GB505492A - Electric wave amplifying systems - Google Patents

Abstract

505,492. Valve amplfying circuits. STANDARD TELEPHONES & CABLES, Ltd. Nov. 5, 1937, No. 30378. Convention date, Dec. 5, 1936. [Class 40 (v)] A wave translating system comprises amplifying and feedback paths, and a balancing impedance and a transformer associating the amplifying and feedback paths with the balancing impedance and the transmission path. The circuit includes two series connected windings of a hydrid coil one of the coils being connected between the amplifying path and the feedback path and the other between the feedback path and the balancing impedance. A third winding on the transformer is in the transmission path. The Figure shows an amplifier with hybrid transformers 45, 47 used in the input and output and two feedback paths 42, 43, the latter including a transformer so that either line L<1> or, line L, or both, may be unbalanced to ground. The feedback paths 42, 43 may be conjugate to one another and to the amplifier and to the input and output circuits. The feedbacks in the two paths may be adjusted one relatively to the other so that the singing tendency produced by one loop is prevented by feedback in the -other loop as described in. U.S.A. Specification 1,994,457. The input and output impedances may be balanced by networks 55, 60 as described in Specification 506,791. The couplings in the amplifier and in the feedback paths may have different cut-off frequencies so that stability may be obtained with increased feedback. A plurality of transformers may be included in the feedback loop one of which may contribute the major portion of the phase shift and gain change. The feedback paths may include a band elimination filter 50 and a transmission control network 51.