Automatic gain controlling circuit for recording and reproducing unit associated with magnetic head and free from relative accuracy between circuit components

摘要

An automatic gain controlling circuit is associated with magnetic heads for recording and reproducing pieces of video data information on a magnetic tape, and an in-phase current component is eliminated from a recording current flowing into one of the magnetic heads through a differential amplification between two input voltage levels produced from the recording current with the in-phase current component so that a gain control voltage signal is free from a relative accuracy between circuit components causative of the in-phase current component.