GB676787A - Improvements in and relating to amplifier circuits - Google Patents

Abstract

676,787. Valve amplifying circuits. BRITISH THOMSON-HOUSTON CO., Ltd. Aug. 16, 1949 [Aug. 28, 1948], No. 21336/49. Class 40 (vi) A wide-band amplifier comprises two valves connected in series across the H.T. supply, with inputs applied to grids in push-pull and the output taken between the junction of the valves and one side of the supply source, the push-pull inputs being taken from the anode and cathode of a single valve to whose input the signal is applied. As shown, an input, which may be a video signal or pulses, is applied to the grid of a phase-splitter valve 31, which supplies push-pull potentials to the grids of valves 41, 42 connected in series across the H.T. supply. With a positive-going rectangular pulse input, a negative pulse is applied to valve 41, while a positive pulse is applied to valve 42. A substantially rectangular negative-going pulse is produced across a capacitative load 44, since a vertical leading edge is produced by the rapid discharge of load 44 through the valve 42, and a vertical trailing edge is produced by the rapid charging of the load through valve 41. In order that the output pulse should be symmetrical, the anode and cathode resistors 34, 33 of phase-splitter 31 should be so proportioned that the voltage contributions of the valves 14, 42 are equal. This is achieved by making the inputs to valves 41, 42 inversely proportional to their gains, that is, by arranging that the cathode-to-grid potential of the valves is equal. A cathode resistor 43 may be included in the circuit of valve 42 to stabilize the circuit and compensate for inequalities in the characteristics of valves 41 and 42.