GB622491A - Improvements in electronic amplifiers - Google Patents

Abstract

622,491. Valve amplifying circuits. BRITISH THOMSON-HOUSTON CO., Ltd., and MACKENZIE, T. H. Sept. 26, 1946, No. 28799. [Class 40 (vi)] In a D.C. amplifier of the type wherein the input is used to modulate the input to an A.C. amplifier, the output being de-modulated, a fraction of the D.C. output is fed back in a negative sense into the D.C. input. A D.C. potential applied to resistor 2, Fig. 1, is supplied together with a feedback potential over resistor 9, to the upper contact of a switch 5 reversing at a rate of 50 times per second. The alternating component is fed to the grid of valve 4 over a blocking capacitor, an amplified and reversed output appearing at the anode. This potential is fed over capacitor 15 to a switch 14 operated synchronously with switch 5. The capacitor 11 assumes a steady potential, an amplified and inverted potential appearing across the output load 12. A fraction of the output potential is tapped off over the network 7, 8 and is applied over resistor 9 to reduce the effective input to the valve 4. In a modification, Fig. 3, the output load is in the cathode lead of valve 10 and is applied to the lower contact of switch 5. The effective capacity of capacitor 11 may be increased by connecting it between grid and anode, Fig. 4 (not shown), or between grid and earth, Fig. 5 (not shown), as appropriate. In a further modification, Fig. 6 (not shown), the switch 5, Fig. 1, is arranged to short the junction of resistors 2 and 9 to earth. In a further modification, Fig. 7 (not shown), the switch 14 is replaced by a non-linear resistor, a source of high frequency being switched to supply energy to the resistor in synchronism with the operation of switch 5. Specification 472,951 is referred to.