GB550907A - Improvements in or relating to push-pull amplifying circuits - Google Patents

Abstract

550,907. Thermionic valve circuits. PHILIPS LAMPS, Ltd. (Naamlooze Vennootschap Philips' Gloeilampenfabrieken). Jan. 13, 1942, No. 526. [Class 40 (v)] A push-pull paraphase amplifier comprises a valve 2 to the control grid of which the signal to be amplified is applied, and the anode circuit of which includes one half 31 of a primary winding 3 and a resistance 6 of such magnitude as to feed to the grid of a second valve 7 a voltage equal to the input but of opposite phase. The cathodes of the valves are connected together and the output is taken from terminals 5. The anode supply is taken from a full wave rectifier 9 and is smoothed by a resistance 11 and condensers C1 and 12. Grid bias for the valves is taken from a resistance R1, in the common cathode lead and is fed to the grid of 7 through a resistance R2, and to the grid of 2 after further smoothing. A bridge is constituted by the elements C1, Rl, R2, C2 and 6, which is fed at one pair of opposite apexes by the supply lines and the other apexes are connected to the grid and cathode respectively of valve 7. In order to prevent hum from being fed to the grid of valve 7 the bridge is balanced by making Cl, R1 = C2, R2, the resistance 6 being balanced by the C1. The grid bias resistances may be in the ohmic resistance of the electrolytic condenser separate cathode leads.