GB333502A - Improvements in and relating to thermionic amplifying systems - Google Patents

Abstract

333,502. British Thomson-Houston Co., Ltd., (Gardiner, P. C.). Feb. 26, 1929, [Convention date]. Thermionic amplifiers. - A cascade-connected thermionic amplifier deriving its power supply from an alternating current source comprises a closed-loop resistance network including a potentiometer connected across the supply, and coupling, anode, and grid resistors. Fig. 1 shows a direct current amplifier having its signal input across leads 17, 18, the filaments being heated by alternating current. The H.T. supply from an alternating source 20 is fed to, the anode of the first valve through a resistor 25 and to the second valve through a relay or similar device 15. Valves 5 and 6 are connected in cascade through resistor 27, the grid of valve 6 being negatively biased by resistor 26 and a sliding contact 22 on potentiometer 21 forming a common anode and grid return to the filament circuit. The amplifier operates during each positive half.cycle, no anode current flowing during the negative halves. Valve 5 has a high amplification factor and suitable values for the various resistances are given. Fig. 2 (not shown) gives a circuit for an amplifier designed for alternating input signals, in which the input circuit 17, 18 has two resistors in parallel with a stopping condenser between them and in series with the grid lead. The first valve 5 thus acts as a rectifier; in other respects the circuit is identical with' that of Fig. 1.