GB191038A - Improvements in and relating to electric current amplifiers - Google Patents

Abstract

191,038. British Thomson - - Houston Co., Ltd., (Assignees of Hull, A. W.). Dec. 28, 1921, [Convention date]. Vacuum tubes.- A four-electrode thermionic valve comprises the usual cathode, grid and anode and a slat electrode interposed between the grid and anode, adapted to receive electrons from the cathode and to emit impact or secondary electrons which are attracted to the more positive anode. The input potentials are impressed on the grid circuit, and the amplified output current flows through an indicator in the anode circuit. Fig. 1 shows the circuit, and Fig. 3 is a cross section, of one form of valve. The slat electrode 3 interposed between the grid 2 and anode 4 comprises a number of slats 6 spaced apart and lying in radial planes, as described in Specification 180,655. The circuit between the slat electrode 3 and the filament, includes an adjustable portion of the anode battery 9. The ancde circuit also includes a telephone 11 or other indicator. The electron stream is caused to travel in a curved path by providing a steady axial magnetic field within the valve by means of an external coil, which may be independently energized, or may be connected, as shown at 12, in the anode circuit, the variable component of the anode current being shunted from the coil 12 by a condenser 13. The electrons strike the sides of the slats 6 and by their impact liberate secondary electrons which pass to the anode 4. In a modification the axial magnetic field is not employed, but the slats are placed at an angle to the radial plane, so as to intercept the radially-moving electrons. The circuit of the slat electrode has a negative resistance, which may be balanced by a series positive resistance, as in Specification 15555/15. Specification 188,707 is also referred to.