GB381233A - Improvements in or relating to thermionic valve circuit arrangements - Google Patents

Abstract

381,233. Valve circuits. ELECTRICAL RESEARCH PRODUCTS, Inc., 195, Broadway, New York, U.S.A.-(Assignees of McNally, J. O. ; 48, Mountain Avenue, Maplewood, New Jersey, U.S.A.) July 3, 1931, No. 19269. Convention date, July 9, 1930. [Class 40 (v).] In order to compensate for imperfect matching in the characteristics of push-pull valves and to prevent damage to one valve in case of failure of the other, grid-biasing resistances are provided in the anode-cathode circuit of each individual valve. The push-pull valves 3, 3<1> have their filaments heated by alternating current from separate secondaries 8, 8<1> of the power transformer. The common portion of the two grid circuits includes a resistance 7, which with condensers 12, 12<1> forms a filter to eliminate ripple in the separate grid-biasing resistances 9, 9<1> connected between the high tension negative terminal 13 and the individual centre points of the windings 8, 8<1>. Resistance 7 is large compared with 9 or 9<1> and the filter prevents hum or noise components of the space current reaching the grids. Where indirectly heated valves are employed, the filaments are supplied from a single winding and the resistances are connected between the cathodes and high tension negative, Fig. 2 (not shown). The invention is applicable either to amplifiers or oscillators.