GB536229A - Improvements in or relating to grounded plate amplifiers - Google Patents

Abstract

536,229. Valve amplifying circuits. MARCONI'S WIRELESS TELEGRAPH CO., Ltd. Oct. 31, 1939, No. 29093. Convention date, Nov. 15, 1938. [Class 40 (v)] .A push-pull valve amplifying circuit especially for high frequencies comprises two triodes 5, 7, Fig. 1, with the anodes 9, 11 grounded by a condenser 13 and supplied with voltage from a battery 15, the grids connected to inductors 23, 25 fed from the secondary of a transformer having a midpoint supplied with bias voltage by a battery 43, the cathodes connected to an inductor -in two sections 17, 19 grounded at the mid point 21, and the cathodes also connected by condensers 47, 49 to inductors 51, 53 connected at their other ends to the inner ends of the inductors 25, 23 to prevent self oscillations. In the preferred construction, the coupled inductors are in the form of linear conductors, the inductors 17, 19 being parallel tubes tuned to a quarter wave length by capacitance or by a connection adjustable lengthwise, and the other inductors being within the tubes. The whole is enclosed in a shield. In a modification, Fig. 3, the cathodes are directly heated and this necessitates two pairs of parallel tubes 57, 59 and 61, 63 arranged with the valves 5, 7 and the other devices in the shielding casing 29.