GB462027A - Improvements in and relating to electric discharge devices - Google Patents

Abstract

462,027. Discharge apparatus; thermionic valve circuits. BRITISH THOMSON-HOUSTON CO., Ltd. Aug. 26, 1935, Nos. 23873, 23874, and 23875. Convention dates, Aug. 24, 1934, Aug. 25, 1934, and Aug. 25, 1934. Drawings to Specification. [Classes 39 (i) and 40 (v)] An electric discharge device has within its envelope a " negative resistance, connected either in parallel with the discharge path, or in series with the cathode lead. A " negative " resistance is one which, by virtue of a negative temperature coefficient of resistance, carries a voltage independent of the current passing through it over a certain range. The parallel connected resistance serves to maintain the anode voltage constant in spite of variations of supply voltage, which are taken up by a series ohmic resistance. The resistance in the cathode lead supplies grid bias which is independent of variations of the anode current. Both resistances may be used simultaneously in the same device. The grid bias resistor may include an ohmic resistance which may also form part of the resistance connected in series with the negative resistance in parallel with the discharge path. The resistance materials are preferably electron-conductive metal oxides such as those of uranium, chromium, cobalt and manganese, formed into rods. To enable the negative resistances to work at the correct temperature they may be heated by placing them in reflectors collecting heat from the hot electrodes of the discharge device or by coating them with white aluminium oxide, barium sulphate or magnesium oxide ; or they may be cooled by screens protecting them from hot electrodes or by coating them with black carbon dust. High resistances may be provided with a core of refractory material such as thorium, magnesium or aluminium oxides, to increase their mechanical strength. Other ohmic circuit resistances may be mounted in the envelope.