US1954782A - Circuit arrangement for thermionic receivers - Google Patents

Description

April 1934- A. ARZMAIER ET AL 1,954,782

CIRCUIT ARRANGEMENT FOR THERMIONIC RECEIVERS Filed Feb. 27, 1929 4 Lawn] Patented Apr. 17, 1934 UNITED STATES PATENT OFFICE CIRCUIT ARRANGEMENT FOR THERMIONIC RECEIVERS Application February 27, 1929, Serial No. 343,154 In Germany January 20, 1928 2 Claims.

This invention relates to electric relay circuits and provides an improved method of supplying energy thereto.

It is known in connection with the operation of apparatus comprising thermionic triodes that, for the purpose of saving the grid battery, the grid biasing potential may be taken off at separate auxiliary resistances in the filament and plate leads. In the case of battery-eliminator sets this would involve the drawback that the direct current potential thus furnished depends upon the load.

The object of this invention is to overcome the above difiiculty. This is attained according to the present invention by the use of a tube circuit arrangement, especially adapted to batteryeliminator sets, in which the grid biasing potential is derived from the direct current resistance of the choke-coils provided for the purpose of smoothing the feed current. The direct current potential obtainable at these choke coils, provided the coils are economically designed, is of the order of magnitude of the requisite grid biasing potential. In order that the grid biasing potential thus furnished may be negative in relation to the filament, it is necessary to include the choke-coils in the negative branch of the filter circuit. It is also recommendable to provide the coils with taps in order that grid biasing potentials of different values may be available.

One embodiment of the idea underlying the invention is illustrated by way of example in the single figure of the drawing. The drawing illus-v trates a two-stage tube amplifier comprising tubes T1 and 12, input transformer t1 and output transformer t2. Filament and plate current is supplied to the set at points and it being immaterial whether a direct current supply network of fluctuating amplitude is connected across the said terminals, or the output circuit of a rectifier connected with an alternating current source.

The smoothing means for the feed current ordinarily consist of two coils d1, d2, which are included in the negative wire, and of condenser 01 and c2 shunted across them. Connected with the said smoothing elements is a resistance 10 arranged potentiometer-fashion, and at the said resistance p are taken off the filament potential and the two plate potentials.

Now, according to the present invention, each of the grids is united with a point or tap of the two choke-coils d1 d2; to be more precise, the grid of tube T1 is associated with coil d2, and the grid of tube T2 with the coil dl. In this manner, the grid of the end or power tube r2 receives a higher negative bias than the grid of tube r1. Inasmuch as at the tapping points, the direct current potential has usually superposed on it fluctuating components means in the grid leads in the form of condensers c3 and 04, respectively, and of resistances wl and w2, respectively, are provided though in lieu of the resistances also choke-coils could be provided for filtering out or by-passing these components. Since inside the range of negative grid potential no current has to be furnished-these smoothing means can be chosen very ample, and this insures a so much greater filtering effect.

The drop of potential at the choke-coils d1 d2 which should approximate the maximum necessary grid biasing potential is dependent on the load of the outfit. Since the latter is not constant, it follows that the direct current potential fall across the choke-coil would vary in an undesirable manner during operation. In order to prevent this action it is of advantage to provide the apparatus with an additional constant load resistance. If the latter is, say, of the order of magnitude of the lowest useful load, then the mean feed current will be about doubled; hence, to insure the same voltage fall across the choke, coils d1 d2 only one-half the ohmic resistance or the output, the furnished direct current potential, especially the drop of potential across the choke-coil, is less dependent upon the useful load of the output, This also dispenses with the necessity of subdividing the resistance value or the choke-coil unduly. The supplementary or auxiliary load resistance may advantageously consist of the potentiometer proper We claim:

1. In a power supply system to be used with amplifying apparatus including a thermionic tube having anode, cathode and control electrodes, a source of pulsating direct current, a current smoothing filter having output terminals, and input terminals connected to said source, a potential divider connected across said output terminals, and a filter impedance connected between one of said input terminals and one of said output terminals, means arranged to provide a connection between said last named output terminal and the cathode of said tube, means comprising a direct current connection between an intermediate portion of said filter impedance and the grid electrode for deriving from the drop across at least a portion of the filter impedance a biasing potential for said control electrode and an alternating current connection between the grid electrode and a point of the circuit between the last named input and output terminals of different potential than the point of the impedance connectedto the grid.

2. In a power supply system to be used with amplifying apparatus including a thermionic tube having anode, cathode and control electrodes, a source of pulsating direct current, a current smoothing filter having output terminals, and input terminals connected to said source, a, potential divider connected across said output terminals and a filter impedance connected between one of said input terminals and one of said output terminals, said filter impedance being in at least two sections, a capacity connected between an intermediate point of said impedance and said other output terminal, means arranged to provide a connection between said cathode and said potential divider whereby a predetermined average potential is applied to the cathode, means arranged to provide a connection between said anode and a point of the potential divider of higher potential than the average potential applied to the cathode, means including at least a portion of said filter impedance for providing a direct current connection between the grid electrode and the cathode of said thermionic device whereby the grid is maintained at a negative potential with respect to the cathode average potential, and means for providing an alternating current path between a point of said potential divider of lower potential than the said cathode average potential than the derived grid potential.

ALFONS ARZMAIER. ANDREAS JAUMANN.

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