US2496361A

US2496361A - Cathode-ray deflection type amplifier

Info

Publication number: US2496361A
Application number: US696792A
Authority: US
Inventors: George C Sziklai
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1946-09-13
Filing date: 1946-09-13
Publication date: 1950-02-07
Anticipated expiration: 1967-02-07

Description

F b; 7, 1950 s. c. SZlKLAl 2,495,361

CATHODE-RAY DEFLECTION TYPE AMPLIFIER Filed Sept. 13, 1946 Isnveutor fiiawi C SZ/ A/ Patented Feb. 7, 1950 :CA'THODE-RAY DEFLECTION TYPE AMPLIFIER George C. Sziklai, Princeton, N. 3., assignor to Radio Corporation-of zfimerica, a corporation of Delaware Application September 13, 1 9 46 Serial ivefcsu snsz 3 Claims. (01.311540) This invention relates to cathode ray tubes and I to the utilization of such tubes as amplifiers,

In amplifiers of the triode type amplification is limited as a practical matter tothe value at which the tube breaks into oscillations. This is due to the feeding back of energy from the output to the input circuit in resonance with the alternating energy applied to the input circuit.

It is an object of this invention to provide an amplifier tube in which there is substantially no tendency to operate as an oscillator.

Another object of the invention is to provide a cathode ray tube that will readily and efiiciently amplify signals.

Another object of the invention is to provide an amplifying tube of inherent high gain and low terminal capacities at a wide range of frequencies.

Other objects will appear in the following description reference being had to the drawing in which:

Fig. 1 is a diagrammatic illustration of a cathode ray tube embodying the invention; and

Fig. 2 is an enlarged end View of the gun of the tube.

Referring to the drawings the tube embodying the invention comprises an evacuated envelope I having a gun G adapted to form a ribbon-like beam B. This may comprise a linear cathode 2 having a heater I-I (Fig. 2), a cylindrical grid 3 with a slit aperture and a first anode 4 having a similar slit aperture. At the other end of the tube. is located the target T, comprising a conducting plate having a surface 6 of conductin material capable of strongly emitting secondary electrons under bombardment of primary electrons and a surface I, that is substantially nonemissive or emits secondary electrons at a low rate as compared to that in surface 6. The surface I may be a triangle, base down, lying between triangular surfaces 6, base up. The surfaces 6 may, for example, be composed of caesium silver or silver magnesium and the surface I may be carbon or carbonized material.

A pair of electrostatic deflection plates 8 and 9, or equivalent magnetic means, are connected to terminals Ill and I I on which the signals S are to be impressed. The terminal I I is connected to the cathode and may be grounded at G. A mesh screen or equivalent electrode I2 is placed between the gun and the deflector plates. This screen may be connected to ground through a resistor I3 and a source of voltage M to apply a potential either positive or negative to the screen. The screen I2 is also connected to the target through a resistor I5.

I A second mesh screen or equivalent output anode I6 is positioned in front of the target T and is connected to ground through a resistor I1 and source of voltage I8, which places a potential onthe screen sufficiently positive, relative to that of the cathode, to accelerate the beam and cause it to bombard secondary electrons from the target surface 5 in greater than unity ratio while electrons are bombarded from surface I at considerably less than unity ratio.

The method of operation of the tube as an amplifier of signals may be described as follows:

The ribbon-like beam B from the gun, with no signals on leads I0 and I I, is accelerated by screen anode i6 and lands partly on the surface 6 and partly on surface I as indicated by line I9. The secondary electrons emitted are collected by this screen and the surface 6 goes positive but surface I goes negative. The net potential of these surfaces raises or lowers the potential of screen I2 and this varies the intensity of the ribbon beam B in known way. More or less secondary electrons, as the case may be, are bombarded from the surface 6 and the beam intensity is further varied. When signal energy is applied to the plates 8 and Q the beam is deflected up and down the target in proportion to the signal strength. When this beam is deflected upwards in Fig. 1 the linear landing area IS on surface 6 increases and that on surface 1 decreases. This varies the secondary emission and raises the potential of target T, which increases the intensity of the beam by increasing the potential of screen I2. When the signal decreases the beam is deflected downwards (as shown in Fig. 1) which decreases the linear landing area on surface 6 and increases it on surface .I. This decreases the secondary emission and the potential of the target. Thus, the intensity of the beam is decreased, and the swings of the signal are amplified to a great extent. The amplified signals of the output electrode I6 may be applied to an amplifier typified by tube 29 through a coupling condenser 2I and load resistance 22.

In my improved cathode ray amplifier the apparent mutual conductance of the tube may be made very high with comparatively wide electrode spacing resulting in low terminal capacities. This provides high gain at a wide range of frequencies with no tendency to oscillate at such high gain. The high apparent mutual conductance and low terminal capacities make the tube particularly useful as a high gain wide band amplifier.

While certain specific embodiments have been illustrated and described, it will be understood 3 that various changes and modifications may be made therein Without departing from the spirit and scope of the invention.

What I claim as new is:

1. A cathode ray tube system comprising, an envelope containing a gun adapted to produce a flat electron beam, means for deflecting the beam perpendicularly to its flat sides in proportion to received signals, a target having scanning lines of successively increasing length transverse to the direction of the beam deflection, an anode for collecting secondary electrons emitted by said target, and a screen mesh in the path of the beam and a circuit connecting said screen and said target for superimposing the variations of the potential of the target on the potential of the screen.

2. A cathode ray tube system comprising, an envelope containing a gun adapted to produce a flat electron beam, means for deflecting the beam perpendicularly to its flat sides in pro-portion to received signals, a target having scanning lines of successively increasing length transverse to the direction of the beam deflection, an output anode for collecting secondary electrons emitted by said target, a screen mesh in the path of the beam between the gun and said means and a circuit connecting said screen and said target for 4 superimposing the variations of the potential of the target on the potential of the screen.

3. A cathode ray tube system comprising, an envelope containing a gun adapted to produce a flat electron beam, means for deflecting the beam perpendicularly to its sides in proportion to received signals, a target comprising a triangular area having good secondary electron emissivity on'which said beam is adapted to impinge, a screen mesh output anode in front of the target for collecting secondary electrons emitted under impact of the beam on the target, a second screen mesh in the path of the beam in front of the deflecting means and a circuit connecting the second screen mesh and the target for superimposing the variations of the potential of the target on the potential of said second screen mesh.

GEORGE C. SZIKLAI.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,257,795 Gray Oct. 7, 1941 2,458,539 Seller Jan. 11, 1949