GB382307A - Improvements relating to thermionic valve amplifiers - Google Patents

Abstract

382,307. Valve circuits for wireless reception. IGRANIC ELECTRIC CO., Ltd., 147, Queen Victoria Street, and PADDLE, L. H., 2, Burlington Gardens, Chiswick, both in London. July 23, 1931, No. 21058. [Class 40 (v).] A multivalve amplifier is characterized by the feature that the output or coupling impedance is located between the cathode and the negative pole of the H.T. supply, and by the feature that the H.T. supply is common to both valves. In Fig. 1 the primary winding 4a of the intervalve coupling is on the cathode side of the H.T. source 3, but is not in the input circuit of the valve 1a. Resistances 6a, 6b provide grid-bias for the two valves 1a, 1b. The filaments are energized by separate windings on the supply transformer 10. In Fig. 3 the valves 1a, 1b are anode-coupled in the ordinary way, whilst the output valve 1c is cathodecoupled to the loud-speaker through a coil 4c. In Fig. 4 the valves la, 1b are cathode-coupled, and by adjusting the value of the coupling- impedance 4a, 16, grid current flowing in the valve 1b can be counterbalanced by the anode current from the valve 1a, so that the valve will amplify over a positive grid-voltage swing without distortion. Fig. 7 shows a push-pull arrangement in which the output from the two valves 1a is cathode-coupled to the valves 1b, and grid current is again neutralized. The Provisional Specification also describes a singlevalve amplifier with a cathode-coupled output.