Variable gain equalizer with a mirror circuit having opposite phase relationship between input and output currents

摘要

A variable gain equalizer comprises an equalizing network having an impedance element coupled between an input terminal to which an input voltage is applied and an output terminal. A potentiometer is provided having first and second mutually complementarily variable resistance portions divided by a slidable tap having an inherent contact resistance connected to ground. The first and second portions of the potentiometer are coupled in the equalizing network in series with the impedance element. An inversion type current mirror curcuit causes an input alternating current to flow as a function of the input voltage in the contact resistance of the potentiometer through the first resistance portion and causes an output alternating current of equal amplitude to, but opposite phase to, the input alternating current to flow in the contact resistance through the second resistance portion and impedance element to the output terminal.