On the Realization of Current-Mode Four-Quadrant CMOS Fractional Power and Cube-Root Converter

A new current-mode fractional-power CMOS circuit such as cube-root and squared-cube-root configurations that give output signal in four quadrants has been presented for the first time. MOSFETs utilized in the design exploit translinear principle in weak-inversion region. The second-order effects on the circuit proposition have been analysed. The implementation justification has been validated by post-layout simulation on Virtuoso-SPECTRE tool with 180 nm GPDK CMOS process parameters. It has been found that using ± 0.5 V supply voltage, the realized cube-root and squared-cube-root circuits work for an input range of ± 30 µA while consuming few hundred nano-watts of static power and exhibit a maximum of ± 1 dB error over a wide input range of ± 1.5 µA to ± 30 µA in all four quadrants. Utility of the proposed circuits, as companding and gamma corrector, has also been elaborated.