GB827956A - Improvements relating to electrical circuit arrangements for generating voltages of rectangular waveform - Google Patents

Abstract

827,956. Inverting. BRITISH THOMSONHOUSTON CO. Ltd. March 9, 1956 [Jan. 12, 1955; June 21, 1955], Nos. 988/55 and 17953/55. Class 38 (2). [Also in Group XL (c)] An inverter comprises two electric discharge tubes biased to be normally conducting with alternating current applied to their grids so that the tubes alternately conduct and are cut off. Square waves are generated in the output of a transformer which is differentially connected to the output circuit of the tubes having an amplitude dependent upon an independent D.C. control voltage applied to their grids. Fig. 1 shows a squarewave generator in which an AC supply is connected via input transformers to the control grids of the two halves of double triode tube 1 the tubes having a common cathode resistor R so that the tubes are normally conducting. The grids are also connected to a DC control source and rectifiers 2, 3 are connected across the input transformer secondaries so that the tubes conduct on alternate half-cycles of the AC supply and a square-wave form appears at the output terminals, the amplitude of which may be adjusted by variation of the D.C. control source. In a modification, Fig. 2 (not shown), the rectifiers are connected in series with the secondary winding of the input transformers and resistors are connected across the winding. In a further modification, Fig. 3 (not shown), the output pulses are taken from across the transformer which is fed from the cathode circuits of the two triodes. In a modification shown in Fig. 4, negative feed-back is provided between the output transformer and the control grid circuit of the two tubes thus minimizing any drift of the output. In a further modification, Fig. 5 (not shown), the negative feed-back is effected by a single winding on the output transformer connected to a bridge rectifier circuit to feed-back D.C. to the control grid circuits of both tubes. Pentode tubes may be used as shown in Fig. 6, the D.C. control voltage being fed to the control grids of each tube and the A.C. input voltage being fed via transformers to the suppressor grid. The negative-going swing of the screen grids may be limited by means of a diode, Fig. 6a (not shown). A separate hightension supply may be effected to the screen grids of the two tubes, Fig. 6b (not shown).