GB463233A - Improvements in or relating to radio and other high frequency amplifiers and oscillators - Google Patents

Abstract

463,233. Valve amplifying and generating circuits. MARCONI'S WIRELESS TELEGRAPH CO., Ltd. July 29, 1936, No. 21014. Convention date, Oct. 7, 1935. [Class 40 (v)] In a high-frequency amplifier or oscillator a band-pass input circuit is provided and energy is fed back from the output of the amplifier to the band-pass input. The band-pass circuit is provided with a series resistance in the second oscillatory circuit from which the amplifier or oscillator is fed in such a manner that a 90‹ phase shift is produced in the feed-back circuit. Fig. 1 shows a feed-back circuit C0 L0 with the output from the filter taken across resistance R2. The valve V1 may be utilized only to give feed-back, Fig. 3 (not shown), or may also be utilized as an amplifier. Fig. 4 shows an arrangement in which the output is rectified and amplified to give automatic volume and selectivity control by variation of the bias of the valve V1. When a separate reaction valve is provided the bias of the grid may be controlled to adjust the selectivity, Fig. 5 (not shown). Fig. 7 shows an arrangement in which the volume control resistance R4 and the selectivity control resistance R3 are conjointly operated. Fig. 8 shows an automatic selectivity control of the bias of the reacting amplifier V1 in which as selectivity is increased the amplification of the valve V2 is decreased by bias control. Feed-back may be applied over a number of stages, Fig. 9, in which the phase changes between the stages is as shown. In a modification, Fig. 10 (not shown), each valve input is across a resistance so that in the limit all circuits are brought to zero resistance simultaneously.