US2058738A - Electrical circuit for cold cathode tubes - Google Patents

Description

' Oct. 27, 1936. H. sT. LAURENT, 2,058,738

ELECTRICAL CIRCUIT FOR COLD CATHODE TUBES Original Filed Oct. 23, 1953 INVENTOR HERBERT ST. LAURENT TORNEYS Patented Oct. 27, 1936 ELECTRICAL CIRCUIT FOR COLD OATHODE TUBES Herbert St. Laurent, Hastings-on-Hudson, N. Y., assignor to Radio Research Laboratories, Inc., New York, N. Y., a corporation of Delaware Application October 23, 1933, Serial No. 694,740 Renewed April 20, 1936 4 Claims.

This invention relates to an electrical circuit for use with a cold cathode, or gaseous discharge, device such as those disclosed for example, in copending applications Serial No. 519,498, filed 5 March 2, 1931 andNo. 548,410 filed July 2, 1931 by John A. Heany and Philip M. Haficke. Those applications disclose a tube in which there is an appreciable content of gas and in which an electron discharge occurs between electrodes which are not heated. As disclosed in those applications these electrodes, which are all within the envelope, may comprise a cathode, cathanode, control electrode and anode. The electrodes may be arranged concentrically in the order named and (1) the internal electrode may be the cathode while the external electrode is the anode; or (2) they may be arranged oppositely so that the internal electrode is the anode and the external electrode is the cathode. A tube arranged in accordance with (1) above is called herein an internal cathode tube, while a tube arranged in accordance with (2) above is called an external cathode tube.

The electrodes may also be plain and arranged parallel to one another along a common axis,

as disclosed for example in my copending application Serial No. 605,189, filed April 14, 1932.

This invention has particular reference to tubes in which the external electrode is used as the cathode. This type of tube has usually proved to be much more sensitive to weak signals than tubes of the internal cathode type. This is prob ably due to the fact that the larger cathode surface of the external cathode type of tube generates more electrons and consequently increases the mutual or trans-conductance of the tube. These tubes, however, have presented difiiculties in use due to the fact that they are frequently unstable. When they have been connected in a circuit of a radio receiver, for example, and the circuit adjusted for maximum sensitivity, they tend to oscillate with any change of the temperature of the gas within the tube, which of course causes a change of pressure, or when the circuit is tuned to a different frequency. It is possible to use such a tube with my new circuit in a radio receiver or other electrical circuit in any manner in which an ordinary vacuum tube may be used, and due to the improved characteristics of such 5 a tube over vacuum tubes, to obtain much better results.

In the drawing,

Fig. 1 is abroken away View of an. external cathode tube which may be used with the circuit 5 of my invention; and

Fig. 2 shows a circuit diagram of the invention.

In the drawing there is shown a gaseous discharge device I, in which there is a cathode 2,

a cathanode 3, a control electrode i, and an anode 5. As previously stated, this inventionis 5 particularly adapted for use with tubes in which the electrodes are arranged concentrically and the cathode 2 is the external electrode, as shown in Fig. 1. It may, however, be used with the other types of arrangement disclosed in the afore- 10 mentioned copending applications. An antenna 6 is connected to ground through a primary coil 1. A secondary coil 8 is connected on one side to the control electrode 4, and on the other side through a variable resistance 9 to the cathanode 15 3. A variable condenser Ill is connected in series with a condenser H across the secondary 8, and may be adjusted to tune this circuit to a received radio Wave. A battery indicated by plus and minus signs has its positive pole connected to the anode 5 through a resistance 12. The output of the tube is taken off across this resistance through a condenser IS. The negative pole of the battery is connected through a resistance I4 to the cathode 2, and through a resistance 15 to the cathanode 3. It will be noted that this pole is also connected through resistance l5, variable resistance 9 and coil 8 to the control electrode 4.

If the resistance 9 is short circuited and the circuit 8|0 tuned to a received radio wave, there will, as before stated, be a tendency for the circuit to oscillate. If the variable resistance 9 is adjusted so that its resistance increases, however, this tendency is eliminated and the tube and circuit operate with highly satisfactory results.

Although I have been unable to form any theory of the operation of this circuit which fully satisfies me, it is my belief that the following explanation is correct. An incoming signal is im- 40 pressed on the control grid 4, the frequency being selected by coil 8 and condenser Ill. The control grid 4 and the cathanode 3 being in the negative glow of the cathode 2, the current from anode 5 tends to shiftt-o the electrode having the 45 higher potential. With resistor 9 short circuited electrodes 3 and 4 have approximately the same D. C. potential and the anode current is consequently fed back to the input circuit in phase with the impressed oscillations through whichever 5 electrode is at a higher potential due to these impressed oscillations. When the resistance of the Variable resistance 9 is increased, however, this causes the electrode 4 to be at a difierent potential than that of the electrode 3, and new tralizes the tendency to feed back into the control circuit. This potential difference need be only slightly larger than the signal input voltages.

Whatever may be the true explanation of the operation of this circuit, however, the circuit itself operates very satisfactorily as an amplifier, detector, or modulator in a radio circuit.

What is claimed is:

1. A gaseous discharge device of the external cathode type having an envelope, a cathode, cathanode, control grid, and anode within said envelope, an input circuit connected across said control grid and cathanode, an output circuit connected across said anode and cathode and coupled to said input circuit to produce an inherent tendency to regeneration, and means comprising a variable resistance connected in said input circuit for preventing regeneration of said circuit.

2. A gaseous discharge device of the external cathode type having an envelope enclosing the electrodes, an electrical circuit comprising an input circuit and an output circuit coupled to said input circuit so that there is an inherent tendency to regenerate, and means for preventing regeneration in said device and circuits, said means comprising a variable resistance in said input circuit.

3. A gaseous discharge device of the external cathode type having an envelope, a cathode, a cathanode, a control grid, and an anode within said envelope, an input circuit for said device, an output circuit for said device coupled to said input circuit to produce an inherent tendency to regenerate, and means connected in said input circuit for controlling regeneration in said device and circuits.

4. A gaseous discharge device comprising a cathode, cathanode, control grid and anode, a source of potential, a resistance connected between the positive pole of said source and said anode, an output circuit connected across said resistance, a second resistance connected between the negative pole of said source and said cathode, a third resistance connected between the negative terminal of said source and said cathanode, and a variable fourth resistance connected between said third resistance and said control grid.

HERBERT Sr. LAURENT.

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