GB520882A - Improvements in and relating to amplifier circuits - Google Patents

Abstract

520,882. Thermionic valve circuits; electron multipliers. VEREINIGTE GLUHLAMPEN UND ELEKTRIZITATS AKT.-GES. Sept. 30, 1938, No. 28452. Convention date, Sept. 30, 1937. [Classes 39 (i) and 40 (v)] In an amplifier circuit containing one or more electron-multiplier tubes (i) the no-load voltage on the multiplier electrodes exceeds 50 volts referred to the primary cathode in the first multiplier tube and with respect to the previous multiplier electrode for succeeding tubes, the no-load voltage being less than the working voltage, and (ii) the direct current from the multiplier electrode or electrodes is fed to the anode or anodes of an amplifier valve or valves in the circuit. A mains rectifier also supplies to these valves in parallel with the above supply; a saving in current is thereby effected. The multiplier tubes 1, 1<SP>1</SP>, 1<SP>11</SP>, Fig. 2, are arranged in cascade, the anode 5 of 1 being connected to the grid 31 of 11 ; the anode 5<SP>11</SP> of the last multiplier tube 1<SP>11</SP> is connected to the grid of the valve 20 whose anode is connected to the output-circuit terminal 0 and over resistance 31 and decoupling coils 19, 19<SP>1</SP>; 19<SP>11</SP> to the multiplier electrodes 6, 6<SP>1</SP>, 6<SP>11</SP>. The potential of the electrodes is derived from the auxiliary source V, the resistance 29 and the valve 20 forming a divider for the potential applied to the multiplier electrodes. In a modification (Fig. 3, not shown) a separate potential source is used for the multiplier electrodes and a stabilizing loading resistance 32 may be used in shunt to the valve 20 ; a loud speaker coil may be used as the resistance 32 or 29, Fig. 2. To compensate in the multiplier tubes for variations in the anode current/grid voltage characteristic following change in grid bias and consequent change of current to the multiplier electrode, the multiplier electrode 6, Fig. 4, besides connection to the positive line V is also connected to the cathode through resistance 33 so that the cathode resistance receives current from the electrode 6 ; drop in multiplier current will reduce the grid bias and raise primary current; the arrangement of such compensative multiplier tubes in an amplifier circuit is shown in a further Figure. The grid potential in the tube shown in Fig. 4 is determined by the connections to the supply V over the two resistances 7, 34.