GB435646A - Vacuum tube amplifiers - Google Patents

Abstract

435,646. Thermionic valves; valve amplifying circuits. STANDARD TELEPHONES & CABLES, Ltd., Connaught House, Aldwych, London.-(Assignees of Black, H. S. ; 820, Oak Avenue, Westfield, New Jersey, U.S.A.) Sept. 17, 1934, No. 26654. Convention date, Sept. 26, 1933. [Classes 39 (i) and 40 (v)] A valve has a cathode f, Fig. 2, an anode a, and, interposed between them, a grid c, two grids g, r mainly in the same surface, and grids s, p. When used as an amplifier, the grid c is connected as a space charge grid, grid g as a control grid, grid r as a space charge grid, grid s as a screen grid, and grid p as a suppressor grid. Such a valve C<3> is shown in Fig. 3, as the third valve of an amplifying circuit for a non-loaded multiplex-carrier telephone cable circuit, the first two valves A<2>, B<2> of which are screen grid tetrodes or pentodes. The input of the valve A<2> is connected across the arm 9 of a Wheatstone bridge 6 ..9 and the output transformer 12 is connected across a diagonal of a Wheatstone bridge the arms of which consist of the valve C<3> and resistances KRO, KR, R. A feed-back circuit for reducing the gain in the valve A<2> is connected across the other diagonal, and the amount of the feed-back is adjusted by a variable resistance 55 ; the feed-back is connected across a diagonal of the bridge 6.. 9. With this arrangement the feed-back is independent of the impedances of the incoming and load circuits. The Specification as open to inspection under Sect. 91 comprises also the following circuits (a) the first two valves are screen grid tetrodes and the third valve is similar to that shown in Fig. 3, but with the inner space charge grid and the suppressor grid omitted ; (b) all the valves are as in arrangement (a) with the addition of a suppressor grid in each valve, and (c) an arrangement similar to that in arrangement (a) but with an inner space charge grid in the third valve. This subject-matter does not appear in the Specification as accepted.