GB506081A - Improvements in or relating to multi-stage thermionic valve amplifiers - Google Patents

Abstract

506,081. Valve amplifying circuits. GENERAL ELECTRIC CO., Ltd., and FARREN, L. I. Jan. 24, 1938, No. 2261. [Class 40 (v)] In an amplifier covering a wide-band of frequencies, instead of using inductance in series with the load resistance to prevent loss of the higher frequencies in some of the stages, two consecutive stages comprise screen-grid valves VI, V2 of mutual conductance g<1>, g<2> the second of which has feedback produced by a resistance R5 between grid and anode while the load R1 of the first valve is substantially equal to G<1>R<5>/g2R2(g1R5-G<1>) where R2 is the load of the second stage and G<1> the gain of the two stages. The Figure shows the circuit wherein, preferably G<1>=g1g2 R2<SP>2>/# where # is the ratio of the stray capacity shunting R1 to that shunting R2, and R5 lies between 1À7g2 R2<SP>2>/# and g2R2<SP>2> /# and preferably R5=1À1g2R2<SP>2>/#, and R1=R2/(#-alpha) where alpha=g2R2<SP>2>/R5. The Specification gives a mathematical analysis of the circuit and the Provisional Specification in addition gives curves showing the change in response as R5 is varied. The amplifier may be direct-coupled, condensers C23, CO1 being omitted when the operating range includes very low or zero frequencies.