US2248563A - Circuit arrangement for current or potential distortion - Google Patents

Description

Juiy 8, 1941. I

HANNS-HEINZ WQLFF 2.248563 CIRCUIT ARRANG EMENT FOR CURRENT OR POTENTIAL DIST Filed Sept. 28, 1957 ORTION 2 Sheets-Sheet 1 y 3941- HANNS-HEINZ WOLFF 2,248,563

CIRCUIT ARRANGEMENT FOR CURRENT OR POTENTIAL DISTORTION Filed Sept. 28, 1957 2 Sheets-Shegt 2 lye/Walk Patented July 8, 1941 CIRCUIT ARRANGEMENT FOR CURRENT OR POTENTIAL DISTORTION Harms-Heinz Wolfi, Berlin, Germany, assignor, by mesne assignments, to Loewe Radio, Inc., a corporation of New York Application September 28, 1937, Serial No. 166,233 In Germany October 2, 1936 3 Claims.

The present invention relates to circuit arrangement for transmitting television images by means of an electronic tube with a photo-electric storage electrode and is directed to the use of means therein for obtaining a certain current-voltage characteristic. In such television circuit-arrangements for example it is often necessary to obtain a definite characteristic curve in the output circuit, and to dispose this output-potential characteristic with relation to the input potential characteristic, so that the contrast at the light and/or dark parts of the image is increased as compared with the contrast in the range of medium light-intensity values. There are resistances which possess curved characteristics (for example amplifying tubes), and it is also possible to exert a control on these characteristics up to a certain degree (for example by suitable selection of the tube constants, auxiliary grids, biasses and the like). In many cases, however, a certain characteristic is necessary which is not to be obtained in this fashion.

This definite characteristic curve of the mplifying arrangement may be obtained by different means and the present invention suggests such means for attaining special characteristics in such television arrangement with photo-electric storage electrode.

The present invention solves this problem by use of a branched circuit system including at least three branches, the single characteristics of which form together the desired characteristic. According to the invention, in a circuit arrangement, as described above, there is used, for example as coupling means, a branched circuit system including at least three branches and this branched circuit system contains at least two non-linear resistances. As an exemplary embodiment of such a circuit system three resistances of different characteristics may be provided which are so arranged and connected together that the desired distortion of the output current is produced. The single parts are usually situated at different points of the complete characteristic range, and according to the invention they are united by superimposing and suitable shifting (for example by biasses) to form a continuous characteristic and are finally hifted as a whole into the final position by the superimposing of a horizontal characteristic curve.

The invention will be clearly understood from the diagrams and exemplary embodiments shown in the accompanying drawings, in which Fig. 1a and 1b show as an example a desired characteristic curve and the single curves which form together the whole desired characteristic.

Figs. 2 to 4 show exemplary embodiments of the invention.

The basic principles of the invention will be described more concisely in conjunction with Figs. la and 1b. The S-shaped curve I, 2, 3 is a characteristic which is to be obtained. It is pointed out that this S-shaped characteristic is necessary, for example, for increasing the light intensity contrast in the case of television devices with light-storage electrodes (mosaic electrodes). According to the invention, the complete curve l-2-3 is divided into two parts l-2 and 2'-3, which can be found as parts lot-2a and Zia-3b of the characteristics of two different resistances. These parts, however, as shown by Fig. 1a, are disposed in disconnected fashion at difierent points of the complete characteristic range. It is necessary, therefore, by suitable displacement, to join these parts to form a continuous curve. In the assumed instance according to Fig. 1a, which is of a simple nature for the purpose of explanation, it is merely necessary for this purpose to add to the characteristics the two currents i1 and i2, whereby there results the connected curve la,-2a-3d shown in Fig. lb. It will be readily apparent that if the connection of the part-curves is not possible by immediate superposition, this can be accomplished by suitable measures (for example, lateral displacement by an additional anode potential).

