Improved Performances Linearization Technique for CMOS Differential Structure

An original differential structure using exclusively MOS devices working in the saturation region will be further presented. Performing the great advantages of an excellent linearity (for an extended range of the input voltage), obtained by compensating the quadratic characteristic of the MOS transistor operating in the saturation region by an original square-root circuit, the proposed circuit is designed for low-voltage low-power operation. The frequency response of the new differential structure is strongly increased by operating all the MOS devices in the saturation region. The circuit is implemented in 0.35 mum CMOS technology, the SPICE simulations confirming the theoretical estimated results (a linearity error under a percent for an extended input range of plusmn0.5V and a supply voltage corresponding to low-voltage requirements, V_cc = 3 V).