GB650445A - Improvements in or relating to television circuit arrangements - Google Patents

Abstract

650,445. Television. MARCONI'S WIRELESS TELEGRAPH CO., Ltd. Feb. 18, 1946, No. 5093. Convention date, Nov. 29, 1944. [Class 40 (iii)] [Also in Group XL (c)] In a television circuit in which video signals including the D.C. component, are applied to a power amplifying valve from a cathodefollower coupling valve, a voltage regulator valve connected in parallel with the input circuit of the former valve provides compensation for the flow of grid current in said circuit and thus serves to maintain a predetermined bias on the grid of said power amplifying valve. Video signals from which the D.C. component has been removed are applied, after amplification in valve 17, to the grid 29 of the cathodefollower coupling valve 31 together with the D.C. component from the reinserting circuit comprising valve 35, condenser 41 and resistors 39, 47 and 49. The output signals of valve 31 developed across the cathode-resistor 57 are applied to the power amplifying valve 61 in parallel with the grid circuit of which is connected a regulator valve 63. The grid 71 of the regulator valve is supplied with a voltage from the D.C. reinserting circuit through resistor 75, the phase of which is the same as that of the signals applied to the grid 65 of the power amplifying valve. A current thus flows from cathode to anode in valve 63 when grid current flows in valve 61 and since these currents flow through resistor 57 so as to oppose each other the resulting variation across resistor 57 of the steady biassing voltage is zero.