Abstract
A new technique to improve the integral nonlinearity of the “linear-in-dB” variable gain amplifier (VGA) by adopting a piecewise linear transfer curve rather than a single curve is presented. The conventional single curve which is the first-order approximation of the exponential function yields bigger deviation errors as the gain control code advances. The integral nonlinearity (INL) of the proposed piecewise linear curve can be managed to be smaller because one of divisional curves moves to another before the deviation becomes prominent. A generic circuit schematic without chip size overhead is suggested with its future expansion in mind, and a design in a 0.35µm CMOS process under 3.3V supply is proposed and verified.
