GB232534A - Improvements in and relating to electrical valve amplifiers - Google Patents

Abstract

232,534. Priess, W. H. Nov. 14, 1923. Thermionic amplifiers.-Relates to filament-heating circuits for valve amplifiers using alternating supply current in which a resistance R is connected across the secondary coil of the supply transformer T, and an intermediate tap on this resistance is connected to the grid circuits; and consists in providing condensers K<2>, K<3> across the two sections of the resistance R and in connecting the tap to the grid circuits through a potentiometer H. The filaments of any desired number of valves 1, 2 for amplifying radio or audio frequency currents may be connected in parallel beyond the condensers K<2>, K<3>. Bypass condensers K<1>, K<4> may be connected across the potentiometer H and plate battery b. The Figure shows a two-valve radio-frequency amplifier followed by a detector D and telephones L. The first valve 1 has a tuned grid circuit I, K and transformer couplings A, B between the valves 1, 2 and between the valve 2 and the detector circuit. The potentiometer H may have separate sliding contacts for the several valves, so as to provide separate controls for the grid potentials and consequent damping of the grid circuits, as described in Specification 234,024. A switch may co-operate with tappings on the primary coil of the transformer T for regulating the voltage applied to the filaments; and the core or the secondary coil of this transformer may be earthed. The Specification disclaims the inventions claimed in Specifications 215,455 and 227,189.