An On-Chip Linear, Squaring, Cubic and Exponential Analog Function Generator

This paper presents a novel technique based on the current steering technique for the generation of a reconfigurable current that approximates the linear, squaring, cubic, and exponential and their descending analog functions. The proposed implementation can be easily programmed to generate these functions by simply reconfiguring the weighting factors of current sources and offers an extendable input voltage range keeping excellent accuracy. The circuit topology has been fabricated using $0.18~\mu \text{m}$ TSMC CMOS process under 1.8 V supply voltage. Measurements results validate the theoretical analysis giving for 400 mV input voltage range while keeping small relative approximation errors, 0.3%, 1%, 1.9%, and 0.7% for linear, squaring, cubic, and exponential, respectively.