GB488695A - Electron discharge apparatus - Google Patents

Abstract

488,695. Valve amplifying circuits. STANDARD TELEPHONES & CABLES, Ltd. Dec. 17, 1937, No. 35046. Convention date, Jan. 6. [Classes 39 (i) and 40 (v)] In order to obtain the condition for high efficiency in Class C amplifiers, that the instantaneous potential of the anode during current flow is considerably less than the constant anode potential, an auxiliary anode is placed between the cathode and anode and suitably connected to the output circuit. The electron discharge device 10, Fig. 1, has an auxiliary anode 20 disposed between the main anode 12 and the control grid 13 and connected to such a point on the inductance 14 of the output circuit that its alternating potential is less than that of the main anode. The auxiliary anode may consist of spaced wires 23 in radial alignment with the grid wires 22, Fig. 3, or may consist of curved strips 25, Fig. 4, in which case a magnetic field produced by the coil 24 is employed to cause the electrons to travel in curved paths. A screen composed of wires in radial alignment with the grid and anode members may be employed. When the grid potential on the positive half-cycle is small, the anode potential E does not fall very much and the alternating potentials appearing on the anodes 12 and 20 respectively are as shown in curves B and A, Fig. 2, the majority of the electrons following the paths P or P<1> and going to the anode 12 which has the lower instantaneous potential and is therefore more efficient. As the input potential increases the instantaneous potential of anode 12 falls and more electrons go to the auxiliary anode along paths such as P<2>, until finally the potentials on the anodes are as shown at A<1>, B<1> anode 12 being negative with respect to the cathode over the greater portion of the half-cycle and the electrons going to anode 20 along paths such as P<3>. In a further embodiment of the idea, Figs. 5 and 6 (not shown), a second auxiliary anode is employed, this anode and the main anode both being negative over the majority of the half-cycle at full load. The invention is stated to be applicable both to high-frequency amplification and to class B push-pull amplification of audio and other frequencies.