Digitally programmable dB-linear CMOS AGC for mixed-signal applications

Central to the design of a high-performance, high-dynamic mixed-signal interface circuitry is the design of a linear (in the db scale) automatic gain control (AGC) loop. Achieving this db-linear characteristic requires an exponential function and is therefore, not straightforward to implement with CMOS devices in strong inversion. The article in this column discusses a simple CMOS circuit design solution to this problem, The design is also digitally controlled, which should help in designing simple mixed-signal interfaces with low power consumption and less chip area.