In order now to move the curve la,-2a,-3a into the final position l-2-3 merely a displacement is necessary which can be obtained by an additional constant current is, so that the total current i1+i2+i3=i imparts to the current the desired characteristic. The current is may be produced by a resistance connected with a constant potential or in the case of variable potential by the saturation current of a tube.

In Figs. 2 to 4 there will be described certain possible embodiments of the invention in practice.

In Fig. 2 there are combined as resistances within the meaning of the invention three tubes 4, 5 and 6 intended to result in the current curves i1, '22, and is. At the terminals 1 there is supplied the input potential 6a.. The three resistances 4, 5 and 6 are located with a working resistance 8 and a current source l0 and the input potential es in a circuit, so that at the working resistance 8 there occurs the total of the three currents 2'1, 2'2 and is, the value of which in tum is determined by the input potential ea. For the tubes 4 and 5 there are provided current sources l2 and I3 for producing the suitable grid biasses. There are also provided for the tubes 5 and 6 additional current sources 9 and M for producing the necessary anode biasses. Since the current portion is must be negative, as disclosed by Fig. lb, the tube 6 is connected in reverse fashion. Since the tube 6 must be constant in respect of all voltages 6a, the bias l4 and the nature of the tube (for example with tungsten cathode) will be so chosen that it operates in respect of all potentials in the saturation range.

Fig. 3 shows a simplification by omission of the tube 8. This is replaced by a circuit which includes a current source 6a and a preferably adjustable resistance 61) and acts on the working resistance 3. In addition the current sources 9 and ii] are combined to form one current source fi, and the current sources l2 and I3 to form one current source I 2, at which the difierent potentials for the anode potentials and grid biasses for the two tubes can be tapped.

An additional simplification of the arrangement is shown in Fig. 4. The two tubes 4 and 5 are united to form a tube having an anode, a cathode and two grids. be tapped at the terminals ll connected with the working resistance a potential which is distorted as compared with the input potential ea, for example, corresponding to the characteristic 5, 3 (see Fig. la).

The characteristics and connections referred to represent merely examples of the invention and may be modified in numerous ways within he meaning of the invention corresponding to the principles of the invention set forth in the above.

I claim:

1. In a television circuit arrangement the use of coupling means for obtaining a non-linear current-voltage characteristic on a common output resistance for increasing the light-intensitycontrasts of the image, said coupling means comprising a branched circuit system including three branches and an output resistance, two of said branches including separately controlled electron discharge paths, an electronic current In all figures there may modulating control electrode in each of the electronic discharge paths, means for normally biasing the control electrodes at predetermined different potentials, means including a source of potential for causing the electronic current of the two paths to flow through the said common output resistance, the third of said branches including the series combination of an adjustable ohmic resistance and a separate potential source, said series combination being connected in parallel with said common output resistance.

2. A device to be used in a television circuit for obtaining a desired non-linear current-voltage characteristic comprising a common output resistance across which output potentials are dcveloped, said common output resistance being common to three conducting paths, two of said paths each including an electron discharge device having a cathode, a control electrode and an anode, means for applying predetermined different biasing potentials to each of said control electrodes, means including a source of potential and said common output resistance for maintaine ing the anodes positive with respect to said cathodes, a third branch circuit including a series connected additional source of potential and a variable resistance, said series connected additional source of potential and variable resistance being connected in parallel with said common output resistance whereby the potential drop across said common output resistance will be determined by the direction and intensity of the current flow in the three branches.

3. In a television circuit arrangement the use of coupling means for obtaining a non-linear current-voltage characteristic on a common output resistance for increasing the light-intensity-contrasts of the image, said coupling means comprising an electronic valve, including a plate, two grids and a cathode, an adjustable ohmic resistance, grid-biasses and anode-potential sources, and an additional potential source, both said grids of said valve being supplied with different bias-potentials from said sources, said common output resistance being connected in the anode circuit of said valve, said adjustable ohmic resistance serially connected with said additional potential source being connected in parallel with said common output resistance.

HANNS-HEINZ WOLFF.

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