GB717328A - Wide-band thermionic valve amplifier - Google Patents

Abstract

717,328. Valve amplifying circuits. MARCONI'S WIRELESS TELEGRAPH CO., Ltd. May 23, 1952 [Sept. 19, 1951], No. 21987/51. Class 40 (6) A wideband amplifier comprises main and auxiliary amplifiers A1, A2 respectively, Fig. 1, with mutually inverse frequency/attenuation characteristics, in which the signals el are applied to both and energy is also fed from the output of the auxiliary amplifier A1 to the input of the main amplifier, in phase with signal e1, so as to maintain the frequency/attenuation characteristic constant. Positive feedback may be applied to the auxiliary amplifier A2 and its frequency/ attenuation characteristic. determined by an output network R2, C2 which is the inverse of that, R1, Cl, of the main amplifier. Alternatively, Fig. 2 (not shown), the characteristics of the auxiliary amplifier may be determined by a stage provided with negative feedback from a cathode network having a frequency/attenuation characteristic similar to that of the main amplifier. In an embodiment, Fig. 3, the main amplifier V1 is cathode-driven from the auxiliary amplifier V2 and the valves are also coupled anode-to-grid by a network R4, C2, R2 having characteristics which are the inverse of those provided by the output resistance R1 and shunt stray capacity C1. In a further embodiment, Fig. 5, the valves V1, 2 are separately biased. by returning the grid leaks to tapping points on the common cathode resistance R3, and overall negative feedback is provided from a part, R5, of the load of a succeeding cathode-follower stage V3, being applied to the grid of valve V1 via a blocking condenser and resistance R2.