GB577801A - Improvements in and relating to voltage responsive thermionic valve circuit arrangements - Google Patents

Abstract

577,801. Valve amplifying circuits. MORRIS, D. G. O., and METROPOLITANVICKERS ELECTRICAL CO., Ltd. April 16, 1943, No. 6158. [Class 40 (v)] [Also in Group XXXVI] A circuit arrangement adapted to provide an output quantity which is dependent in magnitude and sense on the difference between two input voltages comprises a pair of thermionic valves having separate anode resistors and a common cathode resistor and associated with circuit elements across the anode /cathode of one of the valves to form a potential dividing circuit such that the voltage across the potentiometer is so resolved at the intermediate point that the potential remains constant with corresponding variation in the anode currents of both valves but varies with the difference between the anode currents. The Figure shows an arrangement in which input voltages V 1, V 2 are applied through current limiting resistances 1, 2 to the grids of triodes T1, T2, these are associated with the anode resistances 5 and 6 and a common cathode resistance 12 and potentiometers 17, 18, 19, 20 so that voltages applied between the grids produce potentials between the points 21, 22. A potentiometer 10 between the cathodes is provided initially to adjust the valves so that to equalize the slopes of the operative parts of the anode current grid voltage characteristics. A resistor 16 in the cathode heating circuit is provided so that when the slopes have been equalized the currents may be equalized. The output voltages are preferably amplified by the valves A1, A2 and may be applied to a moving coil instrument F to provide a deflection showing the difference and the sense of the voltages V1, V2.