A programmable piecewise linear large-signal CMOS amplifier

A high-speed CMOS piecewise linear approximation circuit is presented that can be programmed for correction of nonlinearity after fabrication. The basic building block generates a linear segment, for which slope and position can be adjusted. Adjustments to adapt to arbitrary functions are done with floating gate devices fabricated in standard CMOS technology. The circuit is a voltage-to-current converter with an input range of the full power-supply voltage swing. In an implementation with 18 linear segments less than 0.15% error over rail-to-rail input range was achieved for a linear transfer function. Examples of strongly nonlinear transfer functions approximated to 0.5% accuracy are shown. The large-signal 3-dB frequency is 10 MHz. The implementations are done solely with 2-μm channel length devices