SE93267C1 - - Google Patents

Abstract

485,995. Valve amplifying circuits. TELEFONAKTIEBOLAGET L. M. ERICSSON. Dec. 2, 1937, No. 33339. Convention date, Dec. 3, 1936. [Class 40 (v)] In an amplifier using negative reaction designed for constant amplification over a wide frequency range, the output transformer is shunted by a resistance and capacity in series to prevent self-oscillation. The circuit shows a three valve amplifier in which to avoid undesired phase displacement the anode and grid impedances between the valves are divided into two parts A1, A2 and G1, G2 respectively, the mutually corresponding points being connected by coupling capacities K1, K2 of which K1 is smaller than K2. G1 is shunted by capacity C. The negative reaction coupling is taken out from a point between two resistances Ra shunted across the primary of output transformer Tu to form a voltage divider, the tapping being arranged so that ¢R/alpha=the internal resistance of valve E3 where R is the value of a resistance in the anode load and alpha is the fraction of the anode load tapped off by the reaction coupling. To avoid self-oscillation and phase displacement the primary of Tu is also shunted by resistance RK and capacity CK of such values that RK = #2LI/CK = n<2>Z where 2LI is the leakage inductivity measured from the primary side, n the transformation ratio of the transformer and Z the load impedance at the output side. Specification 482,328 is referred to.