-grid electron discharge device having a cathode, a first grid, an anode, and a plurality of intermediate electrodes; an oscillatory circuit coupled between two electrodes of said device other than the first grid; means for biasing said first grid negatively relative to said cathode; a source of potential connected between said anode and cathode; a non-linear resistance network bridged across said anode and cathode; and a connection from the first grid of said device to a point on said network so chosen that changes in the potential of said source tending to produce a change in the frequency of oscillation will apply to said first grid potentialsof such magnitude and sign asto substantially neutralize the tendency to frequency change caused by the changes in potential of said source. v

3. An oscillator comprising a multi-grid electron discharge device having a cathode, first, second, third grids and an anode; means for biasing said first grid at a negative potential relative to said cathode independently of the generated oscillatory currents; an oscillatory circuit coupled between said second and third grids; a source of potential connected between said anode and cathode for maintaining said anode at a positive po- The potentiometer 44 is preferably and first grid, the point oi connection from said first grid to said network being so chosen and .the resistors oi said network having such values that changes in the potential oi said source tending to produce a. change in the frequency oi oscillation will apply to said first grid potentials oi such magnitude and sign as to substantially neutralize the tendency to irequency change caused by the changes in potential of said source.

4. An oscillator in accordance with claim 3-, characterized in this that said oscillatory circuit comprises a parallel tuned circuit connected between said second gridand said cathode, there being a feed -back reactor coupling said third grid and said oscillatory circuit 5. An oscillator in accordance with claim 3, characterized in this that one of the resistors of sistors connected in series between the cathodeand the negative terminal oi said source; and a connection irom said iirst grid to the junction point oi said first pair oi resistors, the values oi said resistors being so chosen that changes in the potential oi said source tending to produce a change in the irequency oi oscillation will apply to said first grid potentials oi such magnitude and sign as to substantially neutralize the tendency to frequency change caused by the changes said network is voltage-dependent and comprises as in potential oi said source.

a glow tube.

6. An oscillator circuit comprising a multi-grid ROMAN GOLICKE.

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