A novel low-voltage integrated interface for sensor signal processing

In this paper, the design of a novel integrated interface for sensor signal processing is presented. It has been designed in a standard low-cost CMOS technology (Mietec 0.5 μm), so to completely operate at a low supply voltage (± 1 V), typical for portable applications, as in sensors and biomedical fields. The circuit topology has been implemented so that all the electrical characteristics are independent of the supply voltage value and almost of the temperature variations. The input stage is a rail-to-rail constant-Gm low-voltage preamplifier, showing low noise (13 nV/(Hz)¹2/) and low offset (< 1 mV). A theoretical study has been conducted to determine the input transistor aspect ratios which ensure the minimum noise characteristics. After another amplifying stage, an analog-to-digital converter has been also designed, at transistor level, for these low supplies. The whole circuit can be integrated in a single chip and shows a total power dissipation as low as 4 mW.