Note on the Design of Wide-Band Low-Noise Amplifiers

The case is considered of a grounded cathode amplifier fed from a finite source impedance in which the requirements of minimum noise factor conflict with those of adequate bandwidth. Equalization, either by feedback or by the use of complementary networks, provides one means of dealing with this problem, and involves modification of some circuit parameters for minimum noise factor. Design criteria are developed for amplifiers based on this procedure, including equalization of both input and tube coupling circuits. Some measurements on an experimental amplifier are reported.