Integrated circuit for generating a temperature independent, dynamically

Abstract

A temperature independent, dynamically compressed, DC control voltage is obtained by converting by means of a converter circuit employing a current mirror, a linear variation of the voltage across a control potentiometer, external to the integrated circuit, in a logarithmic differential voltage between two output voltage terminals, respectively on a first and a second branch of the converter circuit, the voltage signal taken from the first branch of the converter circuit being fed to the input of a unitary gain stage biased by a current generator with a temperature coefficient corresponding to the reciprocal of the temperature coefficient of integrated resistances and the corresponding output signal of the unitary gain stage being fed to a first input of a differential stage, to the second input of which is fed the signal taken from the second branch of the converter circuit. The differential stage being also biased by a current generator with a temperature coefficient equal to the reciprocal of the temperature coefficient of integrated resistances and having an integrated load resistance connected between the supply rail and the output terminal of the differential stage on which the desired temperature independent and dynamically compressed control voltage is produced. The circuit is particularly useful for generating a gain control current in an AGC system.