US2027160A - Vacuum tube oscillator - Google Patents

Description

Jan. 7, 1936. R. E. FURAY 2,027,160

' VACUUM TUBE OSCILLATOR Original Filed Jan. 18, 1932 PW? .URRENT.-' J;

CONTROL VOLTAGE.

IN VEN TOR RICHARD FURAK" ATTORNEY Patented Jan. 7, 1936 VACUUM TUBE OSCILLATOR Richard E. Furay, San Francisco, Calif.

Application January 18, 1932, Serial No. 587,230 Renewed September 26, 1933 17 Claims.

an oscillator wherein the frequency-determining 1o circuit is not called upon to supply current to the load circuit; to provide an oscillator wherein the frequency-determining circuit is substantially symmetrical; to provide a vacuum tube oscillator wherein the load imposed on the tube by the os- 15 cillating circuit is substantially constant through out the cycle of-oscillation; to provide a vacuum tube oscillator wherein the potential of the control elements is automatically varied to compensate for changes of anode potential; and, con- 20 sequently, to provide an oscillator which is substantially unaffected in frequency by relatively large changes of supply current and potential.

Other objects of this invention will be apparent or will be specifically pointed out in.the descrip- 25 tion forming a part of this specification, but I do not limit myself to the embodiment of the invention herein described, as various forms may be adopted within the scope of the claims.

Referring to the drawing:

30 Figure 1 is a vertical sectional view of the vacuum tube of my invention.

Figure 2 is a plan view of the tube elements, the plane of projection being indicated by the line 2--2 of Figure 1. e

Figure 3 is a schematic circuit diagram of the oscillating circuit of my invention, embodying the tube shown in the first two figures.

Figure 4 shows the characteristic curves of the tube, indicating the operating range thereof when 40 used in the circuit of Figure 3.

My invention comprises an oscillator embody- V in a vacuum tube having a plurality of control elements which may be operated so that changes in the potential thereof have opposite effects upon 45 the plate current, i. e., wherein the negative swing of potential of one of the control elements increases the output current, while a similar swing of the other element decreases the output current. The two control elements are connected by a par- 50 allel-tuned circuit, which is coupled to the plate of the oscillator tube. The frequency of oscillation is determined almost wholly by the tuning of the parallel circuit connecting the two control elements. The tube preferably used comprises 55 the usual filament, plate, and grid-control e1ement mounted between filament and plate, and an additional control element, which I have termed a reflector, positioned on the opposite side of the filament from the plate. When operated at a proper positive potential the two 5 control elements have opposite effects on the plate current, as above stated. This positive potential is preferably derived from the plate circuit through a resistor. With this arrangement the control-element potential is a function of the plate potential, varying with it in such a manner that variations in plate current or voltage are almost completely compensated and a high degree of frequency stability is secured even though the supply sources feedingthe tube may vary. '15

A preferred form of my device utilizes a tube havingthe usual envelope I having a stem 2 upon which the elements of the tube are mounted. Sealed through the stem are a pair of filament leads 3, 4, a plate support and lead 5, and a grid support andlead 6. The stem also carries a' plurality of supports or dummies I, 9, I0 and H, to which are attached the various elements of the tube as will be described.

The supports 6, 1,9 and II extend toward the top of the tube to above the elements, and secured to their upper ends are a pair of insulating bars I2, preferably of glass, which tie the supports together to form a rigid structure, and to each of these bars is secured a spring hook I 4.

The filamentary cathode I5 of the tube is mounted substantially in a plane, and extends from the lead 3 up over one of the hooks l4, thence toward the stem 2 where it is hooked over a dummy l6 mounted in the stem, thence up and over the second hook I4 and back to the lead 4.

The plate I1 is positioned substantially parallel to the filament and is mounted on the lead 5 and dummy or support II), the top of the plate being steadied. by the short wires l9 which are 40 sealed into the insulating bars I2. I

A planar grid 20 is positioned between the cathode and the plate, and comprises parallel wires extending between supports 6 and 9. This grid acts in the manner familiar in the ordinary triode construction, and can take almost any of the many forms which have been developed for this purpose.

Positioned on the opposite side of the filament from the grid is the control plate or reflector 2 I, which is secured to the wires I and I I. The lead to this element, in the form of the device here shown, is a wire 22 which is sealed through the tip 24 of the tube.

The two control elements 20 and 2| are symmetrically placed with respect to the plate, and hence have different effects upon the plate current as is shown by the curves of Figure 4. The curve 25 illustrates the effect of varying the potential of the grid 20 with the reflector main tained at zero potential. Curve 26 shows the effect on the plate current of varying reflector potentials with the grid maintained at zero. With different potentials on either control a family of curves may be drawn for the other control element, each curve of the family being substantially parallel to the others and having maxima and minima at substantially the same control voltages, although these maxima and minima are of different values for the different curves.

