GB623213A - Improvements in or relating to electron discharge tube neutralising circuit arrangements - Google Patents

Abstract

623,213. Valve amplifying circuits. SADIRCARPENTIER. Oct. 25, 1946, No. 31793. Convention date, Jan. 26, 1943. [Class 40 (vi)] A circuit for neutralizing the grid-anode capacity of a thermionic valve by means of a balanced capacity bridge has a resonant input circuit associated with the bridge constituted by an inductor tuned with two series capacitors, the point between which is at a fixed potential, the input circuit being coupled to the preceding stage at the end opposite to that which is coupled to the control grid of the neutralized stage. The Figure shows a neutralized triode valve 8, the grid-anode capacity 1 and capacitors 4, 5 and 6 being arranged in a balanced bridge circuit. The inductor 2 resonates with capacitors 4, 5, either the capacitors being made variable and tuning conjointly or the inductor being of the movable core variable inductance type. Bias for control grid 7 is supplied through the decoupled choke 17 and the input to the resonant circuit is derived from anode 13 to which H.T. is fed through choke 14. The ratio of the reactance of chokes 14, 17 is preferably made equal to the ratio of capacitances 4, 5. Within the operating range the impedances of capacitors 9, 16 are preferably negligible compared with those of chokes 14, 17 and with the internal resistance of the valve having anode 13. The resonant frequencies of the chokes 14, 17 are outside the range of frequencies which the stage is required to handle. Specification 292,716, [Class 40 (v)], is referred to.