Voltage controlled variable gain amplifier circuit

摘要

This invention provides a voltage controlled variable gain amplifier circuit that varies its gain linearly and continuously against a gain control voltage VC. The voltage controlled variable gain amplifier circuit includes a first differential amplifier, a second differential amplifier, a gain control voltage/current conversion circuit and a reference current generation circuit. The first differential amplifier and the second differential amplifier are connected in series. The gain control voltage/current conversion circuit converts the gain control voltage VC into a gain control current IC that varies linearly against the gain control voltage VC. Drain currents Id1 and Id2 of first and second differential input transistors vary linearly against the gain control current IC.