It will be seen that for relatively lowcontrol voltages the effect of the two control elements is in the same direction, i. e., for voltages less than those indicated by the dotted line a the plate current increases with increasing potential. At the control voltage a and above, increasing the potential of the reflector decreases the plate current, Whereas increasing the grid potential increases the plate current. At a much higher positive potential the effect of increasing the grid potential also reverses, in the range higher than that indicated by the dotted line b of the graph. The operating range of this device is between the control voltages indicated by the lines a and b.

The tube is preferably operated in a circuit whose preferred form is shown in Figure 3. The filament I5 is heated by a suitable source 33. The grid 2!] and reflector 2! are connected at opposite ends of a parallel-tuned circuit comprising an inductance coil 3! and variable condenser 32. The plate I! is connected through a second parallel-tuned circuit, comprising an inductance 34 and variable condenser 35, to a suitable plate supply 36 and thence back to the filament. The two parallel-tuned circuits are coupled, preferably by means of a high resistance 3! shunted by a by-pass condenser 39, this coupling circuit being preferably connected to the two inductances by variable taps 40 and 4! respectively.

Since both of the control elements are operated at positive potential, each of these elements will draw current. This current, flowing through the resistor 31, causes a potential drop, so that the control elements operate at a potential lower than the plate but which is a definite function of the plate potential. The magnitude of this resistor and the potential drop will, of course, vary with the size of the tube and with the plate potential, but the correct size for this resistor may readily be deduced from the operating characteristics of the particular tube, the resistor being so chosen as to bring the mean operating potential of the two control elements midway between the control potentials a and b of Figure 4.

The positive control element potential also has the effect of reducing the output impedance of the tube to a much lower value than would obtain with a tube of comparable dimensions operated at a negative bias. This leads to high plate circuit efiiciency, and, since the mean control potential is substantially constant, does not introduce wave form distortions which are objectionable.

Since the filament, which may be considered as ground potential, operates midway between the grid and the reflector, there will be a node of potential approximately midway between the ends of the coil 3|. The adjustable tap M is displacedslightly from this potential node. The coupling of the two oscillating circuits is determined by the position of both of the taps M3 and ll, these taps being preferably positioned to give the minimum coupling at which stable operation occurs.

In the operation of the device the frequency is determined almost entirely by the tuning of the parallel tank circuit comprising the inductor 3i and condenser 32, it being possible to vary the tuning of the plate circuit through wide limits without material frequency variations. The effect of the plate circuit tuning does, of course, vary the intensity of the oscillation and the energy output, but until this circuit is thrown so far out of tune that the coupling back to the control tank circuit is almost entirely out of phase, oscillation will still take place with a frequency variation of substantially nil.

The control element circuit is, in fact, almost self-oscillatory. The current drawn from this circuit is only that to the control elements ofthe tube, however, and since these elements are varying in opposite directions at the same time this load is substantially a constant regardless of the oscillating power withdrawn from the plate circuit of the device. cient to account for the remarkable frequency stability of the circuit, and the supply of the positive grid potential as a function of the plate voltage is a factor which increases this stability.

In practice the device has been found to work :1

pacity of the two control electrodes in opposite 5 directions, so that the net input capacity of the tube varies little with changing load.

Those familiar with modern vacuum tube practice will at once recognize that various modifications in the method of coupling the tuned circuits and in applying the positive of bias to the control element are possible without affecting the operation of this device. I therefore do not desire to be limited by the exact form shown, but wish to protect the invention as defined in the following claims.

I claim:

1. A vacuum tube oscillator comprising the combination with a vacuum tube having an output electrode and a pair of control electrodes, of 1 means for biasing said control electrodes to produce opposite effects on the magnitude of current flow through the tube tosaid output electrode with similar variations of control potential, 2.

parallel resonant circuit connecting said control electrodes, and a resonant circuit in series with said output electrode and coupled'to said first mentioned circuit.

2. A vacuum tube oscillator comprising the combination with a vacuum tube having an output electrode and a pair of control electrodes, of means for biasing said control electrodes to produce opposite effects on current flow through the tube to said output electrode, a parallel resonant circuit connecting said control electrodes, a resonant circuit in series with said output electrode, and a connection joining non-nodal points of said circuits.

3. A vacuum tube oscillator comprisingthe combination with a vacuum tube having an outi This fact is, of itself, sufiia parallel resonant circuit connecting'said control electrodes, a resonant circuit in series withsaid output electrode, means for maintaining said output electrode at a positive potential, and a resistive connection between said resonant circuits for coupling said circuits and maintaining said control electrodes at a lower mean positive potential to produce opposite effects on current flow through the tube to said output electrode.

4. An oscillator comprising the combination with a vacuum tube having a cathode, an anode,

a grid control electrode, and an additional control electrode, of a parallel resonant circuit connecting said control electrodes, a second parallel resonant circuit in series with said anode, a resistor connecting said circuits intermediate their ends for supplying a positive potential lower than the anode potential to said control electrodes to produce opposite effects on current flow through said tube to said anode, and a condenser bridging said resistor for coupling said circuits.

