GB307544A - Improvements in or relating to thermionic amplifiers - Google Patents

Abstract

307,544. Smith, W. S., and McLachlan, N. W. Dec. 10, 1927. Thermionic amplifiers.-In order to compensate for initial distortion due to attenuation of the side-band frequencies occurring in the highfrequency stages of amplification in a modulated carrier-wave receiver, the output circuit of a subsequent valve carrying low-frequency or rectified components is shunted by a tuned circuit or equivalent impedance network, which emphasises the voltage of those frequencies previously diminished, thereby restoring the average overall response. As shown in Fig. 6, a condenser 5 by-passes the carrier in combination with output chokes 6, 10. A variable resistance 7 is inserted in series with a parallel-tuned circuit 8, 9 across the output chokes. The tuned circuit 8, 9 mav be shunted by a resistance or capacity, whilst the inductance 8 may be replaced by a transformer or auto-transformer. The condenser 5 and choke 6 may be duplicated. As shown, the attenuation - correcting network 5 - - 10 is followed by a four-electrode or screened-grid valve 18 of high amplification factor, a choke 21 being included in the plate circuit to prevent back-coupling through the batteries. The invention is applicable to the output circuit of the first or second detector in a heterodyne or supersonic receiver.