CIRCUIT FOR LINEARLY GAIN CONTROLLING A DIFFERENTIAL AMPLIFIER

摘要

RCA 75,96 A circuit for linearly controlling the gain of a differential amplifier includes a differentially connected current splitter network biased by means of a symmetrical bias circuit coupled to a common operating potential and including first and second current sources with associated first and second impedances. The current splitter includes a diode exhibiting a non-linear voltage in response to linear current conduction, and a transistor. The bias circuit responds to a variable gain control voltage for causing the diode to conduct current which varies linearly with the gain control voltage. First and second mutually differential control voltages derived from the transistor and diode, including a non-linearly varying voltage exhibited by the diode, are applied to the differential amplifier for controlling the conduction of the differential amplifier linearly with respect to the original control voltage.