Nonlinear current mirrors for analog and mixed signal processing

An approach to designing nonlinear current mirrors for nonlinear functions is proposed in this paper. In a nonlinear current mirror, the ratio of input current to output one is made input-dependent in a controlled manner. This dependency is very useful in many applications, such as adaptive processing in analog circuits. Starting with an analysis of the basic structure of current mirror, the work presented in this paper comprises the general aspects of the design and the method to make the current ratio input-dependent in different manners. A design example is also presented. It is about a 3-transistor circuit performing a current amplification when the input current is low and an attenuation if it is high. With the rich variations of the device nonlinearity, varieties of nonlinear functions can be implemented in very simple current mirror circuits. Simulations results are provided to validate the designed function and to illustrate the effectiveness of the proposed design approach.