GB391489A - Improvements in or relating to thermionic amplifiers - Google Patents

Abstract

391,489. Valve amplifying circuits. MARCONI S WIRELESS TELEGRAPH CO., Ltd., Marconi House, Strand, London, and GREEN, E., Penrose, Long Stomps, Chelmsford, Essex. Oct. 29, 1931, No. 30036. [Class 40 (v).] The input electrodes of a plurality of valves V1<111> .. V4<111> in a single stage of amplification are so connected to the preceding stage that the input alternating voltage applied to the individual valves is adjusted to suit the characteristics of the valve so that each valve takes its share of the alternating-current load. The valves V1<111>, V2<111> and V3<111>, V4<111> are in parallel and the two pairs are in pushpull. The alternating-current input is applied through a transformer with a tapped secondary TS, and each grid is connected to a separate tapping on the secondary and through a separate resistance Rgl .. Rg4 to a source of bias potential B<11>. According to modifications, the input potentials are applied across a potentiometer with the tappings connected to the grids of the individual parallel-connected valves with means for adjusting the relative fixed grid bias, Figs. 1 and 6 (not shown) ; the input potentials are fed through a plurality of impedances, each with a tapping connected to the grid of a corresponding - valve, and the impedances are tapped at one end on a source of grid-bias potential, Fig. 3 (not shown). The circuit may be used for amplifying modulating currents.