GB365011A - Improvements in or relating to thermionic amplifiers - Google Patents

Abstract

365,011. Valve amplifying and detecting circuits. BREY, H. W. K. DE, 93, Willem de Zwijgerlaan, The Hague. June 25, 1931, No. 18390. Convention date, July 11, 1930. [Class 40 (v).] In a direct-coupled valve amplifier (plate of first valve connected directly to grid of second valve), two separate sources of plate voltage are employed, the main source serving to supply both valves whilst the auxiliary source supplies additional plate voltage to the first valve only. As shown in the Figure, the first valve I is of t h e screen-grid type, and its plate is connected directly to the grid of the triode valve II, the plate circuit of the valve I including a high resistance 1. The second valve has its plate voltage supplied by a transformer 4, rectifier 6, and smoothing circuit 7, 8. An auxiliary source of plate voltage comprising transformer 3, rectifier 5, and smoothing circuit 11, 12, 12<1> creates a D.C. voltage at the points C, D which is added to that supplied by the other rectifier across the points D, E, and is applied across the cathode and plate of the first valve I. The common lead D of the two rectifying-systems is connected to the cathode of the second valve II. Thus the rectifier 6 supplies the heavy current required by the output valve, whilst the two rectifiers 5, 6 connected in series supply a higher voltage, but only a slight current, as required by the first valve I. An additional smoothing circuit 9, 9<1>, 10, 10<1> is included in the lead to the first valve. Grid bias for the valve I is provided by a resistance 13 in the cathode lead, and the screen grid is polarized by a connection to the lead D through a resistance 19. A single transformer may replace the separate units 3, 4 ; and the smoothing elements 7, 9, 91 may be connected in parallel, Fig. 3 (not shown).