GB542356A - Improvements relating to electronic amplifiers - Google Patents

Abstract

542,356. Valve amplifying circuits. GROVES, W. W. (Automatic Signal Corporation). March 4, 1940, No. 4015. [A Specification was laid open to inspection under Sect. 91 of the Acts, Sept. 5, 1940.] [Class 40 (v)] The effect of voltage changes in the supply circuit is compensated by connecting a circuit comprising a condenser 13 and resistance 12 between a point on the H.T. supply circuit and the circuit connecting the anode of one valve to the grid of the next. In the pentode amplifier shown, the circuit 12, 13 is connected to a point on the supply potentiometer 14 shunted by condenser 18. The time constant of circuit 12, 13 is substantially equal to the time constant of the electron emission change in relation to the voltage supplying the heater coil of a standard pentode, which is of the order of four seconds. If the supply voltage rises, the filament heating current rises, and with some delay the current through the valve increases, thereby reducing the voltage on the anode which is transferred to the grid of the next valve; this reduction is compensated by an increased voltage applied through the circuit 12, 13. The electrodes of the valve 33 have their potentials determined by connection to the potentiometer 8, 7, 2, the values of these resistances being so chosen that a change in the potential applied to the anode is substantially compensated by the changes in the voltages applied to the grids. The compensation effected by the circuit 12, 13 may be incomplete and so chosen as to compensate the effects of variation of supply voltage on the next valve.