Exponential function generator for automatic gain control

摘要

The circuit has a transistor pair (T1,T2) differential amplifier to which is applied an input signal (UE) that can be symmetrical or unsymmetrical. An output connects with a current mirror formed by a pair of transistors (T3, T4). A reference source (QR) provides a reference current (IR) that is divided into a branch current (IP) and remnant current (ID). The generated output current (IA) has an exponential characteristic up to a maximum value determined by the reference.