US1943459A - Thermionic valve circuits - Google Patents

Description

Jan. 16, 1934. J ROUND r AL 1,943,459

THERMIONIC VALVE CIRCUITS Filed Feb. 2, 1924 BALANCING ...L. CAPACITY R2 ,HlGH RESISTANCE 0F EQUAL VALUE Snuentoz HENRY JOSEPH ROUND AND PETER W. WILL/W5.

Patented Jan. 16, 1934 UNETE STATES ATENT OFFICE Willans, Towcester,

England,

assignors to Radio Corporation oi America, a corporation of Delaware Application February 2, 1924, Serial No. 690,220, and in Great Britain February 5, 1923 6 Claims.

When a circuit is connected to the grid and filament of a three electrode valve and another circuit is connected to the anode and filament, there is a possibility that the system may start oscillating for example owing to the fact that the capacity between the anode and the grid furnishes an electrostatic coupling between these two circuits. This is particularly true if instead of a single valve several valves are arranged in cascade.

U. S. Patent 1,334,118 to C. W. Rice shows how oscillation may be prevented by dividing the inductance of the grid circuit into two portions by the lead from the filament instead of connecting I the filament to the end of the inductance as is usual, and by connecting a balancing capacity between the anode and grid circuits.

According to this invention and with a view to preventing oscillation of a valve we divide either the condenser of one or" the circuits or else the inductance of the anode circuit into two portions by the lead from the filament and we connect a balancing capacity between the two circuits. According to this invention also we may employ as the balancing capacity an unlit in a condenser of a difierent type.

In cases of cascade valve systems this anticoupling device can be employed between each valve and the next, or in certain cases, here and there along the valve system. Thus greater magnification can be employed than was formerly possible.

Our invention is illustrated by the accompanying drawing in which Figs. 1 and 2 are diagrammatic representations of different modifications embodying the invention.

Fig. 1 shows an aerial circuit A connected to the grid G and filament F of a valve whose plate or anode P is connected to an oscillatory circuit 0 the capacity of which is divided into two portions C C1 by the lead from the filament. K is a burnt-out valve similar to the acting valve and inserted as a balancing capacity between the circuit 0 and the grid.

If the plate voltage changes current will flow across the condenser formed by the plate P and grid G of the valve through the coil A thereby impressing an undesirable voltage across the grid filament circuit of the valve which will have the effect of disturbing the incoming signals and it may even mask them together. This disturbing voltage is compensated for by the condenser formed of the plate and grid of the valve K which is connected between the grid of the main valve and the lower end of the net work comprising the coil 0 and the condensers C and C1. Owing to the symmetrical arrangement of this net work the plate current of the valve will cause currents in phase opposition to fiow through the condensers C and Cl and sufiicient current will be diverted from the condenser C1 by the unenergized valve K to exactly balance the disturbing voltage resulting from the condenser action of the plate P and grid (3-. This current will, of course, have the correct phase relationship on account of the symmetrical arrangement of the circuits and consequently any disturbances resulting from the action of the plate P and grid G as a condenser will be neutralized.

Fig. 2 shows an arrangement in which oscillation is prevented by connecting the filament to a point near the middle of the inductance of circuit 0.

In this case a changing plate voltage will cause current flow across the condenser formed by the plate P and grid G through the coil A and an equal and opposite current will flow through the coil A due to the presence of the condenser formed by the plate and grid of the valve K connected as shown by the divided impedance 0.

In Fig. 3 the arrangement is similar to that in Fig. 1 except that the divided condenser in this case is placed in the grid circuit instead of the plate circuit and two equal resistances R1 and R2 are shunted across the parts of the diided condenser to assist in the neutralizing action.

Having described our invention what we claim 1. The combination with a three electrode valve of a circuit connected to the anode and containing two condensers, a connection from the filament to a point between the said condensers, a circuit connected to the grid and a pacity inserted between the two circuits to balance the capacity between the grid and anode of the valve.

2. The combination with a three electrode Valve of a divided capacity having a lead connected from the midpoint thereof to the cathode and an end connected to one of the other electrodes and a balancing capacity connected between the other electrode and the other end of the capacity said balancing capacity having a value substantially equal to the capacity between said other electrodes of the valve.

3. The combination with a three-electrode valve of a capacity in the anode circuit of the valve divided into two parts and having a lead connected from its mid-point to the cathode and an end connected to the anode and a balancing capacity connected between the grid and the other end of the capacity.

4. The combination with a space discharge device having an anode, a cathode and at least one grid electrode, a circuit including three capacities in series connected between the anode and the grid electrode, a connection from the cathode to a point between two of said capacities, one of said three capacities being formed so as to be equal to the capacity between the grid elec trode and anode of the space discharge device.

5. The combination with a space discharge device having an anode, a cathode and grid electrode, of a capacity in the anode circuit thereof divided into two parts and having a lead connected from a point intermediate said two parts to the cathode and an end connected to the anode, a balancing capacity connected between the grid electrode and the other end of the capacity, said balancing capacity comprising the capacity existing between the anode and grid electrode of a space discharge device similar to the first named space discharge device.

6. The combination with a space discharge device having an anode, a cathode and at least one grid electrode, a divided capacity arranged so that a portion thereof is connected in the grid cathode circuit of said space discharge device while another portion thereof is connected in the anode, cathode circuit thereof, separate resistances shuntedacross the respective portions of the divided capacity, a coil shunted across the entire divided capacity, said coil having one end connected to the grid electrode and the other end connected to the anode electrode, said last connection capacity.

HENRY JOSEPH ROUND. PETER WILLIAM WILLANS.

including a balancing

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