GB514361A - Improvements in and relating to amplifying circuits - Google Patents

Abstract

514,361. Automatic volume control. BRITISH THOMSON-HOUSTON CO., Ltd. Jan. 29, 1938, No. 2907. Void. Convention date, Jan. 30, 1937. [Class 40 (v)] For limiting large signal amplitudes or suppressing small, a double diode rectifier is used as an amplitude-responsive resistance. For the limitation of large signals in a line a, a<1>, c, c<1>, Fig. 1, a series resistance R is followed by a shunt transformer T1, the tapped secondary of which has its two portions shunted by the biased-back diodes I, II of a double diode D which become conducting at a predetermined signal amplitude. For suppressing signals of small amplitude a series transformer T, Fig. 4, shunted by diodes D, is followed by a shunt resistance R. In a modified limiting arrangement, Fig. 6, signals passing a line l, l<1> containing adjustable resistances R1, R2 are opposed by signals in the branch 2, 2<1>, 3, 3<1> when the biassedback diodes D become conducting for signals of above a predetermined amplitude. The diodes D may be arranged in the feed-back path of an amplifier V, Fig. 9, so that negative feed-back sets in when the diodes become conducting. The diodes may be provided with independently variable sources of grid bias and variable anode. resistances for accurate matching.