GB409360A - Improvements in alternating current signal generators and amplifiers - Google Patents

Abstract

409,360. Impedance networks. RYALL, L. E., 52, Crescent Gardens, Eastcote, Ruislip, Middlesex. Oct. 31, 1932, Nos. 30506/32, 34722/32, and 3/33. [Classes 40 (iii) and 40 (v).] Distortion of signals is neutralized by means of a network containing dry-plate rectifiers located in an A.C. circuit and adapted to produce distortion equal and opposite to that from which the signals suffer. Thus a triode amplifier, in which output is related to input as the ordinates to the abscissµ in Fig. 1 (3/33), may be corrected so as to produce a linear overall characteristic by the insertion in its input or output circuit of a network comprising a rectifier and resistances, as shown in Figs. 4 and 5 (3/33). The rectifiers 1 and 3 may be replaced by pairs of oppositely directed rectifiers connected in parallel with one another if a pentode valve is to be corrected, Figs. 2, 6, 7 ( 3 /33 ) (not shown), or in series with one another if a push-pull pair of valves is to be corrected, Figs. 3, 8, 9 (3 /33) (not shown). The compensating network is preferably connected at a point in the system where the effect of the system on phase-change is the same for all frequencies ; alternatively one of the resistances shown may be shunted by a condenser to compensate for unequal changes of phase. To produce unequal distortion in positive and negative half-cycles, a further resistance may be connected in series or parallel with one member of a pair of rectifiers. In a telephone repeater used for amplifying two or more speech channels simultaneously (e.g. one comprising frequencies from 300 to 2500 and the other from 3000 to 5500) the corrector circuit 8, 9, is included in the output transformers to compensate for any distortion introduced by the second valve 5. Gain is controlled by means either of tappings on a potentiometer 4, or of tappings on a transformer 2 in combination with a condenser 6 which gives increased gain at high frequencies. Since distortion introduced by the first valve 3 cannot be compensated by the network 8, 9, such distortion is reduced by the use of a large anode impedance 10 ; and a grid condenser 12 may be used to compensate for distortion due to internal capacity of the second valve 5. Phase-distortion due to leakage inductance in the transformer 13 is compensated by means of a high-impedance choke 14 in the anode circuit of valve 5 ; and to compensate for loss of gain at low frequencies the anode resistance 10 of the first valve 3 may be shunted by a resistance and condenser 16, 17.