Title :
Use of Feedback to Compensate for Vacuum-Tube Input-Capacitance Variations with Grid Bias
Author_Institution :
Hazeltine Service Corporation, Bayside, Long Island, New York
Abstract :
The input capacitance of amplifier tubes decreases with increasing grid bias, thereby detuning the input circuits of intermediate-frequency stages in a superheterodyne receiver. The phenomenon is caused by a shift in space charge and also by feedback through the grid-plate capacitance. The change in input capacitance is of the order of 1.5 micromicrofarads for each of the two causes. A simple form of feed-back coupling compensates for this change of capacitance. The grid-cathode capacitance and an unbypassed resistor in the cathode lead provide the feed-back coupling.
Keywords :
Capacitance; Cathodes; Coupling circuits; Electron tubes; Feedback; RLC circuits; Radiofrequency amplifiers; Resistors; Resonance; Space charge;
Journal_Title :
Radio Engineers, Proceedings of the Institute of
DOI :
10.1109/JRPROC.1938.228781
