GB635132A - Improvements in and relating to thermionic valve amplifiers - Google Patents

Abstract

635,132. Valve amplifying circuits. GENERAL ELECTRIC CO., Ltd., and ESPLEY, D. C. Jan. 8, 1947, No. 654. [Class 40 (vi)] In an amplifier in which separate D.C. paths are provided for the anode currents of two amplifying valves connected for operation in parallel, protective means are provided responsive to a change exceeding a predetermined amount in the difference between the anode currents in the valves. As shown, an amplifying stage comprises two valves 10 having the cathodes and grids connected together respectively and the anodes connected through separate impedance elements 19 and separate windings 20 of a relay 21 to H.T. positive. The relay is actuated when the currents in its windings, which are in opposition, become unequal and it then actuates switch 27 to give an indication of failure or perform any desired change of connections. Each anode is connected through a separate capacitor 24 to the output terminal, or alternatively as in Fig. 2 (not shown), the capacitor may consist of two sets of plates connected to the respective anodes co-operating with a single plate connected to the output terminal, and the two anode impedances may be constituted by a bifilarwound choke. With four valves in parallel, Fig. 3 (not shown), each pair of valves is connected through a double-wound relay as in Fig. 1, both pairs being then connected through a further double-wound relay to H.T. positive.