US2092881A

US2092881A - Electron discharge device

Info

Publication number: US2092881A
Application number: US678040A
Authority: US
Inventors: Jonker Johan Lodewijk Hendrik; Albricht Wilhelm
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1930-06-21
Filing date: 1933-06-28
Publication date: 1937-09-14
Anticipated expiration: 1954-09-14
Also published as: BE380459A; NL34771C; GB369480A; DE563558C

Description

Sept. 14, 1937. J. L. H. JONKER iz-r AL ELECTRON DI S CHARGE DEVI CE Original Filed June 22, 1931 INVENTOR JOHAN L.H.JONKEPs WIVEggBPHGHT BY Mlrf l ATTORNEY Patented Sept. 14, 1937 UNITED STATES ELECTRON DISCHARGE DEVICE Johan Lodewijk Hendrik Jonker, Eindhoven, and

Wilhelm Albricht, The Hague, Netherlands, assignors to Radio Corporation of America, a corporation of Delaware Original application June 22, 1931, Serial No. 545,946. Divided and this application June 28, 1933, Serial No. 678,040. In the Netherlands June 21, 1930 5 Claims.

This application is a division of application S. N. 545,946 entitled Amplifying circuit arrangement with parallel supply filed June 22nd 1931 and issued as Patent No. 1,957,542.

With this kind of circuit the direct current is commonly supplied to the anode through a choke coil opposing a very high impedance to all the frequencies to be amplified. In parallel with the direct-current circuit is connected an alternating current circuit which is blocked for direct current by means of a condenser.

In order to obtain the greatest possible amplification with a circuit-arrangement of the kind above referred to, the impedance of the choke coil for all the frequencies to be amplified must practically be infinitely high. This condition can hardly be fulfilled and it has therefore been proposed to connect a saturated diode instead of the choke coil. Beside a comparatively low directcurrent resistance such a diode has a very high alternating current resistance which moreover is independent of the frequency. On superficial consideration the saturated diode seems to be therefore a coupling element having very favorable properties. In practice it appears however that the use of a diode does not lead to the desired result and that it is impossible to amplify a broad range of frequencies.

The invention is based on the View that the unsatisfactory working of this circuit-arrangement is due to the fact that with the use of a saturated diode the filament is connected to abattery or other source of current, owing to which the filament obtains a comparatively large capacity with respect to earth. Since on the other hand the filament of the amplifier valve has also an appreciable capacity relatively to earth, the

diode acting as a coupling element is shunted by a rather large capacity. The coupling element consequently has not a very high alternating current resistance for comparatively high fre quencies.

According to the invention, in order to eliminate this drawback use is made of a diode with an indirectly heated cathode.

With a diode comprising an indirectly heated cathode the capacity of the latter relatively to earth can be kept very small and need in general not be larger than the capacity between the grid and the cathode of the valve with which the first valve is coupled.

According to the invention, in order to avoid that the capacity of the cathode due to the close proximity of the heating element with the electric circuits connected thereto obtains notwithcurrent circuit 6 of the repeater tube 1.

standing a considerable value, the heating element may be arranged in such a manner that the electrostatic capacity between the cathode and the heating element is very small. For example, the heating coil may be arranged at the exterior around the anode so that the supply of heat to the cathode takes place across the anode. Besides, according to the invention, use is preferably made of a. cathode which is very thin. This affords the advantage that the electric field strength perpendicular to the cathode may obtain a high value and this high Value of the field strength causes again that the alternating current resistance of the whole diode is altered.

In fact, the alternating current impedance of the saturated diode which at first seems to be infinitely high, depends in reality on the absolute temperature and on the electric field strength at the surface of the cathode.

The general character of the expression of the alternating current resistance is thus:

In this expression a denotes a constant, T the absolute temperature and F the field strength perpendicular to the cathode surface. When use is made of a heating coil, surrounding the anode,

heating of the latter is of course unavoidable but a heated anode has no harmful effect on the working of the diode, even not if the temperature is so high that the anode begins to emit, for after being emitted the electrons immediately attain an electrostatic field which drives them back to the anode.

The invention is disclosed in the accompanying drawing in which Figs. 1 and 2 represent diagrammatically an approved form of the apparatus and a modification thereof.

In Fig. 1 the diode 5 is connected in the direct The diode comprises a fine wire cathode 8, an anode 9 surrounding the cathode and a heater coil l0 wound around the exterior of the anode. The anode or B battery II is connected to the anode 9 of the diode 5. The. direct currentcircuit for the device I is from the positive side of the battery H to anode 9, cathode 8, through circuit 6 to the anode of device I through ground to the negative side of battery H.

In the modification illustrated in Fig. 2, the cathode 8 is surrounded by a heater element I2 which comprises the anode of the device. Otherwise the circuit of Fig. 2 is the same as the circuit of Fig. 1.

The invention is applicable to high frequency as well as low frequency amplifier circuit arrangements of any kind, quite independently of the purpose for which the apparatus having such a circuit-arrangement is utilized. The invention may also'be applied in order to couple the anode circuit of a detector valve with the succeeding low frequency amplifier or with a telephone or other indicator.

What we claim is:

1. An electron discharge device comprising a cylindrical anode, a cathode extending within the anode, and means disposed externally of the anode and supported thereby for heating said cathode, said heating means being in the form of a bifilar winding adapted to be energized from an alternating current source.

2. An electron discharge device comprising a cylindrical anode, a cathode extending within the anode, and means supported from the outer surface of the anode for heating said cathode solely by heat radiation, said heating means being in the form of helically-wound parallel wires adapted to be energized from an alternating current source.

'lindrical tubular anode closed at one end, a cathode extending within the anode from the opposite end and coaxially disposed therein, and means carried by the outer surface of the anode for heating said cathode solely by heat radiation.

5. An electron discharge device comprising a cylindrical tubular anode closed at one end, a cathode extending within the anode from the opposite end and coaxially disposed therein, and means carried by the outer surface of the anode for heating said cathode solely by heat radiation, said heating means being in the form of a pair of. parallel wires helically-wound and adapted to be energized from an alternating current source.

JOHAN LODEWIJK HENDRIK JONKER.

WILHELM ALBRICHT.