GB388292A - Improvements in or relating to thermionic amplifying arrangements - Google Patents

Abstract

388,292. Valve amplifying circuits. NAAMLOOZE VENNOOTSCHAP PHILIPS' GLOEILAMPENFABRIEKEN, 13D, Emmasingel, Eindhoven, Holland. July 18, 1932, No. 20320. Convention date, April 26. [Class 40 (v).] The grid bias of a valve amplifier varies with the signal volume, the bias becoming so much more negative as the volume diminishes that the sum of the bias and the signal voltage is practically constant. In this way the consumption of plate current is reduced and the efficiency increased. In Fig. 1, an electrolytic or other rectifier 3 is connected across the input coil 2 in series with two condensers 4, 5, and resistances 6, 7 are connected as shown. Permanent bias is supplied by a battery 8 whilst the rectified signal gives an opposing bias to the grid of the amplifier 1. In Fig. 2, the output of the amplifier 1 is divided by a condenser potentiometer 20, 21 and part is applied to a grid-leak rectifier 12. Rising signal strength gives increased positive voltage.on the plate of this rectifier, part of which is transferred to the. grid of the valve 1 through a potentiometer 14, 15, 16. Permanent bias is supplied by a battery 17, and alternating voltages are smoothed out by condensers 18, 19. In a third form, Fig. 3 (not shown), the battery 17 is replaced by a diode rectifier connected to a mains supply and the grid-leak rectifier 12 is replaced by a second diode rectifier, bothrectifiers being contained in a single envelope with a common cathode.