US2115881A - Relay circuit - Google Patents

Description

May 3, 1938. H. o. ROOSENSTEIN 2,115,331

RELAY CIRCUIT Filed Feb, 23, 1955 HIGH RES/STfiA/CE name/v7- 0 l l lgl l l l y fa INVENTOR I HANS o. ROOSENSTEIN ATTORNEY Patented May 3, 1938 UNITED STATES RELAY CIRCUIT Hans Otto Roosenstein, Berlin, Germany, assignor to Telefunken GeseHschaft fur D'rahtlose Telegraphic Application February 23, 1935, Serial No. 7,923 In Germany February 17, 1934 3 Claims.

The present invention relates to a circuit for varying the course of the amplitude, and more particularly for limiting amplitudes of any shape.

For the limitation of amplitudes and for the 5 variation of the curve shape of voltages variable in time, the saturation properties of electron tubes having tungsten cathodes have often been utilized. In modern tubes with activated cathodes (oxide cathodes) however, the saturation is not prominent i. e. in the ordinary operation it must not be attained in view of a minimum of life to be required. Modern tubes therefore cannot be utilized in a practical manner for the purpose of amplitude limitation by way of varying the curve shapes.

In accordance with the present invention, it is possible to use tubes which do not possess pronounced saturation properties for amplitude limitation purposes.

In accordance with the present invention the voltage tobe limited is not directly applied to the tube between the grid and the cathode, but is impressed upon the grid across a very high resistor, eventually with the series connection of a biasing voltage.

The limited voltage or the limited current may be taken from a point between a third electrode' (anode) and the cathode, in which case an aperiodic resistor is to be used as load, in order to retain the flattened curve shape produced in the grid circuit. The limited voltage or the limited current also may be directly tapped between grid and cathode if the connected apparatus has a sufiiciently high resistance. In the last case a diode may be used without danger.

This method is not limited to a special type of cathode, and if desired may also be applied with advantage to pure tungsten cathodes.

The proposed circuit preferably serves for the limitation or flattening out of undulated direct voltages, for instance, for the reception of written messages, for the anti-fading in receiver circuits, and for the modification of the curve shape of alternating voltages. By applying sufiiciently large amplitudes the method may also be used for the production of impulses of trapezoidal and rectangular shape.

An example of a circuit which may be used for carrying out the inventive idea is diagrammatically illustrated in the single figure of the drawmg.

In the drawing, the discharge tube V is a triode having a cathode k, a grid 9 and an anode a. In front of the grid, namely between the terminal A and the grid 9, there is placed a high resistor R.

If required a bias source Ev is inserted. The voltage U1 to be limited is applied across the terminals A and B. The limited voltage can be tapped between the terminals P and Q (Ua) or directly between g and R: (Ug) that is, by connection of the load across terminals P Q.

In the present application use is made of the fact that at slightly negative or slightly positive grid with respect to the cathode, the grid current begins to flow which is in practice exclusively produced by the normal electron current. This current increases with extreme rapidity in the Maxwells portion of the characteristic and in accordance with an exponential function. Approximately up to the value I =10 A, the current increases e times for each 0.1 volt increase of the grid potential, e being equal to 2.718, .(see Barkhausen, Elektronen Roehren vol. 2, 1933, pages 281-283).

In view of the fact that there is connected in the grid lead a resistor R which is high as compared with the inner resistance of the discharge path, cathode-grid g and as compared with the' other resistors in the grid circuit, the amperage in this circuit is practically determined only by the resistor R. Hence for instance at a voltage variation between the terminals A and B in the range from 1 to 1000 volts, the amperage. will likewise change to 1000 times its original value. minal A is hereby considered positive. To increase the grid current 1000 times, an increase of the grid potential by only about 0.7 volt is required. It will be seen therefrom that a voltage change between A and B of for instance from 1 to 1000 volts causes at the grid g a voltage change of only 0.70 volt, i. e. an extremely effective limitation of the grid voltage will be obtained if the terminal A is positive. If however the terminal A is highly negative no grid current flows as is known.

According to Barkhausen, Elektronen Roehren v01. 2, 1933, page 281, the exponential increase of the grid current reaches only up to approximately a value Ig=10 However it was found in the latest indirectly heated types of tubes that an exponential increase or an increase similar to an exponential course can be shown up to currents of 10- A. This region can likewise be utilized with the same advantage in the sense of the present invention for the purpose of limiting or modifying amplitudes. In many cases therefore the use of indirectly heated tubes is to be recommended.

In order to avoid plate reactions especially in the case of very high frequencies it appears to be advisable to use screen grid tubes.

The ter- If the desired form as for instance rectangular shape of the amplitude cannot be obtained by means of a single tube, it is advisable to carry out the flattening to the desired shape in an identical manner in a cascade circuit.

I claim:

1. An electrical relay circuit including a thermionic tube having an anode, a cathode and a grid electrode, means for energizing the cathode, means for establishing a flow of space current between the anode and cathode and means for applying a positive potential on the grid electrode with respect to the cathode, an input circuit for the tube connected between the grid electrode and the cathode and including in series the last named means, a pair of input terminals and a resistor element, said resistor element having a resistance value which is high as compared to the internal resistance of the tube measured across the grid electrode and the cathode and an output circuit connected directly across the grid electrode and the cathode.

2. In a circuit arrangementfor changing the course of electrical oscillations by limiting the amplitude thereof, a thermionic tube having a cathode, a first cold electrode and a second cold electrode, means for energizing the cathode, means for maintaining both of the cold electrodes at a positive potential with respect to the cathode, an input circuit for the tube connected between one of the cold electrodes and the cathode thereof, and including a resistor element and a pair of input terminals in series, said terminals serving as a means for connection of the source of elec- "trical oscillations to be limited, said resistor ele- HANS OTTO ROOSENSTEIN.

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