GB629640A - Improvements in or relating to apparatus for controlling electrical signals - Google Patents

Abstract

629,640. Pulse circuits. CINEMA-TELE. VISION, Ltd., and GRAHAM, G. E. G. May 15, 1947, No. 13107. [Class 40 (vi)] An amplifier whose output may be varied to be either in phase or in antiphase with the input comprises a valve in which the anode current/signal grid voltage characteristic is alternatively of positive or negative slope, according to the potential applied to a second control electrode of the valve, a fraction of this potential being applied also to the signal grid to prevent spurious changes of anode potential. In the embodiment of Fig. 2, a train of pulses is applied to the grid of a screen-grid valve over a blocking condenser 6 and an amplified train in which alternate pulses are reversed in sign is obtained from the anode circuit by switching the screen potential between values giving positive and negative slope. The screen potential is switched by means of a rectangular control wave applied over a blocking condenser 10, the mean potential being held at a suitable value by a series resistance 11 connected to the positive supply. The control wave is prevented from appearing in amplified form in the anode circuit by applying a fraction to the signal grid over resistance network 7, 8, 12. The valve characteristic is linearized by means of an unbyepassed cathode resistance 13, and valves in which the anode is specially treated to have high secondary emission may be used.