5. The combination with a vacuum tube having a cathode, a plate positioned on one side of said cathode, a control grid between said cathode and plate, and a second control element in the form of a reflector on the opposite side of said cathode, of an oscillating circuit comprising. a parallel resonant circuit connecting said grid and reflector, a second parallel resonant circuit in series with said plate and said cathode, means for maintaining said plate at a positive potential, means for maintaining said reflector at a lower positive potential to produce a current between said cathode and anode in opposite sense to said grid, andmeans for coupling said parallel resonant circuits.

6. The method of producing electrical oscillations having a high degree of frequency stability which includes the steps of generating an electron fiow, causing said fiow'to produce two oppositely varying control potentials, governing said flow with said potentials, and maintaining said potentials within a range wherein opposite variations of said potentials produce like effects on the magnitude of said flow.

7. The method of utilizing a vacuum tube having two control electrodes to produce electrical oscillations having a high degree of frequency stability which includes the steps of causing an electron flow within said tube, maintaining bias potentials 'on said control electrodes such that opposite changes in said potentials will produce like effects on the magnitude of said flow, and

- causing variations in said flow to vary oppositely the potentials of said control electrodes.

8. The method of producing electrical oscilla- 4 tions having a high degree of frequency stability which comprises the steps of establishing an electron flow, causing variations in magnitude of said'fiow to produce two oppositely varying potentials and causing said potentials cumulatively to effect said changes in magnitude of flow.

9. The method of producing electrical oscilla- L tions having a high degree of frequency stability which comprises the steps of establishing an electron flow, causing variations in magnitude of said flow to produce two oppositely varying potentials causing said potentials cumulatively to effect said variations in magnitude of flow, and storing and releasing energy derived from said flow in time with the variations thereof and applying the potential of said stored energy to increase said first mentioned potentials.

10. A vacuum tube oscillator comprising the combination with at least one vacuum tube having an output electrode and a pair of control electrodes, of means for biasing said control electrodes to cause like changes in the respective potentials thereof to produce opposite effects on the magnitude of current flow through the tube to said output electrode, a tuned oscillating circuit connecting said control electrodes, and an output circuit connected to said output electrode and coupled to said tuned circuit.

11. In combination, an input circuit, vacuum tube relaymeans comprising an output electrode anda pair of control elements, said control elements being connected to said input circuit in opposed phase relationship, means for biasing said control elements to cause opposite potential changes impressed thereon to produce cumulative current-magnitude changes in said relay means, an output circuit connected to said output electrodes and including a circuit element wherein variations of potential drop are produced by said cumulative current changes and means for applying said potential drop to said input circuit to produce said opposite potential changes.

12. A vacuum tube oscillator comprising electron relay means provided with a single output electrode and two control electrodes, an output circuit connected to said output electrode, a tuned input circuit connected between said control electrodes, means for coupling the input circuit to the output circuit for feed-back of oscillating energy, and means for biasing said electrodes to cause said relay to operate within a range for which the output current-control potential curves characteristic of said two control electrodes are oppositely sloped.

13. A vacuum tube oscillator comprising electron relay means provided with a single output electrode and two control electrodes, an output circuit connected to said output electrode, a tuned input circuit connected between said control electrodes, means for coupling the input cirouit to the output circuit for feed-back of oscillating energy, and means including a resistor connecting said input and output circuits to maintain said control electrodes at a bias potential related to the potential of said output electrode such that the output current-control potential curves characteristic of said control electrodes are oppositely sloped.

14. The method of controlling an electric current which comprises generating an electron flow, establishing a pair of oppositely varying potentials differently positioned with respect to said flow, and maintaining each of said potentials within a range of variation wherein said opposite variations have a cumulative effect on the magnitude of said flow.

15. The method of operating a vacuum tube having a cathode, an anode, and a plurality of control electrodes, which comprises the steps of maintaining one of said electrodes at a mean potential whereat a positive variation thereof will produce an increase in electron flow through said tube, maintaining another of said control electrodes at a mean positive potential whereat a positive variation thereof will produce a decrease in said electron flow, and varying the potentials of said control electrodes oppositely and simultaneously to produce a cumulative effect on said flow.

16. A vacuum tube oscillator for producing electrical oscillations having a high degree of frequency stability, said oscillator comprising the combination with at least one vacuum tube having an output electrode and a pair of control electrodes, of means for generating an electron flow in said tube and of means for impressing oppositely varying positive potentials on saidflow to provide variations in the rate of electron flow through the tube.

17. A vacuum tube oscillator comprising a vacuum tube having a cathode, an anode and a pair of control electrodes asymmetrically positioned with respect to said cathode and anode, a resonant circuit connecting said control electrodes, an output circuit coupled to said resonant circuit, and means for imposing a common positive bias on said control electrodes such that opposite changes of potential thereof produce cumulative changes in magnitude of the output current of said tube.

RICHARD E. FURAY.

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