Fully integrated programmable Howland current source for sensors excitation

Abstract

In this paper a fully integrated implementation of the classical Howland current source is presented as a compact solution for exciting resistive and piezoresistive sensors. This circuit, which is part of a programmable signal conditioning microsystem, described elsewhere, is treated as a module that is capable of providing a voltage-adjustable current whose full-scale is 10 mA. Experimental results from samples manufactured in 0.8 /spl mu/m CMOS have shown that the circuit features a full-scale nonlinearity of 0.042% powered by a supply voltage of 5 V. The measured frequency response using a 50 /spl Omega/ resistive load rolls off at 228 kHz, which is in excess of the predicted applications.