A Constructive Methodology of Analog Synthesis of Nonlinear Functions in Subthreshold CMOS

Abstract

We introduce a clear constructive methodology of approximation and synthesis of analog functions using the transfer characteristics of the basic differential pair. The new methodology provides circuit designers with an easy-to-understand solution of the function approximation problem employing MOSFETs in weak inversion. It further provides compact formulas for the optimal coefficients involved in the approximation. We confirm the design methodology using SPICE through two examples involving the exponential function.