Design of adaptive voltage amplifiers with an input-DC-level-dependent gain

The DC component of a signal acquired from the environment often represents the information of the background that is useful in the processing of the component of small signal variations. In this paper, we propose a design method for adaptive voltage amplifiers, of which the gain for the voltage signal varies according to the DC component of the input. The basic circuit units used in the design are 3-transistor common-source amplifiers as such a circuit can be made to operate at a given bias point while the signal amplification gain is modulated by a varying DC component of the input. By using such simple units, one can implement sophisticated nonlinear characteristics of adaptive amplifiers while making the amplification linear at a given input DC level. A design example and the simulation results are also presented to demonstrate the effectiveness of the design method.