GB453886A - Valve amplifier for wide frequency bands such as are required in television - Google Patents

Abstract

453,886. Valve amplifying circuits. RADIOAKT.-GES. D. S. LOEWE, 10, Wiesenweg, Steglitz, Berlin. Dec. 20, 1934, No. 36494. Convention date, Dec. 20, 1933. [Class 40 (v)] In an amplifier for television and like wideband signals modulated on a carrier wave, low inter-stage coupling impedances are employed, and reaction is provided by a connection from the plate impedance (aperiodic or semi-aperiodic) of one valve to the grid of an earlier valve. As shown in Fig. 1, the second valve of a resistance-capacity-coupled pair has a resistance 4 in its plate circuit, a slider on which is connected through a condenser 6 to the grid of the first valve. The amplifier may constitute the intermediatefrequency stage of a superheterodyne receiver. The resistance 4 may be replaced by a coil 7 damped by a resistance 9 and tuned by its own capacity or by a condenser 8 to a desired frequency band, which should coincide with the optimum frequency of the amplifier without reaction. A further two-stage amplifier may be provided having a different optimum frequency; and the reaction may step over four valves. In Fig. 2, reaction is taken from a resistance 4 in the output circuit of an intermediate-frequency amplifier 24 to the oscillator grid 25 of a frequency-changing valve V by which the oscillation generated in the circuit 19, 20 is mixed with the incoming oscillation applied from the aerial 12 to the grid 17. As explained in Specification 450,247, owing to the valve V being already in oscillation at ultra-high frequency, there is less tendency for the reaction coupling 4, 6 to produce self-oscillation at the intermediate frequency. Alternatively, this advantage may be gained by conveying the reaction voltage to the grid of a valve oscillating at an auxiliary frequency. The Specification as open to inspection under Sect. 91 states that the reaction may take place over an odd number of valves if transformer couplings such as those described in Specification 446,346 are employed. It also states that the reaction system may be used for television signals not modulated on a carrier wave. This subject-matter does not appear in the Specification as accepted.