Nonlinear Tuned Circuits

An application of a ferrite core variable inductance is illustrated in an active amplifier feedback circuit. By this means a lock-on response of the amplifier to a drifting operating frequency was obtained over a wide bandwidth (62-82kHz when tuned to a 75-kHz carder). Without a full analysis of the dynamics of feedback control systems incorporating semi-saturated ferrite cores available only the results of some initial experiments are given.